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postgresql/src/backend/optimizer/plan/planagg.c

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Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
/*-------------------------------------------------------------------------
*
* planagg.c
* Special planning for aggregate queries.
*
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
* This module tries to replace MIN/MAX aggregate functions by subqueries
* of the form
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
* (SELECT col FROM tab
* WHERE col IS NOT NULL AND existing-quals
* ORDER BY col ASC/DESC
* LIMIT 1)
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
* Given a suitable index on tab.col, this can be much faster than the
pgindent run for 9.4 This includes removing tabs after periods in C comments, which was applied to back branches, so this change should not effect backpatching.
2014-05-06 18:12:18 +02:00
* generic scan-all-the-rows aggregation plan. We can handle multiple
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
* MIN/MAX aggregates by generating multiple subqueries, and their
pgindent run for 9.4 This includes removing tabs after periods in C comments, which was applied to back branches, so this change should not effect backpatching.
2014-05-06 18:12:18 +02:00
* orderings can be different. However, if the query contains any
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
* non-optimizable aggregates, there's no point since we'll have to
* scan all the rows anyway.
*
*
Update copyright via script for 2017
2017-01-03 19:48:53 +01:00
* Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
Remove cvs keywords from all files.
2010-09-20 22:08:53 +02:00
* src/backend/optimizer/plan/planagg.c
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
Split tuple struct defs from htup.h to htup_details.h This reduces unnecessary exposure of other headers through htup.h, which is very widely included by many files. I have chosen to move the function prototypes to the new file as well, because that means htup.h no longer needs to include tupdesc.h. In itself this doesn't have much effect in indirect inclusion of tupdesc.h throughout the tree, because it's also required by execnodes.h; but it's something to explore in the future, and it seemed best to do the htup.h change now while I'm busy with it.
2012-08-30 22:15:44 +02:00
#include "access/htup_details.h"
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
#include "catalog/pg_aggregate.h"
#include "catalog/pg_type.h"
#include "nodes/makefuncs.h"
Move exprType(), exprTypmod(), expression_tree_walker(), and related routines into nodes/nodeFuncs, so as to reduce wanton cross-subsystem #includes inside the backend. There's probably more that should be done along this line, but this is a start anyway.
2008-08-26 00:42:34 +02:00
#include "nodes/nodeFuncs.h"
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
#include "optimizer/clauses.h"
#include "optimizer/cost.h"
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
#include "optimizer/pathnode.h"
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
#include "optimizer/paths.h"
#include "optimizer/planmain.h"
#include "optimizer/subselect.h"
Fix generation of MergeAppend plans for optimized min/max on expressions. Before jamming a desired targetlist into a plan node, one really ought to make sure the plan node can handle projections, and insert a buffering Result plan node if not. planagg.c forgot to do this, which is a hangover from the days when it only dealt with IndexScan plan types. MergeAppend doesn't project though, not to mention that it gets unhappy if you remove its possibly-resjunk sort columns. The code accidentally failed to fail for cases in which the min/max argument was a simple Var, because the new targetlist would be equivalent to the original "flat" tlist anyway. For any more complex case, it's been broken since 9.1 where we introduced the ability to optimize min/max using MergeAppend, as reported by Raphael Bauduin. Fix by duplicating the logic from grouping_planner that decides whether we need a Result node. In 9.2 and 9.1, this requires back-porting the tlist_same_exprs() function introduced in commit 4387cf956b9eb13aad569634e0c4df081d76e2e3, else we'd uselessly add a Result node in cases that worked before. It's rather tempting to back-patch that whole commit so that we can avoid extra Result nodes in mainline cases too; but I'll refrain, since that code hasn't really seen all that much field testing yet.
2013-11-07 19:13:12 +01:00
#include "optimizer/tlist.h"
Alphabetically order reference to include files, "N" - "S".
2006-07-11 19:26:59 +02:00
#include "parser/parsetree.h"
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
#include "parser/parse_clause.h"
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
#include "rewrite/rewriteManip.h"
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
#include "utils/lsyscache.h"
#include "utils/syscache.h"
static bool find_minmax_aggs_walker(Node *node, List **context);
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
static bool build_minmax_path(PlannerInfo *root, MinMaxAggInfo *mminfo,
Oid eqop, Oid sortop, bool nulls_first);
Postpone creation of pathkeys lists to fix bug #8049. This patch gets rid of the concept of, and infrastructure for, non-canonical PathKeys; we now only ever create canonical pathkey lists. The need for non-canonical pathkeys came from the desire to have grouping_planner initialize query_pathkeys and related pathkey lists before calling query_planner. However, since query_planner didn't actually *do* anything with those lists before they'd been made canonical, we can get rid of the whole mess by just not creating the lists at all until the point where we formerly canonicalized them. There are several ways in which we could implement that without making query_planner itself deal with grouping/sorting features (which are supposed to be the province of grouping_planner). I chose to add a callback function to query_planner's API; other alternatives would have required adding more fields to PlannerInfo, which while not bad in itself would create an ABI break for planner-related plugins in the 9.2 release series. This still breaks ABI for anything that calls query_planner directly, but it seems somewhat unlikely that there are any such plugins. I had originally conceived of this change as merely a step on the way to fixing bug #8049 from Teun Hoogendoorn; but it turns out that this fixes that bug all by itself, as per the added regression test. The reason is that now get_eclass_for_sort_expr is adding the ORDER BY expression at the end of EquivalenceClass creation not the start, and so anything that is in a multi-member EquivalenceClass has already been created with correct em_nullable_relids. I am suspicious that there are related scenarios in which we still need to teach get_eclass_for_sort_expr to compute correct nullable_relids, but am not eager to risk destabilizing either 9.2 or 9.3 to fix bugs that are only hypothetical. So for the moment, do this and stop here. Back-patch to 9.2 but not to earlier branches, since they don't exhibit this bug for lack of join-clause-movement logic that depends on em_nullable_relids being correct. (We might have to revisit that choice if any related bugs turn up.) In 9.2, don't change the signature of make_pathkeys_for_sortclauses nor remove canonicalize_pathkeys, so as not to risk more plugin breakage than we have to.
2013-04-29 20:49:01 +02:00
static void minmax_qp_callback(PlannerInfo *root, void *extra);
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
static Oid fetch_agg_sort_op(Oid aggfnoid);
/*
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
* preprocess_minmax_aggregates - preprocess MIN/MAX aggregates
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
*
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
* Check to see whether the query contains MIN/MAX aggregate functions that
* might be optimizable via indexscans. If it does, and all the aggregates
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
* are potentially optimizable, then create a MinMaxAggPath and add it to
* the (UPPERREL_GROUP_AGG, NULL) upperrel.
*
* This should be called by grouping_planner() just before it's ready to call
* query_planner(), because we generate indexscan paths by cloning the
* planner's state and invoking query_planner() on a modified version of
* the query parsetree. Thus, all preprocessing needed before query_planner()
* must already be done.
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
*
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
* Note: we are passed the preprocessed targetlist separately, because it's
* not necessarily equal to root->parse->targetList.
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
*/
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
void
preprocess_minmax_aggregates(PlannerInfo *root, List *tlist)
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
{
Remove planner's private fields from Query struct, and put them into a new PlannerInfo struct, which is passed around instead of the bare Query in all the planning code. This commit is essentially just a code-beautification exercise, but it does open the door to making larger changes to the planner data structures without having to muck with the widely-known Query struct.
2005-06-06 00:32:58 +02:00
Query *parse = root->parse;
Fix a performance regression in 8.2: optimization of MIN/MAX into indexscans had stopped working for tables buried inside views or sub-selects. This is because I had gotten rid of the simplify_jointree() preprocessing step, and optimize_minmax_aggregates() wasn't smart enough to deal with a non-canonical FromExpr. Per gripe from Bill Howe.
2007-02-06 07:50:26 +01:00
FromExpr *jtnode;
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
RangeTblRef *rtr;
RangeTblEntry *rte;
List *aggs_list;
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
RelOptInfo *grouped_rel;
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
ListCell *lc;
/* minmax_aggs list should be empty at this point */
Assert(root->minmax_aggs == NIL);
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
/* Nothing to do if query has no aggregates */
Remove planner's private fields from Query struct, and put them into a new PlannerInfo struct, which is passed around instead of the bare Query in all the planning code. This commit is essentially just a code-beautification exercise, but it does open the door to making larger changes to the planner data structures without having to muck with the widely-known Query struct.
2005-06-06 00:32:58 +02:00
if (!parse->hasAggs)
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
return;
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
Phase 2 of pgindent updates. Change pg_bsd_indent to follow upstream rules for placement of comments to the right of code, and remove pgindent hack that caused comments following #endif to not obey the general rule. Commit e3860ffa4dd0dad0dd9eea4be9cc1412373a8c89 wasn't actually using the published version of pg_bsd_indent, but a hacked-up version that tried to minimize the amount of movement of comments to the right of code. The situation of interest is where such a comment has to be moved to the right of its default placement at column 33 because there's code there. BSD indent has always moved right in units of tab stops in such cases --- but in the previous incarnation, indent was working in 8-space tab stops, while now it knows we use 4-space tabs. So the net result is that in about half the cases, such comments are placed one tab stop left of before. This is better all around: it leaves more room on the line for comment text, and it means that in such cases the comment uniformly starts at the next 4-space tab stop after the code, rather than sometimes one and sometimes two tabs after. Also, ensure that comments following #endif are indented the same as comments following other preprocessor commands such as #else. That inconsistency turns out to have been self-inflicted damage from a poorly-thought-through post-indent "fixup" in pgindent. This patch is much less interesting than the first round of indent changes, but also bulkier, so I thought it best to separate the effects. Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
2017-06-21 21:18:54 +02:00
Assert(!parse->setOperations); /* shouldn't get here if a setop */
Assert(parse->rowMarks == NIL); /* nor if FOR UPDATE */
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
/*
* Reject unoptimizable cases.
*
Support window functions a la SQL:2008. Hitoshi Harada, with some kibitzing from Heikki and Tom.
2008-12-28 19:54:01 +01:00
* We don't handle GROUP BY or windowing, because our current
8.4 pgindent run, with new combined Linux/FreeBSD/MinGW typedef list provided by Andrew.
2009-06-11 16:49:15 +02:00
* implementations of grouping require looking at all the rows anyway, and
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
* so there's not much point in optimizing MIN/MAX.
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
*/
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
if (parse->groupClause || list_length(parse->groupingSets) > 1 ||
parse->hasWindowFuncs)
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
return;
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
Prevent planagg.c from failing on queries containing CTEs. The existing tests in preprocess_minmax_aggregates() usually prevent it from trying to do anything with queries containing CTEs, but there's an exception: a CTE could be present as a member of an appendrel, if we flattened a UNION ALL that contains CTE references. If it did try to generate an optimized path for a query using a CTE, it failed with "could not find plan for CTE", as reported by Torsten Förtsch. The proximate cause is an unwise decision in commit 3fc6e2d7f to clear subroot->cte_plan_ids in build_minmax_path(). That left the subroot's cte_plan_ids list out of step with its parse->cteList. Removing the "subroot->cte_plan_ids = NIL;" assignment is enough to let the case work again, but really it's pretty silly to be expending any cycles at all in this module when there are CTEs: we always treat their outputs as unordered so there's no way for the optimization to win. Hence, also add an early-exit test so we don't waste time like that. Back-patch to 9.6 where the misbehavior was introduced. Report: https://postgr.es/m/CAKkG4_=gjY5QiHtqSZyWMwDuTd_CftKoTaCqxjJ7uUz1-Gw=qw@mail.gmail.com
2016-12-13 19:20:16 +01:00
/*
* Reject if query contains any CTEs; there's no way to build an indexscan
* on one so we couldn't succeed here. (If the CTEs are unreferenced,
* that's not true, but it doesn't seem worth expending cycles to check.)
*/
if (parse->cteList)
return;
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
/*
Standard pgindent run for 8.1.
2005-10-15 04:49:52 +02:00
* We also restrict the query to reference exactly one table, since join
* conditions can't be handled reasonably. (We could perhaps handle a
* query containing cartesian-product joins, but it hardly seems worth the
Revisit handling of UNION ALL subqueries with non-Var output columns. In commit 57664ed25e5dea117158a2e663c29e60b3546e1c I tried to fix a bug reported by Teodor Sigaev by making non-simple-Var output columns distinct (by wrapping their expressions with dummy PlaceHolderVar nodes). This did not work too well. Commit b28ffd0fcc583c1811e5295279e7d4366c3cae6c fixed some ensuing problems with matching to child indexes, but per a recent report from Claus Stadler, constraint exclusion of UNION ALL subqueries was still broken, because constant-simplification didn't handle the injected PlaceHolderVars well either. On reflection, the original patch was quite misguided: there is no reason to expect that EquivalenceClass child members will be distinct. So instead of trying to make them so, we should ensure that we can cope with the situation when they're not. Accordingly, this patch reverts the code changes in the above-mentioned commits (though the regression test cases they added stay). Instead, I've added assorted defenses to make sure that duplicate EC child members don't cause any problems. Teodor's original problem ("MergeAppend child's targetlist doesn't match MergeAppend") is addressed more directly by revising prepare_sort_from_pathkeys to let the parent MergeAppend's sort list guide creation of each child's sort list. In passing, get rid of add_sort_column; as far as I can tell, testing for duplicate sort keys at this stage is dead code. Certainly it doesn't trigger often enough to be worth expending cycles on in ordinary queries. And keeping the test would've greatly complicated the new logic in prepare_sort_from_pathkeys, because comparing pathkey list entries against a previous output array requires that we not skip any entries in the list. Back-patch to 9.1, like the previous patches. The only known issue in this area that wasn't caused by the ill-advised previous patches was the MergeAppend planning failure, which of course is not relevant before 9.1. It's possible that we need some of the new defenses against duplicate child EC entries in older branches, but until there's some clear evidence of that I'm going to refrain from back-patching further.
2012-03-16 18:11:12 +01:00
* trouble.) However, the single table could be buried in several levels
* of FromExpr due to subqueries. Note the "single" table could be an
* inheritance parent, too, including the case of a UNION ALL subquery
* that's been flattened to an appendrel.
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
*/
Fix a performance regression in 8.2: optimization of MIN/MAX into indexscans had stopped working for tables buried inside views or sub-selects. This is because I had gotten rid of the simplify_jointree() preprocessing step, and optimize_minmax_aggregates() wasn't smart enough to deal with a non-canonical FromExpr. Per gripe from Bill Howe.
2007-02-06 07:50:26 +01:00
jtnode = parse->jointree;
while (IsA(jtnode, FromExpr))
{
if (list_length(jtnode->fromlist) != 1)
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
return;
Fix a performance regression in 8.2: optimization of MIN/MAX into indexscans had stopped working for tables buried inside views or sub-selects. This is because I had gotten rid of the simplify_jointree() preprocessing step, and optimize_minmax_aggregates() wasn't smart enough to deal with a non-canonical FromExpr. Per gripe from Bill Howe.
2007-02-06 07:50:26 +01:00
jtnode = linitial(jtnode->fromlist);
}
if (!IsA(jtnode, RangeTblRef))
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
return;
Fix a performance regression in 8.2: optimization of MIN/MAX into indexscans had stopped working for tables buried inside views or sub-selects. This is because I had gotten rid of the simplify_jointree() preprocessing step, and optimize_minmax_aggregates() wasn't smart enough to deal with a non-canonical FromExpr. Per gripe from Bill Howe.
2007-02-06 07:50:26 +01:00
rtr = (RangeTblRef *) jtnode;
Some further performance tweaks for planning large inheritance trees that are mostly excluded by constraints: do the CE test a bit earlier to save some adjust_appendrel_attrs() work on excluded children, and arrange to use array indexing rather than rt_fetch() to fetch RTEs in the main body of the planner. The latter is something I'd wanted to do for awhile anyway, but seeing list_nth_cell() as 35% of the runtime gets one's attention.
2007-04-21 23:01:45 +02:00
rte = planner_rt_fetch(rtr->rtindex, root);
Revisit handling of UNION ALL subqueries with non-Var output columns. In commit 57664ed25e5dea117158a2e663c29e60b3546e1c I tried to fix a bug reported by Teodor Sigaev by making non-simple-Var output columns distinct (by wrapping their expressions with dummy PlaceHolderVar nodes). This did not work too well. Commit b28ffd0fcc583c1811e5295279e7d4366c3cae6c fixed some ensuing problems with matching to child indexes, but per a recent report from Claus Stadler, constraint exclusion of UNION ALL subqueries was still broken, because constant-simplification didn't handle the injected PlaceHolderVars well either. On reflection, the original patch was quite misguided: there is no reason to expect that EquivalenceClass child members will be distinct. So instead of trying to make them so, we should ensure that we can cope with the situation when they're not. Accordingly, this patch reverts the code changes in the above-mentioned commits (though the regression test cases they added stay). Instead, I've added assorted defenses to make sure that duplicate EC child members don't cause any problems. Teodor's original problem ("MergeAppend child's targetlist doesn't match MergeAppend") is addressed more directly by revising prepare_sort_from_pathkeys to let the parent MergeAppend's sort list guide creation of each child's sort list. In passing, get rid of add_sort_column; as far as I can tell, testing for duplicate sort keys at this stage is dead code. Certainly it doesn't trigger often enough to be worth expending cycles on in ordinary queries. And keeping the test would've greatly complicated the new logic in prepare_sort_from_pathkeys, because comparing pathkey list entries against a previous output array requires that we not skip any entries in the list. Back-patch to 9.1, like the previous patches. The only known issue in this area that wasn't caused by the ill-advised previous patches was the MergeAppend planning failure, which of course is not relevant before 9.1. It's possible that we need some of the new defenses against duplicate child EC entries in older branches, but until there's some clear evidence of that I'm going to refrain from back-patching further.
2012-03-16 18:11:12 +01:00
if (rte->rtekind == RTE_RELATION)
Run pgindent on 9.2 source tree in preparation for first 9.3 commit-fest.
2012-06-10 21:20:04 +02:00
/* ordinary relation, ok */ ;
Revisit handling of UNION ALL subqueries with non-Var output columns. In commit 57664ed25e5dea117158a2e663c29e60b3546e1c I tried to fix a bug reported by Teodor Sigaev by making non-simple-Var output columns distinct (by wrapping their expressions with dummy PlaceHolderVar nodes). This did not work too well. Commit b28ffd0fcc583c1811e5295279e7d4366c3cae6c fixed some ensuing problems with matching to child indexes, but per a recent report from Claus Stadler, constraint exclusion of UNION ALL subqueries was still broken, because constant-simplification didn't handle the injected PlaceHolderVars well either. On reflection, the original patch was quite misguided: there is no reason to expect that EquivalenceClass child members will be distinct. So instead of trying to make them so, we should ensure that we can cope with the situation when they're not. Accordingly, this patch reverts the code changes in the above-mentioned commits (though the regression test cases they added stay). Instead, I've added assorted defenses to make sure that duplicate EC child members don't cause any problems. Teodor's original problem ("MergeAppend child's targetlist doesn't match MergeAppend") is addressed more directly by revising prepare_sort_from_pathkeys to let the parent MergeAppend's sort list guide creation of each child's sort list. In passing, get rid of add_sort_column; as far as I can tell, testing for duplicate sort keys at this stage is dead code. Certainly it doesn't trigger often enough to be worth expending cycles on in ordinary queries. And keeping the test would've greatly complicated the new logic in prepare_sort_from_pathkeys, because comparing pathkey list entries against a previous output array requires that we not skip any entries in the list. Back-patch to 9.1, like the previous patches. The only known issue in this area that wasn't caused by the ill-advised previous patches was the MergeAppend planning failure, which of course is not relevant before 9.1. It's possible that we need some of the new defenses against duplicate child EC entries in older branches, but until there's some clear evidence of that I'm going to refrain from back-patching further.
2012-03-16 18:11:12 +01:00
else if (rte->rtekind == RTE_SUBQUERY && rte->inh)
Run pgindent on 9.2 source tree in preparation for first 9.3 commit-fest.
2012-06-10 21:20:04 +02:00
/* flattened UNION ALL subquery, ok */ ;
Revisit handling of UNION ALL subqueries with non-Var output columns. In commit 57664ed25e5dea117158a2e663c29e60b3546e1c I tried to fix a bug reported by Teodor Sigaev by making non-simple-Var output columns distinct (by wrapping their expressions with dummy PlaceHolderVar nodes). This did not work too well. Commit b28ffd0fcc583c1811e5295279e7d4366c3cae6c fixed some ensuing problems with matching to child indexes, but per a recent report from Claus Stadler, constraint exclusion of UNION ALL subqueries was still broken, because constant-simplification didn't handle the injected PlaceHolderVars well either. On reflection, the original patch was quite misguided: there is no reason to expect that EquivalenceClass child members will be distinct. So instead of trying to make them so, we should ensure that we can cope with the situation when they're not. Accordingly, this patch reverts the code changes in the above-mentioned commits (though the regression test cases they added stay). Instead, I've added assorted defenses to make sure that duplicate EC child members don't cause any problems. Teodor's original problem ("MergeAppend child's targetlist doesn't match MergeAppend") is addressed more directly by revising prepare_sort_from_pathkeys to let the parent MergeAppend's sort list guide creation of each child's sort list. In passing, get rid of add_sort_column; as far as I can tell, testing for duplicate sort keys at this stage is dead code. Certainly it doesn't trigger often enough to be worth expending cycles on in ordinary queries. And keeping the test would've greatly complicated the new logic in prepare_sort_from_pathkeys, because comparing pathkey list entries against a previous output array requires that we not skip any entries in the list. Back-patch to 9.1, like the previous patches. The only known issue in this area that wasn't caused by the ill-advised previous patches was the MergeAppend planning failure, which of course is not relevant before 9.1. It's possible that we need some of the new defenses against duplicate child EC entries in older branches, but until there's some clear evidence of that I'm going to refrain from back-patching further.
2012-03-16 18:11:12 +01:00
else
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
return;
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
/*
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
* Scan the tlist and HAVING qual to find all the aggregates and verify
pgindent run for 9.4 This includes removing tabs after periods in C comments, which was applied to back branches, so this change should not effect backpatching.
2014-05-06 18:12:18 +02:00
* all are MIN/MAX aggregates. Stop as soon as we find one that isn't.
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
*/
aggs_list = NIL;
if (find_minmax_aggs_walker((Node *) tlist, &aggs_list))
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
return;
Remove planner's private fields from Query struct, and put them into a new PlannerInfo struct, which is passed around instead of the bare Query in all the planning code. This commit is essentially just a code-beautification exercise, but it does open the door to making larger changes to the planner data structures without having to muck with the widely-known Query struct.
2005-06-06 00:32:58 +02:00
if (find_minmax_aggs_walker(parse->havingQual, &aggs_list))
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
return;
/*
* OK, there is at least the possibility of performing the optimization.
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
* Build an access path for each aggregate. If any of the aggregates
* prove to be non-indexable, give up; there is no point in optimizing
* just some of them.
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
*/
foreach(lc, aggs_list)
{
MinMaxAggInfo *mminfo = (MinMaxAggInfo *) lfirst(lc);
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
Oid eqop;
bool reverse;
/*
* We'll need the equality operator that goes with the aggregate's
* ordering operator.
*/
eqop = get_equality_op_for_ordering_op(mminfo->aggsortop, &reverse);
pgindent run before PG 9.1 beta 1.
2011-04-10 17:42:00 +02:00
if (!OidIsValid(eqop)) /* shouldn't happen */
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
elog(ERROR, "could not find equality operator for ordering operator %u",
mminfo->aggsortop);
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
/*
* We can use either an ordering that gives NULLS FIRST or one that
* gives NULLS LAST; furthermore there's unlikely to be much
* performance difference between them, so it doesn't seem worth
pgindent run for 9.4 This includes removing tabs after periods in C comments, which was applied to back branches, so this change should not effect backpatching.
2014-05-06 18:12:18 +02:00
* costing out both ways if we get a hit on the first one. NULLS
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
* FIRST is more likely to be available if the operator is a
* reverse-sort operator, so try that first if reverse.
*/
if (build_minmax_path(root, mminfo, eqop, mminfo->aggsortop, reverse))
continue;
if (build_minmax_path(root, mminfo, eqop, mminfo->aggsortop, !reverse))
continue;
/* No indexable path for this aggregate, so fail */
return;
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
}
/*
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
* OK, we can do the query this way. Prepare to create a MinMaxAggPath
* node.
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
*
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
* First, create an output Param node for each agg. (If we end up not
* using the MinMaxAggPath, we'll waste a PARAM_EXEC slot for each agg,
* which is not worth worrying about. We can't wait till create_plan time
* to decide whether to make the Param, unfortunately.)
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
*/
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
foreach(lc, aggs_list)
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
{
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
MinMaxAggInfo *mminfo = (MinMaxAggInfo *) lfirst(lc);
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
mminfo->param =
SS_make_initplan_output_param(root,
exprType((Node *) mminfo->target),
-1,
Phase 3 of pgindent updates. Don't move parenthesized lines to the left, even if that means they flow past the right margin. By default, BSD indent lines up statement continuation lines that are within parentheses so that they start just to the right of the preceding left parenthesis. However, traditionally, if that resulted in the continuation line extending to the right of the desired right margin, then indent would push it left just far enough to not overrun the margin, if it could do so without making the continuation line start to the left of the current statement indent. That makes for a weird mix of indentations unless one has been completely rigid about never violating the 80-column limit. This behavior has been pretty universally panned by Postgres developers. Hence, disable it with indent's new -lpl switch, so that parenthesized lines are always lined up with the preceding left paren. This patch is much less interesting than the first round of indent changes, but also bulkier, so I thought it best to separate the effects. Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
2017-06-21 21:35:54 +02:00
exprCollation((Node *) mminfo->target));
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
}
/*
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
* Create a MinMaxAggPath node with the appropriate estimated costs and
* other needed data, and add it to the UPPERREL_GROUP_AGG upperrel, where
* it will compete against the standard aggregate implementation. (It
* will likely always win, but we need not assume that here.)
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
*
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
* Note: grouping_planner won't have created this upperrel yet, but it's
Rethink the GetForeignUpperPaths API (again). In the previous design, the GetForeignUpperPaths FDW callback hook was called before we got around to labeling upper relations with the proper consider_parallel flag; this meant that any upper paths created by an FDW would be marked not-parallel-safe. While that's probably just as well right now, we aren't going to want it to be true forever. Hence, abandon the idea that FDWs should be allowed to inject upper paths before the core code has gotten around to creating the relevant upper relation. (Well, actually they still can, but it's on their own heads how well it works.) Instead, adopt the same API already designed for create_upper_paths_hook: we call GetForeignUpperPaths after each upperrel has been created and populated with the paths the core planner knows how to make.
2016-07-01 19:12:34 +02:00
* fine for us to create it first. We will not have inserted the correct
* consider_parallel value in it, but MinMaxAggPath paths are currently
* never parallel-safe anyway, so that doesn't matter. Likewise, it
* doesn't matter that we haven't filled FDW-related fields in the rel.
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
*/
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
grouped_rel = fetch_upper_rel(root, UPPERREL_GROUP_AGG, NULL);
add_path(grouped_rel, (Path *)
create_minmaxagg_path(root, grouped_rel,
create_pathtarget(root, tlist),
aggs_list,
(List *) parse->havingQual));
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
}
/*
* find_minmax_aggs_walker
* Recursively scan the Aggref nodes in an expression tree, and check
* that each one is a MIN/MAX aggregate. If so, build a list of the
* distinct aggregate calls in the tree.
*
* Returns TRUE if a non-MIN/MAX aggregate is found, FALSE otherwise.
* (This seemingly-backward definition is used because expression_tree_walker
* aborts the scan on TRUE return, which is what we want.)
*
* Found aggregates are added to the list at *context; it's up to the caller
* to initialize the list to NIL.
*
* This does not descend into subqueries, and so should be used only after
* reduction of sublinks to subplans. There mustn't be outer-aggregate
* references either.
*/
static bool
find_minmax_aggs_walker(Node *node, List **context)
{
if (node == NULL)
return false;
if (IsA(node, Aggref))
{
Aggref *aggref = (Aggref *) node;
Oid aggsortop;
Support ORDER BY within aggregate function calls, at long last providing a non-kluge method for controlling the order in which values are fed to an aggregate function. At the same time eliminate the old implementation restriction that DISTINCT was only supported for single-argument aggregates. Possibly release-notable behavioral change: formerly, agg(DISTINCT x) dropped null values of x unconditionally. Now, it does so only if the agg transition function is strict; otherwise nulls are treated as DISTINCT normally would, ie, you get one copy. Andrew Gierth, reviewed by Hitoshi Harada
2009-12-15 18:57:48 +01:00
TargetEntry *curTarget;
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
MinMaxAggInfo *mminfo;
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
ListCell *l;
Assert(aggref->agglevelsup == 0);
Comment on why planagg.c punts "MIN(x ORDER BY y)".
2013-07-17 02:14:37 +02:00
if (list_length(aggref->args) != 1)
Aggregate functions now support multiple input arguments. I also took the opportunity to treat COUNT(*) as a zero-argument aggregate instead of the old hack that equated it to COUNT(1); this is materially cleaner (no more weird ANYOID cases) and ought to be at least a tiny bit faster. Original patch by Sergey Koposov; review, documentation, simple regression tests, pg_dump and psql support by moi.
2006-07-27 21:52:07 +02:00
return true; /* it couldn't be MIN/MAX */
Simplify query_planner's API by having it return the top-level RelOptInfo. Formerly, query_planner returned one or possibly two Paths for the topmost join relation, so that grouping_planner didn't see the join RelOptInfo (at least not directly; it didn't have any hesitation about examining cheapest_path->parent, though). However, correct selection of the Paths involved a significant amount of coupling between query_planner and grouping_planner, a problem which has gotten worse over time. It seems best to give up on this API choice and instead return the topmost RelOptInfo explicitly. Then grouping_planner can pull out the Paths it wants from the rel's path list. In this way we can remove all knowledge of grouping behaviors from query_planner. The only real benefit of the old way is that in the case of an empty FROM clause, we never made any RelOptInfos at all, just a Path. Now we have to gin up a dummy RelOptInfo to represent the empty FROM clause. That's not a very big deal though. While at it, simplify query_planner's API a bit more by having the caller set up root->tuple_fraction and root->limit_tuples, rather than passing those values as separate parameters. Since query_planner no longer does anything with either value, requiring it to fill the PlannerInfo fields seemed pretty arbitrary. This patch just rearranges code; it doesn't (intentionally) change any behaviors. Followup patches will do more interesting things.
2013-08-05 21:00:57 +02:00
Comment on why planagg.c punts "MIN(x ORDER BY y)".
2013-07-17 02:14:37 +02:00
/*
* ORDER BY is usually irrelevant for MIN/MAX, but it can change the
* outcome if the aggsortop's operator class recognizes non-identical
* values as equal. For example, 4.0 and 4.00 are equal according to
* numeric_ops, yet distinguishable. If MIN() receives more than one
* value equal to 4.0 and no value less than 4.0, it is unspecified
* which of those equal values MIN() returns. An ORDER BY expression
* that differs for each of those equal values of the argument
* expression makes the result predictable once again. This is a
* niche requirement, and we do not implement it with subquery paths.
Support ordered-set (WITHIN GROUP) aggregates. This patch introduces generic support for ordered-set and hypothetical-set aggregate functions, as well as implementations of the instances defined in SQL:2008 (percentile_cont(), percentile_disc(), rank(), dense_rank(), percent_rank(), cume_dist()). We also added mode() though it is not in the spec, as well as versions of percentile_cont() and percentile_disc() that can compute multiple percentile values in one pass over the data. Unlike the original submission, this patch puts full control of the sorting process in the hands of the aggregate's support functions. To allow the support functions to find out how they're supposed to sort, a new API function AggGetAggref() is added to nodeAgg.c. This allows retrieval of the aggregate call's Aggref node, which may have other uses beyond the immediate need. There is also support for ordered-set aggregates to install cleanup callback functions, so that they can be sure that infrastructure such as tuplesort objects gets cleaned up. In passing, make some fixes in the recently-added support for variadic aggregates, and make some editorial adjustments in the recent FILTER additions for aggregates. Also, simplify use of IsBinaryCoercible() by allowing it to succeed whenever the target type is ANY or ANYELEMENT. It was inconsistent that it dealt with other polymorphic target types but not these. Atri Sharma and Andrew Gierth; reviewed by Pavel Stehule and Vik Fearing, and rather heavily editorialized upon by Tom Lane
2013-12-23 22:11:35 +01:00
* In any case, this test lets us reject ordered-set aggregates
* quickly.
Comment on why planagg.c punts "MIN(x ORDER BY y)".
2013-07-17 02:14:37 +02:00
*/
if (aggref->aggorder != NIL)
return true;
Support ordered-set (WITHIN GROUP) aggregates. This patch introduces generic support for ordered-set and hypothetical-set aggregate functions, as well as implementations of the instances defined in SQL:2008 (percentile_cont(), percentile_disc(), rank(), dense_rank(), percent_rank(), cume_dist()). We also added mode() though it is not in the spec, as well as versions of percentile_cont() and percentile_disc() that can compute multiple percentile values in one pass over the data. Unlike the original submission, this patch puts full control of the sorting process in the hands of the aggregate's support functions. To allow the support functions to find out how they're supposed to sort, a new API function AggGetAggref() is added to nodeAgg.c. This allows retrieval of the aggregate call's Aggref node, which may have other uses beyond the immediate need. There is also support for ordered-set aggregates to install cleanup callback functions, so that they can be sure that infrastructure such as tuplesort objects gets cleaned up. In passing, make some fixes in the recently-added support for variadic aggregates, and make some editorial adjustments in the recent FILTER additions for aggregates. Also, simplify use of IsBinaryCoercible() by allowing it to succeed whenever the target type is ANY or ANYELEMENT. It was inconsistent that it dealt with other polymorphic target types but not these. Atri Sharma and Andrew Gierth; reviewed by Pavel Stehule and Vik Fearing, and rather heavily editorialized upon by Tom Lane
2013-12-23 22:11:35 +01:00
/* note: we do not care if DISTINCT is mentioned ... */
Simplify query_planner's API by having it return the top-level RelOptInfo. Formerly, query_planner returned one or possibly two Paths for the topmost join relation, so that grouping_planner didn't see the join RelOptInfo (at least not directly; it didn't have any hesitation about examining cheapest_path->parent, though). However, correct selection of the Paths involved a significant amount of coupling between query_planner and grouping_planner, a problem which has gotten worse over time. It seems best to give up on this API choice and instead return the topmost RelOptInfo explicitly. Then grouping_planner can pull out the Paths it wants from the rel's path list. In this way we can remove all knowledge of grouping behaviors from query_planner. The only real benefit of the old way is that in the case of an empty FROM clause, we never made any RelOptInfos at all, just a Path. Now we have to gin up a dummy RelOptInfo to represent the empty FROM clause. That's not a very big deal though. While at it, simplify query_planner's API a bit more by having the caller set up root->tuple_fraction and root->limit_tuples, rather than passing those values as separate parameters. Since query_planner no longer does anything with either value, requiring it to fill the PlannerInfo fields seemed pretty arbitrary. This patch just rearranges code; it doesn't (intentionally) change any behaviors. Followup patches will do more interesting things.
2013-08-05 21:00:57 +02:00
Implement the FILTER clause for aggregate function calls. This is SQL-standard with a few extensions, namely support for subqueries and outer references in clause expressions. catversion bump due to change in Aggref and WindowFunc. David Fetter, reviewed by Dean Rasheed.
2013-07-17 02:15:36 +02:00
/*
* We might implement the optimization when a FILTER clause is present
Support ordered-set (WITHIN GROUP) aggregates. This patch introduces generic support for ordered-set and hypothetical-set aggregate functions, as well as implementations of the instances defined in SQL:2008 (percentile_cont(), percentile_disc(), rank(), dense_rank(), percent_rank(), cume_dist()). We also added mode() though it is not in the spec, as well as versions of percentile_cont() and percentile_disc() that can compute multiple percentile values in one pass over the data. Unlike the original submission, this patch puts full control of the sorting process in the hands of the aggregate's support functions. To allow the support functions to find out how they're supposed to sort, a new API function AggGetAggref() is added to nodeAgg.c. This allows retrieval of the aggregate call's Aggref node, which may have other uses beyond the immediate need. There is also support for ordered-set aggregates to install cleanup callback functions, so that they can be sure that infrastructure such as tuplesort objects gets cleaned up. In passing, make some fixes in the recently-added support for variadic aggregates, and make some editorial adjustments in the recent FILTER additions for aggregates. Also, simplify use of IsBinaryCoercible() by allowing it to succeed whenever the target type is ANY or ANYELEMENT. It was inconsistent that it dealt with other polymorphic target types but not these. Atri Sharma and Andrew Gierth; reviewed by Pavel Stehule and Vik Fearing, and rather heavily editorialized upon by Tom Lane
2013-12-23 22:11:35 +01:00
* by adding the filter to the quals of the generated subquery. For
* now, just punt.
Implement the FILTER clause for aggregate function calls. This is SQL-standard with a few extensions, namely support for subqueries and outer references in clause expressions. catversion bump due to change in Aggref and WindowFunc. David Fetter, reviewed by Dean Rasheed.
2013-07-17 02:15:36 +02:00
*/
if (aggref->aggfilter != NULL)
return true;
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
aggsortop = fetch_agg_sort_op(aggref->aggfnoid);
if (!OidIsValid(aggsortop))
return true; /* not a MIN/MAX aggregate */
Comment on why planagg.c punts "MIN(x ORDER BY y)".
2013-07-17 02:14:37 +02:00
curTarget = (TargetEntry *) linitial(aggref->args);
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
if (contain_mutable_functions((Node *) curTarget->expr))
return true; /* not potentially indexable */
if (type_is_rowtype(exprType((Node *) curTarget->expr)))
return true; /* IS NOT NULL would have weird semantics */
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
/*
* Check whether it's already in the list, and add it if not.
*/
foreach(l, *context)
{
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
mminfo = (MinMaxAggInfo *) lfirst(l);
if (mminfo->aggfnoid == aggref->aggfnoid &&
equal(mminfo->target, curTarget->expr))
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
return false;
}
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
mminfo = makeNode(MinMaxAggInfo);
mminfo->aggfnoid = aggref->aggfnoid;
mminfo->aggsortop = aggsortop;
mminfo->target = curTarget->expr;
pgindent run before PG 9.1 beta 1.
2011-04-10 17:42:00 +02:00
mminfo->subroot = NULL; /* don't compute path yet */
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
mminfo->path = NULL;
mminfo->pathcost = 0;
mminfo->param = NULL;
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
*context = lappend(*context, mminfo);
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
/*
Standard pgindent run for 8.1.
2005-10-15 04:49:52 +02:00
* We need not recurse into the argument, since it can't contain any
* aggregates.
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
*/
return false;
}
Assert(!IsA(node, SubLink));
return expression_tree_walker(node, find_minmax_aggs_walker,
(void *) context);
}
/*
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
* build_minmax_path
* Given a MIN/MAX aggregate, try to build an indexscan Path it can be
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
* optimized with.
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
*
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
* If successful, stash the best path in *mminfo and return TRUE.
* Otherwise, return FALSE.
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
*/
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
static bool
build_minmax_path(PlannerInfo *root, MinMaxAggInfo *mminfo,
Oid eqop, Oid sortop, bool nulls_first)
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
{
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
PlannerInfo *subroot;
Query *parse;
TargetEntry *tle;
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
List *tlist;
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
NullTest *ntest;
SortGroupClause *sortcl;
Simplify query_planner's API by having it return the top-level RelOptInfo. Formerly, query_planner returned one or possibly two Paths for the topmost join relation, so that grouping_planner didn't see the join RelOptInfo (at least not directly; it didn't have any hesitation about examining cheapest_path->parent, though). However, correct selection of the Paths involved a significant amount of coupling between query_planner and grouping_planner, a problem which has gotten worse over time. It seems best to give up on this API choice and instead return the topmost RelOptInfo explicitly. Then grouping_planner can pull out the Paths it wants from the rel's path list. In this way we can remove all knowledge of grouping behaviors from query_planner. The only real benefit of the old way is that in the case of an empty FROM clause, we never made any RelOptInfos at all, just a Path. Now we have to gin up a dummy RelOptInfo to represent the empty FROM clause. That's not a very big deal though. While at it, simplify query_planner's API a bit more by having the caller set up root->tuple_fraction and root->limit_tuples, rather than passing those values as separate parameters. Since query_planner no longer does anything with either value, requiring it to fill the PlannerInfo fields seemed pretty arbitrary. This patch just rearranges code; it doesn't (intentionally) change any behaviors. Followup patches will do more interesting things.
2013-08-05 21:00:57 +02:00
RelOptInfo *final_rel;
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
Path *sorted_path;
Cost path_cost;
Reimplement planner's handling of MIN/MAX aggregate optimization. Per my recent proposal, get rid of all the direct inspection of indexes and manual generation of paths in planagg.c. Instead, set up EquivalenceClasses for the aggregate argument expressions, and let the regular path generation logic deal with creating paths that can satisfy those sort orders. This makes planagg.c a bit more visible to the rest of the planner than it was originally, but the approach is basically a lot cleaner than before. A major advantage of doing it this way is that we get MIN/MAX optimization on inheritance trees (using MergeAppend of indexscans) practically for free, whereas in the old way we'd have had to add a whole lot more duplicative logic. One small disadvantage of this approach is that MIN/MAX aggregates can no longer exploit partial indexes having an "x IS NOT NULL" predicate, unless that restriction or something that implies it is specified in the query. The previous implementation was able to use the added "x IS NOT NULL" condition as an extra predicate proof condition, but in this version we rely entirely on indexes that are considered usable by the main planning process. That seems a fair tradeoff for the simplicity and functionality gained.
2010-11-04 17:01:17 +01:00
double path_fraction;
Teach planagg.c that partial indexes specifying WHERE foo IS NOT NULL can be used to perform MIN(foo) or MAX(foo), since we want to discard null rows in the indexscan anyway. (This would probably fall out for free if we were injecting the IS NOT NULL clause somewhere earlier, but given the current anatomy of the MIN/MAX optimization code we have to do it explicitly. Fortunately, very little added code is needed.) Per a discussion with Henk de Wit.
2007-10-13 02:58:03 +02:00
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
/*
* We are going to construct what is effectively a sub-SELECT query, so
* clone the current query level's state and adjust it to make it look
* like a subquery. Any outer references will now be one level higher
* than before. (This means that when we are done, there will be no Vars
* of level 1, which is why the subquery can become an initplan.)
Teach planagg.c that partial indexes specifying WHERE foo IS NOT NULL can be used to perform MIN(foo) or MAX(foo), since we want to discard null rows in the indexscan anyway. (This would probably fall out for free if we were injecting the IS NOT NULL clause somewhere earlier, but given the current anatomy of the MIN/MAX optimization code we have to do it explicitly. Fortunately, very little added code is needed.) Per a discussion with Henk de Wit.
2007-10-13 02:58:03 +02:00
*/
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
subroot = (PlannerInfo *) palloc(sizeof(PlannerInfo));
memcpy(subroot, root, sizeof(PlannerInfo));
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
subroot->query_level++;
subroot->parent_root = root;
Postpone extParam/allParam calculations until the very end of planning. Until now we computed these Param ID sets at the end of subquery_planner, but that approach depends on subquery_planner returning a concrete Plan tree. We would like to switch over to returning one or more Paths for a subquery, and in that representation the necessary details aren't fully fleshed out (not to mention that we don't really want to do this work for Paths that end up getting discarded). Hence, refactor so that we can compute the param ID sets at the end of planning, just before set_plan_references is run. The main change necessary to make this work is that we need to capture the set of outer-level Param IDs available to the current query level before exiting subquery_planner, since the outer levels' plan_params lists are transient. (That's not going to pose a problem for returning Paths, since all the work involved in producing that data is part of expression preprocessing, which will continue to happen before Paths are produced.) On the plus side, this change gets rid of several existing kluges. Eventually I'd like to get rid of SS_finalize_plan altogether in favor of doing this work during set_plan_references, but that will require some complex rejiggering because SS_finalize_plan needs to visit subplans and initplans before the main plan. So leave that idea for another day.
2015-08-12 05:48:37 +02:00
/* reset subplan-related stuff */
subroot->plan_params = NIL;
subroot->outer_params = NULL;
subroot->init_plans = NIL;
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
Cast result of copyObject() to correct type copyObject() is declared to return void *, which allows easily assigning the result independent of the input, but it loses all type checking. If the compiler supports typeof or something similar, cast the result to the input type. This creates a greater amount of type safety. In some cases, where the result is assigned to a generic type such as Node * or Expr *, new casts are now necessary, but in general casts are now unnecessary in the normal case and indicate that something unusual is happening. Reviewed-by: Mark Dilger <hornschnorter@gmail.com>
2017-03-09 21:18:59 +01:00
subroot->parse = parse = copyObject(root->parse);
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
IncrementVarSublevelsUp((Node *) parse, 1, 1);
/* append_rel_list might contain outer Vars? */
Cast result of copyObject() to correct type copyObject() is declared to return void *, which allows easily assigning the result independent of the input, but it loses all type checking. If the compiler supports typeof or something similar, cast the result to the input type. This creates a greater amount of type safety. In some cases, where the result is assigned to a generic type such as Node * or Expr *, new casts are now necessary, but in general casts are now unnecessary in the normal case and indicate that something unusual is happening. Reviewed-by: Mark Dilger <hornschnorter@gmail.com>
2017-03-09 21:18:59 +01:00
subroot->append_rel_list = copyObject(root->append_rel_list);
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
IncrementVarSublevelsUp((Node *) subroot->append_rel_list, 1, 1);
Get rid of the planner's LateralJoinInfo data structure. I originally modeled this data structure on SpecialJoinInfo, but after commit acfcd45cacb6df23 that looks like a pretty poor decision. All we really need is relid sets identifying laterally-referenced rels; and most of the time, what we want to know about includes indirect lateral references, a case the LateralJoinInfo data was unsuited to compute with any efficiency. The previous commit redefined RelOptInfo.lateral_relids as the transitive closure of lateral references, so that it easily supports checking indirect references. For the places where we really do want just direct references, add a new RelOptInfo field direct_lateral_relids, which is easily set up as a copy of lateral_relids before we perform the transitive closure calculation. Then we can just drop lateral_info_list and LateralJoinInfo and the supporting code. This makes the planner's handling of lateral references noticeably more efficient, and shorter too. Such a change can't be back-patched into stable branches for fear of breaking extensions that might be looking at the planner's data structures; but it seems not too late to push it into 9.5, so I've done so.
2015-12-11 21:52:16 +01:00
/* There shouldn't be any OJ info to translate, as yet */
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
Assert(subroot->join_info_list == NIL);
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
/* and we haven't made equivalence classes, either */
Assert(subroot->eq_classes == NIL);
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
/* and we haven't created PlaceHolderInfos, either */
Assert(subroot->placeholder_list == NIL);
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
/*----------
* Generate modified query of the form
* (SELECT col FROM tab
* WHERE col IS NOT NULL AND existing-quals
* ORDER BY col ASC/DESC
* LIMIT 1)
*----------
*/
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
/* single tlist entry that is the aggregate target */
tle = makeTargetEntry(copyObject(mminfo->target),
(AttrNumber) 1,
pstrdup("agg_target"),
false);
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
tlist = list_make1(tle);
subroot->processed_tlist = parse->targetList = tlist;
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
/* No HAVING, no DISTINCT, no aggregates anymore */
parse->havingQual = NULL;
subroot->hasHavingQual = false;
parse->distinctClause = NIL;
parse->hasDistinctOn = false;
parse->hasAggs = false;
/* Build "target IS NOT NULL" expression */
ntest = makeNode(NullTest);
ntest->nulltesttype = IS_NOT_NULL;
ntest->arg = copyObject(mminfo->target);
/* we checked it wasn't a rowtype in find_minmax_aggs_walker */
ntest->argisrow = false;
Add parse location fields to NullTest and BooleanTest structs. We did not need a location tag on NullTest or BooleanTest before, because no error messages referred directly to their locations. That's planned to change though, so add these fields in a separate housekeeping commit. Catversion bump because stored rules may change.
2015-02-22 20:40:27 +01:00
ntest->location = -1;
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
/* User might have had that in WHERE already */
if (!list_member((List *) parse->jointree->quals, ntest))
parse->jointree->quals = (Node *)
lcons(ntest, (List *) parse->jointree->quals);
/* Build suitable ORDER BY clause */
sortcl = makeNode(SortGroupClause);
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
sortcl->tleSortGroupRef = assignSortGroupRef(tle, tlist);
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
sortcl->eqop = eqop;
sortcl->sortop = sortop;
sortcl->nulls_first = nulls_first;
pgindent run before PG 9.1 beta 1.
2011-04-10 17:42:00 +02:00
sortcl->hashable = false; /* no need to make this accurate */
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
parse->sortClause = list_make1(sortcl);
/* set up expressions for LIMIT 1 */
parse->limitOffset = NULL;
Pass collation to makeConst() instead of looking it up internally. In nearly all cases, the caller already knows the correct collation, and in a number of places, the value the caller has handy is more correct than the default for the type would be. (In particular, this patch makes it significantly less likely that eval_const_expressions will result in changing the exposed collation of an expression.) So an internal lookup is both expensive and wrong.
2011-03-26 01:10:42 +01:00
parse->limitCount = (Node *) makeConst(INT8OID, -1, InvalidOid,
sizeof(int64),
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
Int64GetDatum(1), false,
FLOAT8PASSBYVAL);
Teach planagg.c that partial indexes specifying WHERE foo IS NOT NULL can be used to perform MIN(foo) or MAX(foo), since we want to discard null rows in the indexscan anyway. (This would probably fall out for free if we were injecting the IS NOT NULL clause somewhere earlier, but given the current anatomy of the MIN/MAX optimization code we have to do it explicitly. Fortunately, very little added code is needed.) Per a discussion with Henk de Wit.
2007-10-13 02:58:03 +02:00
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
/*
pgindent run before PG 9.1 beta 1.
2011-04-10 17:42:00 +02:00
* Generate the best paths for this query, telling query_planner that we
* have LIMIT 1.
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
*/
Simplify query_planner's API by having it return the top-level RelOptInfo. Formerly, query_planner returned one or possibly two Paths for the topmost join relation, so that grouping_planner didn't see the join RelOptInfo (at least not directly; it didn't have any hesitation about examining cheapest_path->parent, though). However, correct selection of the Paths involved a significant amount of coupling between query_planner and grouping_planner, a problem which has gotten worse over time. It seems best to give up on this API choice and instead return the topmost RelOptInfo explicitly. Then grouping_planner can pull out the Paths it wants from the rel's path list. In this way we can remove all knowledge of grouping behaviors from query_planner. The only real benefit of the old way is that in the case of an empty FROM clause, we never made any RelOptInfos at all, just a Path. Now we have to gin up a dummy RelOptInfo to represent the empty FROM clause. That's not a very big deal though. While at it, simplify query_planner's API a bit more by having the caller set up root->tuple_fraction and root->limit_tuples, rather than passing those values as separate parameters. Since query_planner no longer does anything with either value, requiring it to fill the PlannerInfo fields seemed pretty arbitrary. This patch just rearranges code; it doesn't (intentionally) change any behaviors. Followup patches will do more interesting things.
2013-08-05 21:00:57 +02:00
subroot->tuple_fraction = 1.0;
subroot->limit_tuples = 1.0;
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
final_rel = query_planner(subroot, tlist, minmax_qp_callback, NULL);
/*
* Since we didn't go through subquery_planner() to handle the subquery,
* we have to do some of the same cleanup it would do, in particular cope
* with params and initplans used within this subquery. (This won't
* matter if we end up not using the subplan.)
*/
SS_identify_outer_params(subroot);
SS_charge_for_initplans(subroot, final_rel);
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
/*
Simplify query_planner's API by having it return the top-level RelOptInfo. Formerly, query_planner returned one or possibly two Paths for the topmost join relation, so that grouping_planner didn't see the join RelOptInfo (at least not directly; it didn't have any hesitation about examining cheapest_path->parent, though). However, correct selection of the Paths involved a significant amount of coupling between query_planner and grouping_planner, a problem which has gotten worse over time. It seems best to give up on this API choice and instead return the topmost RelOptInfo explicitly. Then grouping_planner can pull out the Paths it wants from the rel's path list. In this way we can remove all knowledge of grouping behaviors from query_planner. The only real benefit of the old way is that in the case of an empty FROM clause, we never made any RelOptInfos at all, just a Path. Now we have to gin up a dummy RelOptInfo to represent the empty FROM clause. That's not a very big deal though. While at it, simplify query_planner's API a bit more by having the caller set up root->tuple_fraction and root->limit_tuples, rather than passing those values as separate parameters. Since query_planner no longer does anything with either value, requiring it to fill the PlannerInfo fields seemed pretty arbitrary. This patch just rearranges code; it doesn't (intentionally) change any behaviors. Followup patches will do more interesting things.
2013-08-05 21:00:57 +02:00
* Get the best presorted path, that being the one that's cheapest for
* fetching just one row. If there's no such path, fail.
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
*/
Simplify query_planner's API by having it return the top-level RelOptInfo. Formerly, query_planner returned one or possibly two Paths for the topmost join relation, so that grouping_planner didn't see the join RelOptInfo (at least not directly; it didn't have any hesitation about examining cheapest_path->parent, though). However, correct selection of the Paths involved a significant amount of coupling between query_planner and grouping_planner, a problem which has gotten worse over time. It seems best to give up on this API choice and instead return the topmost RelOptInfo explicitly. Then grouping_planner can pull out the Paths it wants from the rel's path list. In this way we can remove all knowledge of grouping behaviors from query_planner. The only real benefit of the old way is that in the case of an empty FROM clause, we never made any RelOptInfos at all, just a Path. Now we have to gin up a dummy RelOptInfo to represent the empty FROM clause. That's not a very big deal though. While at it, simplify query_planner's API a bit more by having the caller set up root->tuple_fraction and root->limit_tuples, rather than passing those values as separate parameters. Since query_planner no longer does anything with either value, requiring it to fill the PlannerInfo fields seemed pretty arbitrary. This patch just rearranges code; it doesn't (intentionally) change any behaviors. Followup patches will do more interesting things.
2013-08-05 21:00:57 +02:00
if (final_rel->rows > 1.0)
path_fraction = 1.0 / final_rel->rows;
else
path_fraction = 1.0;
sorted_path =
get_cheapest_fractional_path_for_pathkeys(final_rel->pathlist,
subroot->query_pathkeys,
NULL,
path_fraction);
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
if (!sorted_path)
Simplify query_planner's API by having it return the top-level RelOptInfo. Formerly, query_planner returned one or possibly two Paths for the topmost join relation, so that grouping_planner didn't see the join RelOptInfo (at least not directly; it didn't have any hesitation about examining cheapest_path->parent, though). However, correct selection of the Paths involved a significant amount of coupling between query_planner and grouping_planner, a problem which has gotten worse over time. It seems best to give up on this API choice and instead return the topmost RelOptInfo explicitly. Then grouping_planner can pull out the Paths it wants from the rel's path list. In this way we can remove all knowledge of grouping behaviors from query_planner. The only real benefit of the old way is that in the case of an empty FROM clause, we never made any RelOptInfos at all, just a Path. Now we have to gin up a dummy RelOptInfo to represent the empty FROM clause. That's not a very big deal though. While at it, simplify query_planner's API a bit more by having the caller set up root->tuple_fraction and root->limit_tuples, rather than passing those values as separate parameters. Since query_planner no longer does anything with either value, requiring it to fill the PlannerInfo fields seemed pretty arbitrary. This patch just rearranges code; it doesn't (intentionally) change any behaviors. Followup patches will do more interesting things.
2013-08-05 21:00:57 +02:00
return false;
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
/*
* The path might not return exactly what we want, so fix that. (We
* assume that this won't change any conclusions about which was the
* cheapest path.)
*/
sorted_path = apply_projection_to_path(subroot, final_rel, sorted_path,
Refactor planning of projection steps that don't need a Result plan node. The original upper-planner-pathification design (commit 3fc6e2d7f5b652b4) assumed that we could always determine during Path formation whether or not we would need a Result plan node to perform projection of a targetlist. That turns out not to work very well, though, because createplan.c still has some responsibilities for choosing the specific target list associated with sorting/grouping nodes (in particular it might choose to add resjunk columns for sorting). We might not ever refactor that --- doing so would push more work into Path formation, which isn't attractive --- and we certainly won't do so for 9.6. So, while create_projection_path and apply_projection_to_path can tell for sure what will happen if the subpath is projection-capable, they can't tell for sure when it isn't. This is at least a latent bug in apply_projection_to_path, which might think it can apply a target to a non-projecting node when the node will end up computing something different. Also, I'd tied the creation of a ProjectionPath node to whether or not a Result is needed, but it turns out that we sometimes need a ProjectionPath node anyway to avoid modifying a possibly-shared subpath node. Callers had to use create_projection_path for such cases, and we added code to them that knew about the potential omission of a Result node and attempted to adjust the cost estimates for that. That was uncertainly correct and definitely ugly/unmaintainable. To fix, have create_projection_path explicitly check whether a Result is needed and adjust its cost estimate accordingly, though it creates a ProjectionPath in either case. apply_projection_to_path is now mostly just an optimized version that can avoid creating an extra Path node when the input is known to not be shared with any other live path. (There is one case that create_projection_path doesn't handle, which is pushing parallel-safe expressions below a Gather node. We could make it do that by duplicating the GatherPath, but there seems no need as yet.) create_projection_plan still has to recheck the tlist-match condition, which means that if the matching situation does get changed by createplan.c then we'll have made a slightly incorrect cost estimate. But there seems no help for that in the near term, and I doubt it occurs often enough, let alone would change planning decisions often enough, to be worth stressing about. I added a "dummypp" field to ProjectionPath to track whether create_projection_path thinks a Result is needed. This is not really necessary as-committed because create_projection_plan doesn't look at the flag; but it seems like a good idea to remember what we thought when forming the cost estimate, if only for debugging purposes. In passing, get rid of the target_parallel parameter added to apply_projection_to_path by commit 54f5c5150. I don't think that's a good idea because it involves callers in what should be an internal decision, and opens us up to missing optimization opportunities if callers think they don't need to provide a valid flag, as most don't. For the moment, this just costs us an extra has_parallel_hazard call when planning a Gather. If that starts to look expensive, I think a better solution would be to teach PathTarget to carry/cache knowledge of parallel-safety of its contents.
2016-06-22 00:38:20 +02:00
create_pathtarget(subroot, tlist));
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
/*
* Determine cost to get just the first row of the presorted path.
*
* Note: cost calculation here should match
* compare_fractional_path_costs().
*/
path_cost = sorted_path->startup_cost +
path_fraction * (sorted_path->total_cost - sorted_path->startup_cost);
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
/* Save state for further processing */
mminfo->subroot = subroot;
mminfo->path = sorted_path;
mminfo->pathcost = path_cost;
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
Reimplement planner's handling of MIN/MAX aggregate optimization (again). Instead of playing cute games with pathkeys, just build a direct representation of the intended sub-select, and feed it through query_planner to get a Path for the index access. This is a bit slower than 9.1's previous method, since we'll duplicate most of the overhead of query_planner; but since the whole optimization only applies to rather simple single-table queries, that probably won't be much of a problem in practice. The advantage is that we get to do the right thing when there's a partial index that needs the implicit IS NOT NULL clause to be usable. Also, although this makes planagg.c be a bit more closely tied to the ordering of operations in grouping_planner, we can get rid of some coupling to lower-level parts of the planner. Per complaint from Marti Raudsepp.
2011-03-22 05:34:31 +01:00
return true;
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
}
Postpone creation of pathkeys lists to fix bug #8049. This patch gets rid of the concept of, and infrastructure for, non-canonical PathKeys; we now only ever create canonical pathkey lists. The need for non-canonical pathkeys came from the desire to have grouping_planner initialize query_pathkeys and related pathkey lists before calling query_planner. However, since query_planner didn't actually *do* anything with those lists before they'd been made canonical, we can get rid of the whole mess by just not creating the lists at all until the point where we formerly canonicalized them. There are several ways in which we could implement that without making query_planner itself deal with grouping/sorting features (which are supposed to be the province of grouping_planner). I chose to add a callback function to query_planner's API; other alternatives would have required adding more fields to PlannerInfo, which while not bad in itself would create an ABI break for planner-related plugins in the 9.2 release series. This still breaks ABI for anything that calls query_planner directly, but it seems somewhat unlikely that there are any such plugins. I had originally conceived of this change as merely a step on the way to fixing bug #8049 from Teun Hoogendoorn; but it turns out that this fixes that bug all by itself, as per the added regression test. The reason is that now get_eclass_for_sort_expr is adding the ORDER BY expression at the end of EquivalenceClass creation not the start, and so anything that is in a multi-member EquivalenceClass has already been created with correct em_nullable_relids. I am suspicious that there are related scenarios in which we still need to teach get_eclass_for_sort_expr to compute correct nullable_relids, but am not eager to risk destabilizing either 9.2 or 9.3 to fix bugs that are only hypothetical. So for the moment, do this and stop here. Back-patch to 9.2 but not to earlier branches, since they don't exhibit this bug for lack of join-clause-movement logic that depends on em_nullable_relids being correct. (We might have to revisit that choice if any related bugs turn up.) In 9.2, don't change the signature of make_pathkeys_for_sortclauses nor remove canonicalize_pathkeys, so as not to risk more plugin breakage than we have to.
2013-04-29 20:49:01 +02:00
/*
Make the upper part of the planner work by generating and comparing Paths. I've been saying we needed to do this for more than five years, and here it finally is. This patch removes the ever-growing tangle of spaghetti logic that grouping_planner() used to use to try to identify the best plan for post-scan/join query steps. Now, there is (nearly) independent consideration of each execution step, and entirely separate construction of Paths to represent each of the possible ways to do that step. We choose the best Path or set of Paths using the same add_path() logic that's been used inside query_planner() for years. In addition, this patch removes the old restriction that subquery_planner() could return only a single Plan. It now returns a RelOptInfo containing a set of Paths, just as query_planner() does, and the parent query level can use each of those Paths as the basis of a SubqueryScanPath at its level. This allows finding some optimizations that we missed before, wherein a subquery was capable of returning presorted data and thereby avoiding a sort in the parent level, making the overall cost cheaper even though delivering sorted output was not the cheapest plan for the subquery in isolation. (A couple of regression test outputs change in consequence of that. However, there is very little change in visible planner behavior overall, because the point of this patch is not to get immediate planning benefits but to create the infrastructure for future improvements.) There is a great deal left to do here. This patch unblocks a lot of planner work that was basically impractical in the old code structure, such as allowing FDWs to implement remote aggregation, or rewriting plan_set_operations() to allow consideration of multiple implementation orders for set operations. (The latter will likely require a full rewrite of plan_set_operations(); what I've done here is only to fix it to return Paths not Plans.) I have also left unfinished some localized refactoring in createplan.c and planner.c, because it was not necessary to get this patch to a working state. Thanks to Robert Haas, David Rowley, and Amit Kapila for review.
2016-03-07 21:58:22 +01:00
* Compute query_pathkeys and other pathkeys during query_planner()
Postpone creation of pathkeys lists to fix bug #8049. This patch gets rid of the concept of, and infrastructure for, non-canonical PathKeys; we now only ever create canonical pathkey lists. The need for non-canonical pathkeys came from the desire to have grouping_planner initialize query_pathkeys and related pathkey lists before calling query_planner. However, since query_planner didn't actually *do* anything with those lists before they'd been made canonical, we can get rid of the whole mess by just not creating the lists at all until the point where we formerly canonicalized them. There are several ways in which we could implement that without making query_planner itself deal with grouping/sorting features (which are supposed to be the province of grouping_planner). I chose to add a callback function to query_planner's API; other alternatives would have required adding more fields to PlannerInfo, which while not bad in itself would create an ABI break for planner-related plugins in the 9.2 release series. This still breaks ABI for anything that calls query_planner directly, but it seems somewhat unlikely that there are any such plugins. I had originally conceived of this change as merely a step on the way to fixing bug #8049 from Teun Hoogendoorn; but it turns out that this fixes that bug all by itself, as per the added regression test. The reason is that now get_eclass_for_sort_expr is adding the ORDER BY expression at the end of EquivalenceClass creation not the start, and so anything that is in a multi-member EquivalenceClass has already been created with correct em_nullable_relids. I am suspicious that there are related scenarios in which we still need to teach get_eclass_for_sort_expr to compute correct nullable_relids, but am not eager to risk destabilizing either 9.2 or 9.3 to fix bugs that are only hypothetical. So for the moment, do this and stop here. Back-patch to 9.2 but not to earlier branches, since they don't exhibit this bug for lack of join-clause-movement logic that depends on em_nullable_relids being correct. (We might have to revisit that choice if any related bugs turn up.) In 9.2, don't change the signature of make_pathkeys_for_sortclauses nor remove canonicalize_pathkeys, so as not to risk more plugin breakage than we have to.
2013-04-29 20:49:01 +02:00
*/
static void
minmax_qp_callback(PlannerInfo *root, void *extra)
{
root->group_pathkeys = NIL;
root->window_pathkeys = NIL;
root->distinct_pathkeys = NIL;
root->sort_pathkeys =
make_pathkeys_for_sortclauses(root,
root->parse->sortClause,
root->parse->targetList);
root->query_pathkeys = root->sort_pathkeys;
}
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
/*
* Get the OID of the sort operator, if any, associated with an aggregate.
* Returns InvalidOid if there is no such operator.
*/
static Oid
fetch_agg_sort_op(Oid aggfnoid)
{
HeapTuple aggTuple;
Form_pg_aggregate aggform;
Oid aggsortop;
/* fetch aggregate entry from pg_aggregate */
Wrap calls to SearchSysCache and related functions using macros. The purpose of this change is to eliminate the need for every caller of SearchSysCache, SearchSysCacheCopy, SearchSysCacheExists, GetSysCacheOid, and SearchSysCacheList to know the maximum number of allowable keys for a syscache entry (currently 4). This will make it far easier to increase the maximum number of keys in a future release should we choose to do so, and it makes the code shorter, too. Design and review by Tom Lane.
2010-02-14 19:42:19 +01:00
aggTuple = SearchSysCache1(AGGFNOID, ObjectIdGetDatum(aggfnoid));
Create the planner mechanism for optimizing simple MIN and MAX queries into indexscans on matching indexes. For the moment, it only handles int4 and text datatypes; next step is to add a column to pg_aggregate so that all MIN/MAX aggregates can be handled. Per my recent proposal.
2005-04-12 01:06:57 +02:00
if (!HeapTupleIsValid(aggTuple))
return InvalidOid;
aggform = (Form_pg_aggregate) GETSTRUCT(aggTuple);
aggsortop = aggform->aggsortop;
ReleaseSysCache(aggTuple);
return aggsortop;
}