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postgresql/src/backend/optimizer/path/indxpath.c

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/*-------------------------------------------------------------------------
*
* indxpath.c
* Routines to determine which indexes are usable for scanning a
* given relation, and create Paths accordingly.
*
* Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/optimizer/path/indxpath.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <math.h>
#include "access/skey.h"
#include "access/sysattr.h"
#include "catalog/pg_am.h"
#include "catalog/pg_collation.h"
#include "catalog/pg_operator.h"
#include "catalog/pg_opfamily.h"
#include "catalog/pg_type.h"
#include "nodes/makefuncs.h"
#include "optimizer/clauses.h"
#include "optimizer/cost.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/predtest.h"
#include "optimizer/restrictinfo.h"
#include "optimizer/var.h"
#include "utils/builtins.h"
#include "utils/bytea.h"
#include "utils/lsyscache.h"
#include "utils/pg_locale.h"
#include "utils/selfuncs.h"
#define IsBooleanOpfamily(opfamily) \
((opfamily) == BOOL_BTREE_FAM_OID || (opfamily) == BOOL_HASH_FAM_OID)
#define IndexCollMatchesExprColl(idxcollation, exprcollation) \
((idxcollation) == InvalidOid || (idxcollation) == (exprcollation))
/* Whether to use ScalarArrayOpExpr to build index qualifications */
typedef enum
{
SAOP_PER_AM, /* Use ScalarArrayOpExpr if amsearcharray */
SAOP_ALLOW, /* Use ScalarArrayOpExpr for all indexes */
SAOP_REQUIRE /* Require ScalarArrayOpExpr to be used */
} SaOpControl;
/* Whether we are looking for plain indexscan, bitmap scan, or either */
typedef enum
{
ST_INDEXSCAN, /* must support amgettuple */
ST_BITMAPSCAN, /* must support amgetbitmap */
ST_ANYSCAN /* either is okay */
} ScanTypeControl;
/* Data structure for collecting qual clauses that match an index */
typedef struct
{
bool nonempty; /* True if lists are not all empty */
/* Lists of RestrictInfos, one per index column */
List *indexclauses[INDEX_MAX_KEYS];
} IndexClauseSet;
/* Per-path data used within choose_bitmap_and() */
typedef struct
{
Path *path; /* IndexPath, BitmapAndPath, or BitmapOrPath */
List *quals; /* the WHERE clauses it uses */
List *preds; /* predicates of its partial index(es) */
Bitmapset *clauseids; /* quals+preds represented as a bitmapset */
} PathClauseUsage;
static void consider_index_join_clauses(PlannerInfo *root, RelOptInfo *rel,
IndexOptInfo *index,
IndexClauseSet *rclauseset,
IndexClauseSet *jclauseset,
IndexClauseSet *eclauseset,
List **bitindexpaths);
static void expand_eclass_clause_combinations(PlannerInfo *root,
RelOptInfo *rel,
IndexOptInfo *index,
int thiscol, int lastcol,
IndexClauseSet *clauseset,
IndexClauseSet *eclauseset,
List **bitindexpaths);
static void get_index_paths(PlannerInfo *root, RelOptInfo *rel,
IndexOptInfo *index, IndexClauseSet *clauses,
List **bitindexpaths);
static List *build_index_paths(PlannerInfo *root, RelOptInfo *rel,
IndexOptInfo *index, IndexClauseSet *clauses,
bool useful_predicate,
SaOpControl saop_control, ScanTypeControl scantype);
static List *build_paths_for_OR(PlannerInfo *root, RelOptInfo *rel,
List *clauses, List *other_clauses);
static List *drop_indexable_join_clauses(RelOptInfo *rel, List *clauses);
static Path *choose_bitmap_and(PlannerInfo *root, RelOptInfo *rel,
List *paths);
static int path_usage_comparator(const void *a, const void *b);
static Cost bitmap_scan_cost_est(PlannerInfo *root, RelOptInfo *rel,
Path *ipath);
static Cost bitmap_and_cost_est(PlannerInfo *root, RelOptInfo *rel,
List *paths);
static PathClauseUsage *classify_index_clause_usage(Path *path,
List **clauselist);
static void find_indexpath_quals(Path *bitmapqual, List **quals, List **preds);
static int find_list_position(Node *node, List **nodelist);
static bool check_index_only(RelOptInfo *rel, IndexOptInfo *index);
static double get_loop_count(PlannerInfo *root, Relids outer_relids);
static void match_restriction_clauses_to_index(RelOptInfo *rel,
IndexOptInfo *index,
IndexClauseSet *clauseset);
static void match_join_clauses_to_index(PlannerInfo *root,
RelOptInfo *rel, IndexOptInfo *index,
IndexClauseSet *clauseset,
List **joinorclauses);
static void match_eclass_clauses_to_index(PlannerInfo *root,
IndexOptInfo *index,
IndexClauseSet *clauseset);
static void match_clauses_to_index(IndexOptInfo *index,
List *clauses,
IndexClauseSet *clauseset);
static void match_clause_to_index(IndexOptInfo *index,
RestrictInfo *rinfo,
IndexClauseSet *clauseset);
static bool match_clause_to_indexcol(IndexOptInfo *index,
int indexcol,
RestrictInfo *rinfo);
static bool is_indexable_operator(Oid expr_op, Oid opfamily,
bool indexkey_on_left);
static bool match_rowcompare_to_indexcol(IndexOptInfo *index,
int indexcol,
Oid opfamily,
Oid idxcollation,
RowCompareExpr *clause);
static void match_pathkeys_to_index(IndexOptInfo *index, List *pathkeys,
List **orderby_clauses_p,
List **clause_columns_p);
static Expr *match_clause_to_ordering_op(IndexOptInfo *index,
int indexcol, Expr *clause, Oid pk_opfamily);
static bool match_boolean_index_clause(Node *clause, int indexcol,
IndexOptInfo *index);
static bool match_special_index_operator(Expr *clause,
Oid opfamily, Oid idxcollation,
bool indexkey_on_left);
static Expr *expand_boolean_index_clause(Node *clause, int indexcol,
IndexOptInfo *index);
static List *expand_indexqual_opclause(RestrictInfo *rinfo,
Oid opfamily, Oid idxcollation);
static RestrictInfo *expand_indexqual_rowcompare(RestrictInfo *rinfo,
IndexOptInfo *index,
int indexcol);
static List *prefix_quals(Node *leftop, Oid opfamily, Oid collation,
Const *prefix, Pattern_Prefix_Status pstatus);
static List *network_prefix_quals(Node *leftop, Oid expr_op, Oid opfamily,
Datum rightop);
static Datum string_to_datum(const char *str, Oid datatype);
static Const *string_to_const(const char *str, Oid datatype);
/*
* create_index_paths()
* Generate all interesting index paths for the given relation.
* Candidate paths are added to the rel's pathlist (using add_path).
*
* To be considered for an index scan, an index must match one or more
* restriction clauses or join clauses from the query's qual condition,
* or match the query's ORDER BY condition, or have a predicate that
* matches the query's qual condition.
*
* There are two basic kinds of index scans. A "plain" index scan uses
* only restriction clauses (possibly none at all) in its indexqual,
* so it can be applied in any context. A "parameterized" index scan uses
* join clauses (plus restriction clauses, if available) in its indexqual.
* When joining such a scan to one of the relations supplying the other
* variables used in its indexqual, the parameterized scan must appear as
* the inner relation of a nestloop join; it can't be used on the outer side,
* nor in a merge or hash join. In that context, values for the other rels'
* attributes are available and fixed during any one scan of the indexpath.
*
* An IndexPath is generated and submitted to add_path() for each plain or
* parameterized index scan this routine deems potentially interesting for
* the current query.
*
* 'rel' is the relation for which we want to generate index paths
*
* Note: check_partial_indexes() must have been run previously for this rel.
*/
void
create_index_paths(PlannerInfo *root, RelOptInfo *rel)
{
List *indexpaths;
List *bitindexpaths;
List *bitjoinpaths;
List *joinorclauses;
IndexClauseSet rclauseset;
IndexClauseSet jclauseset;
IndexClauseSet eclauseset;
ListCell *ilist;
/* Skip the whole mess if no indexes */
if (rel->indexlist == NIL)
return;
/* Bitmap paths are collected and then dealt with at the end */
bitindexpaths = bitjoinpaths = joinorclauses = NIL;
/* Examine each index in turn */
foreach(ilist, rel->indexlist)
{
IndexOptInfo *index = (IndexOptInfo *) lfirst(ilist);
/* Protect limited-size array in IndexClauseSets */
Assert(index->ncolumns <= INDEX_MAX_KEYS);
/*
* Ignore partial indexes that do not match the query.
* (generate_bitmap_or_paths() might be able to do something with
* them, but that's of no concern here.)
*/
if (index->indpred != NIL && !index->predOK)
continue;
/*
* Identify the restriction clauses that can match the index.
*/
MemSet(&rclauseset, 0, sizeof(rclauseset));
match_restriction_clauses_to_index(rel, index, &rclauseset);
/*
* Build index paths from the restriction clauses. These will be
* non-parameterized paths. Plain paths go directly to add_path(),
* bitmap paths are added to bitindexpaths to be handled below.
*/
get_index_paths(root, rel, index, &rclauseset,
&bitindexpaths);
/*
* Identify the join clauses that can match the index. For the moment
* we keep them separate from the restriction clauses. Note that
* this finds only "loose" join clauses that have not been merged
* into EquivalenceClasses. Also, collect join OR clauses for later.
*/
MemSet(&jclauseset, 0, sizeof(jclauseset));
match_join_clauses_to_index(root, rel, index,
&jclauseset, &joinorclauses);
/*
* Look for EquivalenceClasses that can generate joinclauses
* matching the index.
*/
MemSet(&eclauseset, 0, sizeof(eclauseset));
match_eclass_clauses_to_index(root, index, &eclauseset);
/*
* If we found any plain or eclass join clauses, decide what to
* do with 'em.
*/
if (jclauseset.nonempty || eclauseset.nonempty)
consider_index_join_clauses(root, rel, index,
&rclauseset,
&jclauseset,
&eclauseset,
&bitjoinpaths);
}
/*
* Generate BitmapOrPaths for any suitable OR-clauses present in the
* restriction list. Add these to bitindexpaths.
*/
indexpaths = generate_bitmap_or_paths(root, rel,
rel->baserestrictinfo, NIL,
false);
bitindexpaths = list_concat(bitindexpaths, indexpaths);
/*
* Likewise, generate BitmapOrPaths for any suitable OR-clauses present in
* the joinclause list. Add these to bitjoinpaths.
*/
indexpaths = generate_bitmap_or_paths(root, rel,
joinorclauses, rel->baserestrictinfo,
false);
bitjoinpaths = list_concat(bitjoinpaths, indexpaths);
/*
* If we found anything usable, generate a BitmapHeapPath for the most
* promising combination of restriction bitmap index paths. Note there
* will be only one such path no matter how many indexes exist. This
* should be sufficient since there's basically only one figure of merit
* (total cost) for such a path.
*/
if (bitindexpaths != NIL)
{
Path *bitmapqual;
BitmapHeapPath *bpath;
bitmapqual = choose_bitmap_and(root, rel, bitindexpaths);
bpath = create_bitmap_heap_path(root, rel, bitmapqual, 1.0);
add_path(rel, (Path *) bpath);
}
/*
* Likewise, if we found anything usable, generate a BitmapHeapPath for
* the most promising combination of join bitmap index paths. Note there
* will be only one such path no matter how many join clauses are
* available. (XXX is that good enough, or do we need to consider even
* more paths for different subsets of possible join partners? Also,
* should we add in restriction bitmap paths as well?)
*/
if (bitjoinpaths != NIL)
{
Path *bitmapqual;
double loop_count;
BitmapHeapPath *bpath;
bitmapqual = choose_bitmap_and(root, rel, bitjoinpaths);
loop_count = get_loop_count(root, bitmapqual->required_outer);
bpath = create_bitmap_heap_path(root, rel, bitmapqual, loop_count);
add_path(rel, (Path *) bpath);
}
}
/*
* consider_index_join_clauses
* Given sets of join clauses for an index, decide which parameterized
* index paths to build.
*
* Plain indexpaths are sent directly to add_path, while potential
* bitmap indexpaths are added to *bitindexpaths for later processing.
*
* 'rel' is the index's heap relation
* 'index' is the index for which we want to generate paths
* 'rclauseset' is the collection of indexable restriction clauses
* 'jclauseset' is the collection of indexable simple join clauses
* 'eclauseset' is the collection of indexable clauses from EquivalenceClasses
* '*bitindexpaths' is the list to add bitmap paths to
*
* Note: this changes the clause lists contained in the passed clausesets,
* but we don't care since the caller is done with them.
*/
static void
consider_index_join_clauses(PlannerInfo *root, RelOptInfo *rel,
IndexOptInfo *index,
IndexClauseSet *rclauseset,
IndexClauseSet *jclauseset,
IndexClauseSet *eclauseset,
List **bitindexpaths)
{
IndexClauseSet clauseset;
int last_eclass_col;
int indexcol;
/*
* We can always include any restriction clauses in the index clauses.
* However, it's not obvious which subsets of the join clauses are worth
* generating paths from, and it's unlikely that considering every
* possible subset is worth the cycles. Our current heuristic is based
* on the index columns, with the idea that later index columns are less
* useful than earlier ones; therefore it's unlikely to be worth trying
* combinations that would remove a clause from an earlier index column
* while adding one to a later column. Also, we know that all the
* eclass clauses for a particular column are redundant, so we should
* use only one of them. However, eclass clauses will always represent
* equality which is the strongest type of index constraint, so those
* are high-value and we should try every available combination when we
* have eclass clauses for more than one column. Furthermore, it's
* unlikely to be useful to combine an eclass clause with non-eclass
* clauses for the same index column. These considerations lead to the
* following heuristics:
*
* First, start with the restriction clauses, and add on all simple join
* clauses for column 1. If there are any such join clauses, generate
* paths with this collection of clauses. Then, if there are eclass
* clauses for column 1, generate paths with each one of them replacing
* any other clauses we have for column 1.
*
* Next, add on all simple join clauses for column 2. If there are any
* such join clauses, generate paths with this collection. If there are
* eclass clauses for columns 1 or 2, generate paths with each such clause
* replacing other clauses for its index column, including cases where we
* use restriction or simple join clauses for one column and an eclass
* clause for the other.
*
* Repeat for each additional index column.
*/
/* Set up working set with just the restriction clauses */
memcpy(&clauseset, rclauseset, sizeof(clauseset));
/* Even if it's empty right now, it won't be by the time we use it */
clauseset.nonempty = true;
last_eclass_col = -1;
for (indexcol = 0; indexcol < index->ncolumns; indexcol++)
{
/*
* If we don't have either simple join clauses or eclass clauses for
* this column, no new paths can be created in this iteration.
*/
if (jclauseset->indexclauses[indexcol] == NIL &&
eclauseset->indexclauses[indexcol] == NIL)
continue;
/* Add any simple join clauses to the working set */
clauseset.indexclauses[indexcol] =
list_concat(clauseset.indexclauses[indexcol],
jclauseset->indexclauses[indexcol]);
/* Set recursion depth to reach last col with eclass clauses */
if (eclauseset->indexclauses[indexcol] != NIL)
last_eclass_col = indexcol;
/* Do we have eclass clauses for any column now under consideration? */
if (last_eclass_col >= 0)
{
/* Yes, so recursively generate all eclass clause combinations */
expand_eclass_clause_combinations(root, rel, index,
0, last_eclass_col,
&clauseset, eclauseset,
bitindexpaths);
}
else
{
/* No, consider the newly-enlarged set of simple join clauses */
get_index_paths(root, rel, index, &clauseset, bitindexpaths);
}
}
}
/*
* expand_eclass_clause_combinations
* Generate all combinations of eclass join clauses for first N columns,
* and construct parameterized index paths for each combination.
*
* Workhorse for consider_index_join_clauses; see notes therein for rationale.
* It's convenient to use recursion to implement the enumeration, since we
* can have at most INDEX_MAX_KEYS recursion levels.
*
* 'rel', 'index', 'eclauseset', 'bitindexpaths' as above
* 'thiscol' is the current index column number/recursion level
* 'lastcol' is the last index column we should consider eclass clauses for
* 'clauseset' is the current collection of indexable clauses
*/
static void
expand_eclass_clause_combinations(PlannerInfo *root, RelOptInfo *rel,
IndexOptInfo *index,
int thiscol, int lastcol,
IndexClauseSet *clauseset,
IndexClauseSet *eclauseset,
List **bitindexpaths)
{
List *save_clauses;
ListCell *lc;
/* If past last eclass column, end the recursion and generate paths */
if (thiscol > lastcol)
{
get_index_paths(root, rel, index, clauseset, bitindexpaths);
return;
}
/* If no eclass clauses to consider for this column, just recurse */
if (eclauseset->indexclauses[thiscol] == NIL)
{
Assert(thiscol < lastcol);
expand_eclass_clause_combinations(root, rel, index,
thiscol + 1, lastcol,
clauseset, eclauseset,
bitindexpaths);
return;
}
/* We'll momentarily save and restore the list of non-eclass clauses */
save_clauses = clauseset->indexclauses[thiscol];
/* If we have non-eclass clauses for this column, first try with those */
if (save_clauses)
expand_eclass_clause_combinations(root, rel, index,
thiscol + 1, lastcol,
clauseset, eclauseset,
bitindexpaths);
/* For each eclass clause alternative ... */
foreach(lc, eclauseset->indexclauses[thiscol])
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
/* Replace any existing clauses with the eclass clause */
clauseset->indexclauses[thiscol] = list_make1(rinfo);
/* Recurse to advance to next column */
expand_eclass_clause_combinations(root, rel, index,
thiscol + 1, lastcol,
clauseset, eclauseset,
bitindexpaths);
}
/* Restore previous list contents */
clauseset->indexclauses[thiscol] = save_clauses;
}
/*
* get_index_paths
* Given an index and a set of index clauses for it, construct IndexPaths.
*
* Plain indexpaths are sent directly to add_path, while potential
* bitmap indexpaths are added to *bitindexpaths for later processing.
*
* This is a fairly simple frontend to build_index_paths(). Its reason for
* existence is mainly to handle ScalarArrayOpExpr quals properly. If the
* index AM supports them natively, we should just include them in simple
* index paths. If not, we should exclude them while building simple index
* paths, and then make a separate attempt to include them in bitmap paths.
*/
static void
get_index_paths(PlannerInfo *root, RelOptInfo *rel,
IndexOptInfo *index, IndexClauseSet *clauses,
List **bitindexpaths)
{
List *indexpaths;
ListCell *lc;
/*
* Build simple index paths using the clauses. Allow ScalarArrayOpExpr
* clauses only if the index AM supports them natively.
*/
indexpaths = build_index_paths(root, rel,
index, clauses,
index->predOK,
SAOP_PER_AM, ST_ANYSCAN);
/*
* Submit all the ones that can form plain IndexScan plans to add_path.
* (A plain IndexPath can represent either a plain IndexScan or an
* IndexOnlyScan, but for our purposes here that distinction does not
* matter. However, some of the indexes might support only bitmap scans,
* and those we mustn't submit to add_path here.)
*
* Also, pick out the ones that are usable as bitmap scans. For that,
* we must discard indexes that don't support bitmap scans, and we
* also are only interested in paths that have some selectivity; we
* should discard anything that was generated solely for ordering
* purposes.
*/
foreach(lc, indexpaths)
{
IndexPath *ipath = (IndexPath *) lfirst(lc);
if (index->amhasgettuple)
add_path(rel, (Path *) ipath);
if (index->amhasgetbitmap &&
(ipath->path.pathkeys == NIL ||
ipath->indexselectivity < 1.0))
*bitindexpaths = lappend(*bitindexpaths, ipath);
}
/*
* If the index doesn't handle ScalarArrayOpExpr clauses natively,
* check to see if there are any such clauses, and if so generate
* bitmap scan paths relying on executor-managed ScalarArrayOpExpr.
*/
if (!index->amsearcharray)
{
indexpaths = build_index_paths(root, rel,
index, clauses,
false,
SAOP_REQUIRE, ST_BITMAPSCAN);
*bitindexpaths = list_concat(*bitindexpaths, indexpaths);
}
}
/*
* build_index_paths
* Given an index and a set of index clauses for it, construct zero
* or more IndexPaths.
*
* We return a list of paths because (1) this routine checks some cases
* that should cause us to not generate any IndexPath, and (2) in some
* cases we want to consider both a forward and a backward scan, so as
* to obtain both sort orders. Note that the paths are just returned
* to the caller and not immediately fed to add_path().
*
* At top level, useful_predicate should be exactly the index's predOK flag
* (ie, true if it has a predicate that was proven from the restriction
* clauses). When working on an arm of an OR clause, useful_predicate
* should be true if the predicate required the current OR list to be proven.
* Note that this routine should never be called at all if the index has an
* unprovable predicate.
*
* saop_control indicates whether ScalarArrayOpExpr clauses can be used.
* When it's SAOP_REQUIRE, index paths are created only if we found at least
* one ScalarArrayOpExpr clause.
*
* scantype indicates whether we want to create plain indexscans, bitmap
* indexscans, or both. When it's ST_BITMAPSCAN, we will not consider
* index ordering while deciding if a Path is worth generating.
*
* 'rel' is the index's heap relation
* 'index' is the index for which we want to generate paths
* 'clauses' is the collection of indexable clauses (RestrictInfo nodes)
* 'useful_predicate' indicates whether the index has a useful predicate
* 'saop_control' indicates whether ScalarArrayOpExpr clauses can be used
* 'scantype' indicates whether we need plain or bitmap scan support
*/
static List *
build_index_paths(PlannerInfo *root, RelOptInfo *rel,
IndexOptInfo *index, IndexClauseSet *clauses,
bool useful_predicate,
SaOpControl saop_control, ScanTypeControl scantype)
{
List *result = NIL;
IndexPath *ipath;
List *index_clauses;
List *clause_columns;
Relids outer_relids;
double loop_count;
List *orderbyclauses;
List *orderbyclausecols;
List *index_pathkeys;
List *useful_pathkeys;
bool found_clause;
bool pathkeys_possibly_useful;
bool index_is_ordered;
bool index_only_scan;
int indexcol;
/*
* Check that index supports the desired scan type(s)
*/
switch (scantype)
{
case ST_INDEXSCAN:
if (!index->amhasgettuple)
return NIL;
break;
case ST_BITMAPSCAN:
if (!index->amhasgetbitmap)
return NIL;
break;
case ST_ANYSCAN:
/* either or both are OK */
break;
}
/*
* 1. Collect the index clauses into a single list.
*
* We build a list of RestrictInfo nodes for clauses to be used with
* this index, along with an integer list of the index column numbers
* (zero based) that each clause should be used with. The clauses are
* ordered by index key, so that the column numbers form a nondecreasing
* sequence. (This order is depended on by btree and possibly other
* places.) The lists can be empty, if the index AM allows that.
*
* found_clause is set true only if there's at least one index clause;
* and if saop_control is SAOP_REQUIRE, it has to be a ScalarArrayOpExpr
* clause.
*
* We also build a Relids set showing which outer rels are required
* by the selected clauses.
*/
index_clauses = NIL;
clause_columns = NIL;
found_clause = false;
outer_relids = NULL;
for (indexcol = 0; indexcol < index->ncolumns; indexcol++)
{
ListCell *lc;
foreach(lc, clauses->indexclauses[indexcol])
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
if (IsA(rinfo->clause, ScalarArrayOpExpr))
{
/* Ignore if not supported by index */
if (saop_control == SAOP_PER_AM && !index->amsearcharray)
continue;
found_clause = true;
}
else
{
if (saop_control != SAOP_REQUIRE)
found_clause = true;
}
index_clauses = lappend(index_clauses, rinfo);
clause_columns = lappend_int(clause_columns, indexcol);
outer_relids = bms_add_members(outer_relids,
rinfo->clause_relids);
}
/*
* If no clauses match the first index column, check for amoptionalkey
* restriction. We can't generate a scan over an index with
* amoptionalkey = false unless there's at least one index clause.
* (When working on columns after the first, this test cannot fail.
* It is always okay for columns after the first to not have any
* clauses.)
*/
if (index_clauses == NIL && !index->amoptionalkey)
return NIL;
}
/* We do not want the index's rel itself listed in outer_relids */
outer_relids = bms_del_member(outer_relids, rel->relid);
/* Enforce convention that outer_relids is exactly NULL if empty */
if (bms_is_empty(outer_relids))
outer_relids = NULL;
/* Compute loop_count for cost estimation purposes */
loop_count = get_loop_count(root, outer_relids);
/*
* 2. Compute pathkeys describing index's ordering, if any, then see how
* many of them are actually useful for this query. This is not relevant
* if we are only trying to build bitmap indexscans.
*/
pathkeys_possibly_useful = (scantype != ST_BITMAPSCAN &&
has_useful_pathkeys(root, rel));
index_is_ordered = (index->sortopfamily != NULL);
if (index_is_ordered && pathkeys_possibly_useful)
{
index_pathkeys = build_index_pathkeys(root, index,
ForwardScanDirection);
useful_pathkeys = truncate_useless_pathkeys(root, rel,
index_pathkeys);
orderbyclauses = NIL;
orderbyclausecols = NIL;
}
else if (index->amcanorderbyop && pathkeys_possibly_useful)
{
/* see if we can generate ordering operators for query_pathkeys */
match_pathkeys_to_index(index, root->query_pathkeys,
&orderbyclauses,
&orderbyclausecols);
if (orderbyclauses)
useful_pathkeys = root->query_pathkeys;
else
useful_pathkeys = NIL;
}
else
{
useful_pathkeys = NIL;
orderbyclauses = NIL;
orderbyclausecols = NIL;
}
/*
* 3. Check if an index-only scan is possible. If we're not building
* plain indexscans, this isn't relevant since bitmap scans don't support
* index data retrieval anyway.
*/
index_only_scan = (scantype != ST_BITMAPSCAN &&
check_index_only(rel, index));
/*
* 4. Generate an indexscan path if there are relevant restriction clauses
* in the current clauses, OR the index ordering is potentially useful for
* later merging or final output ordering, OR the index has a useful
* predicate, OR an index-only scan is possible.
*/
if (found_clause || useful_pathkeys != NIL || useful_predicate ||
index_only_scan)
{
ipath = create_index_path(root, index,
index_clauses,
clause_columns,
orderbyclauses,
orderbyclausecols,
useful_pathkeys,
index_is_ordered ?
ForwardScanDirection :
NoMovementScanDirection,
index_only_scan,
outer_relids,
loop_count);
result = lappend(result, ipath);
}
/*
* 5. If the index is ordered, a backwards scan might be interesting.
*/
if (index_is_ordered && pathkeys_possibly_useful)
{
index_pathkeys = build_index_pathkeys(root, index,
BackwardScanDirection);
useful_pathkeys = truncate_useless_pathkeys(root, rel,
index_pathkeys);
if (useful_pathkeys != NIL)
{
ipath = create_index_path(root, index,
index_clauses,
clause_columns,
NIL,
NIL,
useful_pathkeys,
BackwardScanDirection,
index_only_scan,
outer_relids,
loop_count);
result = lappend(result, ipath);
}
}
return result;
}
/*
* build_paths_for_OR
* Given a list of restriction clauses from one arm of an OR clause,
* construct all matching IndexPaths for the relation.
*
* Here we must scan all indexes of the relation, since a bitmap OR tree
* can use multiple indexes.
*
* The caller actually supplies two lists of restriction clauses: some
* "current" ones and some "other" ones. Both lists can be used freely
* to match keys of the index, but an index must use at least one of the
* "current" clauses to be considered usable. The motivation for this is
* examples like
* WHERE (x = 42) AND (... OR (y = 52 AND z = 77) OR ....)
* While we are considering the y/z subclause of the OR, we can use "x = 42"
* as one of the available index conditions; but we shouldn't match the
* subclause to any index on x alone, because such a Path would already have
* been generated at the upper level. So we could use an index on x,y,z
* or an index on x,y for the OR subclause, but not an index on just x.
* When dealing with a partial index, a match of the index predicate to
* one of the "current" clauses also makes the index usable.
*
* 'rel' is the relation for which we want to generate index paths
* 'clauses' is the current list of clauses (RestrictInfo nodes)
* 'other_clauses' is the list of additional upper-level clauses
*/
static List *
build_paths_for_OR(PlannerInfo *root, RelOptInfo *rel,
List *clauses, List *other_clauses)
{
List *result = NIL;
List *all_clauses = NIL; /* not computed till needed */
ListCell *lc;
foreach(lc, rel->indexlist)
{
IndexOptInfo *index = (IndexOptInfo *) lfirst(lc);
IndexClauseSet clauseset;
List *indexpaths;
bool useful_predicate;
/* Ignore index if it doesn't support bitmap scans */
if (!index->amhasgetbitmap)
continue;
/*
* Ignore partial indexes that do not match the query. If a partial
* index is marked predOK then we know it's OK. Otherwise, we have
* to test whether the added clauses are sufficient to imply the
* predicate. If so, we can use the index in the current context.
*
* We set useful_predicate to true iff the predicate was proven using
* the current set of clauses. This is needed to prevent matching a
* predOK index to an arm of an OR, which would be a legal but
* pointlessly inefficient plan. (A better plan will be generated by
* just scanning the predOK index alone, no OR.)
*/
useful_predicate = false;
if (index->indpred != NIL)
{
if (index->predOK)
{
/* Usable, but don't set useful_predicate */
}
else
{
/* Form all_clauses if not done already */
if (all_clauses == NIL)
all_clauses = list_concat(list_copy(clauses),
other_clauses);
if (!predicate_implied_by(index->indpred, all_clauses))
continue; /* can't use it at all */
if (!predicate_implied_by(index->indpred, other_clauses))
useful_predicate = true;
}
}
/*
* Identify the restriction clauses that can match the index.
*/
MemSet(&clauseset, 0, sizeof(clauseset));
match_clauses_to_index(index, clauses, &clauseset);
/*
* If no matches so far, and the index predicate isn't useful,
* we don't want it.
*/
if (!clauseset.nonempty && !useful_predicate)
continue;
/*
* Add "other" restriction clauses to the clauseset.
*/
match_clauses_to_index(index, other_clauses, &clauseset);
/*
* Construct paths if possible.
*/
indexpaths = build_index_paths(root, rel,
index, &clauseset,
useful_predicate,
SAOP_ALLOW, ST_BITMAPSCAN);
result = list_concat(result, indexpaths);
}
return result;
}
/*
* generate_bitmap_or_paths
* Look through the list of clauses to find OR clauses, and generate
* a BitmapOrPath for each one we can handle that way. Return a list
* of the generated BitmapOrPaths.
*
* other_clauses is a list of additional clauses that can be assumed true
* for the purpose of generating indexquals, but are not to be searched for
* ORs. (See build_paths_for_OR() for motivation.)
*
* If restriction_only is true, ignore OR elements that are join clauses.
* When using this feature it is caller's responsibility that neither clauses
* nor other_clauses contain any join clauses that are not ORs, as we do not
* re-filter those lists.
*/
List *
generate_bitmap_or_paths(PlannerInfo *root, RelOptInfo *rel,
List *clauses, List *other_clauses,
bool restriction_only)
{
List *result = NIL;
List *all_clauses;
ListCell *lc;
/*
* We can use both the current and other clauses as context for
* build_paths_for_OR; no need to remove ORs from the lists.
*/
all_clauses = list_concat(list_copy(clauses), other_clauses);
foreach(lc, clauses)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
List *pathlist;
Path *bitmapqual;
ListCell *j;
Assert(IsA(rinfo, RestrictInfo));
/* Ignore RestrictInfos that aren't ORs */
if (!restriction_is_or_clause(rinfo))
continue;
/*
* We must be able to match at least one index to each of the arms of
* the OR, else we can't use it.
*/
pathlist = NIL;
foreach(j, ((BoolExpr *) rinfo->orclause)->args)
{
Node *orarg = (Node *) lfirst(j);
List *indlist;
/* OR arguments should be ANDs or sub-RestrictInfos */
if (and_clause(orarg))
{
List *andargs = ((BoolExpr *) orarg)->args;
if (restriction_only)
andargs = drop_indexable_join_clauses(rel, andargs);
indlist = build_paths_for_OR(root, rel,
andargs,
all_clauses);
/* Recurse in case there are sub-ORs */
indlist = list_concat(indlist,
generate_bitmap_or_paths(root, rel,
andargs,
all_clauses,
restriction_only));
}
else
{
List *orargs;
Assert(IsA(orarg, RestrictInfo));
Assert(!restriction_is_or_clause((RestrictInfo *) orarg));
orargs = list_make1(orarg);
if (restriction_only)
orargs = drop_indexable_join_clauses(rel, orargs);
indlist = build_paths_for_OR(root, rel,
orargs,
all_clauses);
}
/*
* If nothing matched this arm, we can't do anything with this OR
* clause.
*/
if (indlist == NIL)
{
pathlist = NIL;
break;
}
/*
* OK, pick the most promising AND combination, and add it to
* pathlist.
*/
bitmapqual = choose_bitmap_and(root, rel, indlist);
pathlist = lappend(pathlist, bitmapqual);
}
/*
* If we have a match for every arm, then turn them into a
* BitmapOrPath, and add to result list.
*/
if (pathlist != NIL)
{
bitmapqual = (Path *) create_bitmap_or_path(root, rel, pathlist);
result = lappend(result, bitmapqual);
}
}
return result;
}
/*
* drop_indexable_join_clauses
* Remove any indexable join clauses from the list.
*
* This is a helper for generate_bitmap_or_paths(). We leave OR clauses
* in the list whether they are joins or not, since we might be able to
* extract a restriction item from an OR list. It's safe to leave such
* clauses in the list because match_clauses_to_index() will ignore them,
* so there's no harm in passing such clauses to build_paths_for_OR().
*/
static List *
drop_indexable_join_clauses(RelOptInfo *rel, List *clauses)
{
List *result = NIL;
ListCell *lc;
foreach(lc, clauses)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
Assert(IsA(rinfo, RestrictInfo));
if (restriction_is_or_clause(rinfo) ||
bms_is_subset(rinfo->clause_relids, rel->relids))
result = lappend(result, rinfo);
}
return result;
}
/*
* choose_bitmap_and
* Given a nonempty list of bitmap paths, AND them into one path.
*
* This is a nontrivial decision since we can legally use any subset of the
* given path set. We want to choose a good tradeoff between selectivity
* and cost of computing the bitmap.
*
* The result is either a single one of the inputs, or a BitmapAndPath
* combining multiple inputs.
*/
static Path *
choose_bitmap_and(PlannerInfo *root, RelOptInfo *rel, List *paths)
{
int npaths = list_length(paths);
PathClauseUsage **pathinfoarray;
PathClauseUsage *pathinfo;
List *clauselist;
List *bestpaths = NIL;
Cost bestcost = 0;
int i,
j;
ListCell *l;
Assert(npaths > 0); /* else caller error */
if (npaths == 1)
return (Path *) linitial(paths); /* easy case */
/*
* In theory we should consider every nonempty subset of the given paths.
* In practice that seems like overkill, given the crude nature of the
* estimates, not to mention the possible effects of higher-level AND and
* OR clauses. Moreover, it's completely impractical if there are a large
* number of paths, since the work would grow as O(2^N).
*
* As a heuristic, we first check for paths using exactly the same sets of
* WHERE clauses + index predicate conditions, and reject all but the
* cheapest-to-scan in any such group. This primarily gets rid of indexes
* that include the interesting columns but also irrelevant columns. (In
* situations where the DBA has gone overboard on creating variant
* indexes, this can make for a very large reduction in the number of
* paths considered further.)
*
* We then sort the surviving paths with the cheapest-to-scan first, and
* for each path, consider using that path alone as the basis for a bitmap
* scan. Then we consider bitmap AND scans formed from that path plus
* each subsequent (higher-cost) path, adding on a subsequent path if it
* results in a reduction in the estimated total scan cost. This means we
* consider about O(N^2) rather than O(2^N) path combinations, which is
* quite tolerable, especially given than N is usually reasonably small
* because of the prefiltering step. The cheapest of these is returned.
*
* We will only consider AND combinations in which no two indexes use the
* same WHERE clause. This is a bit of a kluge: it's needed because
* costsize.c and clausesel.c aren't very smart about redundant clauses.
* They will usually double-count the redundant clauses, producing a
* too-small selectivity that makes a redundant AND step look like it
* reduces the total cost. Perhaps someday that code will be smarter and
* we can remove this limitation. (But note that this also defends
* against flat-out duplicate input paths, which can happen because
* match_join_clauses_to_index will find the same OR join clauses that
* create_or_index_quals has pulled OR restriction clauses out of.)
*
* For the same reason, we reject AND combinations in which an index
* predicate clause duplicates another clause. Here we find it necessary
* to be even stricter: we'll reject a partial index if any of its
* predicate clauses are implied by the set of WHERE clauses and predicate
* clauses used so far. This covers cases such as a condition "x = 42"
* used with a plain index, followed by a clauseless scan of a partial
* index "WHERE x >= 40 AND x < 50". The partial index has been accepted
* only because "x = 42" was present, and so allowing it would partially
* double-count selectivity. (We could use predicate_implied_by on
* regular qual clauses too, to have a more intelligent, but much more
* expensive, check for redundancy --- but in most cases simple equality
* seems to suffice.)
*/
/*
* Extract clause usage info and detect any paths that use exactly the
* same set of clauses; keep only the cheapest-to-scan of any such groups.
* The surviving paths are put into an array for qsort'ing.
*/
pathinfoarray = (PathClauseUsage **)
palloc(npaths * sizeof(PathClauseUsage *));
clauselist = NIL;
npaths = 0;
foreach(l, paths)
{
Path *ipath = (Path *) lfirst(l);
pathinfo = classify_index_clause_usage(ipath, &clauselist);
for (i = 0; i < npaths; i++)
{
if (bms_equal(pathinfo->clauseids, pathinfoarray[i]->clauseids))
break;
}
if (i < npaths)
{
/* duplicate clauseids, keep the cheaper one */
Cost ncost;
Cost ocost;
Selectivity nselec;
Selectivity oselec;
cost_bitmap_tree_node(pathinfo->path, &ncost, &nselec);
cost_bitmap_tree_node(pathinfoarray[i]->path, &ocost, &oselec);
if (ncost < ocost)
pathinfoarray[i] = pathinfo;
}
else
{
/* not duplicate clauseids, add to array */
pathinfoarray[npaths++] = pathinfo;
}
}
/* If only one surviving path, we're done */
if (npaths == 1)
return pathinfoarray[0]->path;
/* Sort the surviving paths by index access cost */
qsort(pathinfoarray, npaths, sizeof(PathClauseUsage *),
path_usage_comparator);
/*
* For each surviving index, consider it as an "AND group leader", and see
* whether adding on any of the later indexes results in an AND path with
* cheaper total cost than before. Then take the cheapest AND group.
*/
for (i = 0; i < npaths; i++)
{
Cost costsofar;
List *qualsofar;
Bitmapset *clauseidsofar;
ListCell *lastcell;
pathinfo = pathinfoarray[i];
paths = list_make1(pathinfo->path);
costsofar = bitmap_scan_cost_est(root, rel, pathinfo->path);
qualsofar = list_concat(list_copy(pathinfo->quals),
list_copy(pathinfo->preds));
clauseidsofar = bms_copy(pathinfo->clauseids);
lastcell = list_head(paths); /* for quick deletions */
for (j = i + 1; j < npaths; j++)
{
Cost newcost;
pathinfo = pathinfoarray[j];
/* Check for redundancy */
if (bms_overlap(pathinfo->clauseids, clauseidsofar))
continue; /* consider it redundant */
if (pathinfo->preds)
{
bool redundant = false;
/* we check each predicate clause separately */
foreach(l, pathinfo->preds)
{
Node *np = (Node *) lfirst(l);
if (predicate_implied_by(list_make1(np), qualsofar))
{
redundant = true;
break; /* out of inner foreach loop */
}
}
if (redundant)
continue;
}
/* tentatively add new path to paths, so we can estimate cost */
paths = lappend(paths, pathinfo->path);
newcost = bitmap_and_cost_est(root, rel, paths);
if (newcost < costsofar)
{
/* keep new path in paths, update subsidiary variables */
costsofar = newcost;
qualsofar = list_concat(qualsofar,
list_copy(pathinfo->quals));
qualsofar = list_concat(qualsofar,
list_copy(pathinfo->preds));
clauseidsofar = bms_add_members(clauseidsofar,
pathinfo->clauseids);
lastcell = lnext(lastcell);
}
else
{
/* reject new path, remove it from paths list */
paths = list_delete_cell(paths, lnext(lastcell), lastcell);
}
Assert(lnext(lastcell) == NULL);
}
/* Keep the cheapest AND-group (or singleton) */
if (i == 0 || costsofar < bestcost)
{
bestpaths = paths;
bestcost = costsofar;
}
/* some easy cleanup (we don't try real hard though) */
list_free(qualsofar);
}
if (list_length(bestpaths) == 1)
return (Path *) linitial(bestpaths); /* no need for AND */
return (Path *) create_bitmap_and_path(root, rel, bestpaths);
}
/* qsort comparator to sort in increasing index access cost order */
static int
path_usage_comparator(const void *a, const void *b)
{
PathClauseUsage *pa = *(PathClauseUsage *const *) a;
PathClauseUsage *pb = *(PathClauseUsage *const *) b;
Cost acost;
Cost bcost;
Selectivity aselec;
Selectivity bselec;
cost_bitmap_tree_node(pa->path, &acost, &aselec);
cost_bitmap_tree_node(pb->path, &bcost, &bselec);
/*
* If costs are the same, sort by selectivity.
*/
if (acost < bcost)
return -1;
if (acost > bcost)
return 1;
if (aselec < bselec)
return -1;
if (aselec > bselec)
return 1;
return 0;
}
/*
* Estimate the cost of actually executing a bitmap scan with a single
* index path (no BitmapAnd, at least not at this level).
*/
static Cost
bitmap_scan_cost_est(PlannerInfo *root, RelOptInfo *rel, Path *ipath)
{
BitmapHeapPath bpath;
/* Set up a dummy BitmapHeapPath */
bpath.path.type = T_BitmapHeapPath;
bpath.path.pathtype = T_BitmapHeapScan;
bpath.path.parent = rel;
bpath.path.pathkeys = NIL;
bpath.path.required_outer = ipath->required_outer;
bpath.path.param_clauses = ipath->param_clauses;
bpath.bitmapqual = ipath;
cost_bitmap_heap_scan((Path *) &bpath, root, rel, ipath,
get_loop_count(root, bpath.path.required_outer));
return bpath.path.total_cost;
}
/*
* Estimate the cost of actually executing a BitmapAnd scan with the given
* inputs.
*/
static Cost
bitmap_and_cost_est(PlannerInfo *root, RelOptInfo *rel, List *paths)
{
BitmapAndPath *apath;
BitmapHeapPath bpath;
/*
* Create a temporary BitmapAndPath. (Because it needs realistic
* required_outer and param_clauses values, making a dummy one would
* take more code than it's worth.)
*/
apath = create_bitmap_and_path(root, rel, paths);
/* Set up a dummy BitmapHeapPath */
bpath.path.type = T_BitmapHeapPath;
bpath.path.pathtype = T_BitmapHeapScan;
bpath.path.parent = rel;
bpath.path.pathkeys = NIL;
bpath.path.required_outer = apath->path.required_outer;
bpath.path.param_clauses = apath->path.param_clauses;
bpath.bitmapqual = (Path *) apath;
/* Now we can do cost_bitmap_heap_scan */
cost_bitmap_heap_scan((Path *) &bpath, root, rel, (Path *) apath,
get_loop_count(root, bpath.path.required_outer));
return bpath.path.total_cost;
}
/*
* classify_index_clause_usage
* Construct a PathClauseUsage struct describing the WHERE clauses and
* index predicate clauses used by the given indexscan path.
* We consider two clauses the same if they are equal().
*
* At some point we might want to migrate this info into the Path data
* structure proper, but for the moment it's only needed within
* choose_bitmap_and().
*
* *clauselist is used and expanded as needed to identify all the distinct
* clauses seen across successive calls. Caller must initialize it to NIL
* before first call of a set.
*/
static PathClauseUsage *
classify_index_clause_usage(Path *path, List **clauselist)
{
PathClauseUsage *result;
Bitmapset *clauseids;
ListCell *lc;
result = (PathClauseUsage *) palloc(sizeof(PathClauseUsage));
result->path = path;
/* Recursively find the quals and preds used by the path */
result->quals = NIL;
result->preds = NIL;
find_indexpath_quals(path, &result->quals, &result->preds);
/* Build up a bitmapset representing the quals and preds */
clauseids = NULL;
foreach(lc, result->quals)
{
Node *node = (Node *) lfirst(lc);
clauseids = bms_add_member(clauseids,
find_list_position(node, clauselist));
}
foreach(lc, result->preds)
{
Node *node = (Node *) lfirst(lc);
clauseids = bms_add_member(clauseids,
find_list_position(node, clauselist));
}
result->clauseids = clauseids;
return result;
}
/*
* find_indexpath_quals
*
* Given the Path structure for a plain or bitmap indexscan, extract lists
* of all the indexquals and index predicate conditions used in the Path.
* These are appended to the initial contents of *quals and *preds (hence
* caller should initialize those to NIL).
*
* This is sort of a simplified version of make_restrictinfo_from_bitmapqual;
* here, we are not trying to produce an accurate representation of the AND/OR
* semantics of the Path, but just find out all the base conditions used.
*
* The result lists contain pointers to the expressions used in the Path,
* but all the list cells are freshly built, so it's safe to destructively
* modify the lists (eg, by concat'ing with other lists).
*/
static void
find_indexpath_quals(Path *bitmapqual, List **quals, List **preds)
{
if (IsA(bitmapqual, BitmapAndPath))
{
BitmapAndPath *apath = (BitmapAndPath *) bitmapqual;
ListCell *l;
foreach(l, apath->bitmapquals)
{
find_indexpath_quals((Path *) lfirst(l), quals, preds);
}
}
else if (IsA(bitmapqual, BitmapOrPath))
{
BitmapOrPath *opath = (BitmapOrPath *) bitmapqual;
ListCell *l;
foreach(l, opath->bitmapquals)
{
find_indexpath_quals((Path *) lfirst(l), quals, preds);
}
}
else if (IsA(bitmapqual, IndexPath))
{
IndexPath *ipath = (IndexPath *) bitmapqual;
*quals = list_concat(*quals, get_actual_clauses(ipath->indexclauses));
*preds = list_concat(*preds, list_copy(ipath->indexinfo->indpred));
}
else
elog(ERROR, "unrecognized node type: %d", nodeTag(bitmapqual));
}
/*
* find_list_position
* Return the given node's position (counting from 0) in the given
* list of nodes. If it's not equal() to any existing list member,
* add it at the end, and return that position.
*/
static int
find_list_position(Node *node, List **nodelist)
{
int i;
ListCell *lc;
i = 0;
foreach(lc, *nodelist)
{
Node *oldnode = (Node *) lfirst(lc);
if (equal(node, oldnode))
return i;
i++;
}
*nodelist = lappend(*nodelist, node);
return i;
}
/*
* check_index_only
* Determine whether an index-only scan is possible for this index.
*/
static bool
check_index_only(RelOptInfo *rel, IndexOptInfo *index)
{
bool result;
Bitmapset *attrs_used = NULL;
Bitmapset *index_attrs = NULL;
ListCell *lc;
int i;
/* Index-only scans must be enabled, and index must be capable of them */
if (!enable_indexonlyscan)
return false;
if (!index->canreturn)
return false;
/*
* Check that all needed attributes of the relation are available from
* the index.
*
* XXX this is overly conservative for partial indexes, since we will
* consider attributes involved in the index predicate as required even
* though the predicate won't need to be checked at runtime. (The same
* is true for attributes used only in index quals, if we are certain
* that the index is not lossy.) However, it would be quite expensive
* to determine that accurately at this point, so for now we take the
* easy way out.
*/
/*
* Add all the attributes needed for joins or final output. Note: we must
* look at reltargetlist, not the attr_needed data, because attr_needed
* isn't computed for inheritance child rels.
*/
pull_varattnos((Node *) rel->reltargetlist, rel->relid, &attrs_used);
/* Add all the attributes used by restriction clauses. */
foreach(lc, rel->baserestrictinfo)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
pull_varattnos((Node *) rinfo->clause, rel->relid, &attrs_used);
}
/* Construct a bitmapset of columns stored in the index. */
for (i = 0; i < index->ncolumns; i++)
{
int attno = index->indexkeys[i];
/*
* For the moment, we just ignore index expressions. It might be nice
* to do something with them, later.
*/
if (attno == 0)
continue;
index_attrs =
bms_add_member(index_attrs,
attno - FirstLowInvalidHeapAttributeNumber);
}
/* Do we have all the necessary attributes? */
result = bms_is_subset(attrs_used, index_attrs);
bms_free(attrs_used);
bms_free(index_attrs);
return result;
}
/*
* get_loop_count
* Choose the loop count estimate to use for costing a parameterized path
* with the given set of outer relids.
*
* Since we produce parameterized paths before we've begun to generate join
* relations, it's impossible to predict exactly how many times a parameterized
* path will be iterated; we don't know the size of the relation that will be
* on the outside of the nestloop. However, we should try to account for
* multiple iterations somehow in costing the path. The heuristic embodied
* here is to use the rowcount of the smallest other base relation needed in
* the join clauses used by the path. (We could alternatively consider the
* largest one, but that seems too optimistic.) This is of course the right
* answer for single-other-relation cases, and it seems like a reasonable
* zero-order approximation for multiway-join cases.
*
* Note: for this to work, allpaths.c must establish all baserel size
* estimates before it begins to compute paths, or at least before it
* calls create_index_paths().
*/
static double
get_loop_count(PlannerInfo *root, Relids outer_relids)
{
double result = 1.0;
/* For a non-parameterized path, just return 1.0 quickly */
if (outer_relids != NULL)
{
int relid;
/* Need a working copy since bms_first_member is destructive */
outer_relids = bms_copy(outer_relids);
while ((relid = bms_first_member(outer_relids)) >= 0)
{
RelOptInfo *outer_rel;
/* Paranoia: ignore bogus relid indexes */
if (relid >= root->simple_rel_array_size)
continue;
outer_rel = root->simple_rel_array[relid];
if (outer_rel == NULL)
continue;
Assert(outer_rel->relid == relid); /* sanity check on array */
/* Other relation could be proven empty, if so ignore */
if (IS_DUMMY_REL(outer_rel))
continue;
/* Otherwise, rel's rows estimate should be valid by now */
Assert(outer_rel->rows > 0);
/* Remember smallest row count estimate among the outer rels */
if (result == 1.0 || result > outer_rel->rows)
result = outer_rel->rows;
}
bms_free(outer_relids);
}
return result;
}
/****************************************************************************
* ---- ROUTINES TO CHECK QUERY CLAUSES ----
****************************************************************************/
/*
* match_restriction_clauses_to_index
* Identify restriction clauses for the rel that match the index.
* Matching clauses are added to *clauseset.
*/
static void
match_restriction_clauses_to_index(RelOptInfo *rel, IndexOptInfo *index,
IndexClauseSet *clauseset)
{
match_clauses_to_index(index, rel->baserestrictinfo, clauseset);
}
/*
* match_join_clauses_to_index
* Identify join clauses for the rel that match the index.
* Matching clauses are added to *clauseset.
* Also, add any potentially usable join OR clauses to *joinorclauses.
*/
static void
match_join_clauses_to_index(PlannerInfo *root,
RelOptInfo *rel, IndexOptInfo *index,
IndexClauseSet *clauseset,
List **joinorclauses)
{
Relids inner_baserels;
ListCell *lc;
/*
* There is no value in considering join clauses for outer joins in which
* the indexed relation is on the outside, since there'd be no way to
* perform such a join with a parameterized nestloop. So first, identify
* all baserels that are on the inside of such joins.
*/
inner_baserels = NULL;
foreach(lc, root->join_info_list)
{
SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(lc);
if (bms_overlap(rel->relids, sjinfo->min_lefthand))
inner_baserels = bms_add_members(inner_baserels,
sjinfo->min_righthand);
/* full joins constrain both sides symmetrically */
if (sjinfo->jointype == JOIN_FULL &&
bms_overlap(rel->relids, sjinfo->min_righthand))
inner_baserels = bms_add_members(inner_baserels,
sjinfo->min_lefthand);
}
/* Now scan the rel's join clauses */
foreach(lc, rel->joininfo)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
/* Ignore if it mentions anything from wrong side of an outer join */
if (bms_overlap(rinfo->clause_relids, inner_baserels))
continue;
/*
* Note that we ignore required_relids; that's okay because we are
* intentionally ignoring the normal rules for placing evaluation of
* join clauses. The whole point here is to evaluate join clauses
* below their join, even if they would normally be delayed by
* outer join rules.
*
* Instead of considering required_relids, we ignore clauses for which
* any referenced rel is in nullable_relids; that means there's an
* outer join below the clause and so it can't be checked at the
* relation scan level.
*
* Note: unlike create_or_index_quals(), we can accept clauses that
* are marked !is_pushed_down (ie they are themselves outer-join
* clauses). This is OK because any path generated with these clauses
* could only be used in the inside of a nestloop join, which will be
* the nullable side.
*/
if (bms_overlap(rinfo->clause_relids, rinfo->nullable_relids))
continue;
/* Potentially usable, so see if it matches the index or is an OR */
if (restriction_is_or_clause(rinfo))
*joinorclauses = lappend(*joinorclauses, rinfo);
else
match_clause_to_index(index, rinfo, clauseset);
}
}
/*
* match_eclass_clauses_to_index
* Identify EquivalenceClass join clauses for the rel that match the index.
* Matching clauses are added to *clauseset.
*/
static void
match_eclass_clauses_to_index(PlannerInfo *root, IndexOptInfo *index,
IndexClauseSet *clauseset)
{
int indexcol;
/* No work if rel is not in any such ECs */
if (!index->rel->has_eclass_joins)
return;
for (indexcol = 0; indexcol < index->ncolumns; indexcol++)
{
List *clauses;
clauses = generate_implied_equalities_for_indexcol(root,
index,
indexcol);
/*
* We have to check whether the results actually do match the index,
* since for non-btree indexes the EC's equality operators might not
* be in the index opclass (cf eclass_member_matches_indexcol).
*/
match_clauses_to_index(index, clauses, clauseset);
}
}
/*
* match_clauses_to_index
* Perform match_clause_to_index() for each clause in a list.
* Matching clauses are added to *clauseset.
*/
static void
match_clauses_to_index(IndexOptInfo *index,
List *clauses,
IndexClauseSet *clauseset)
{
ListCell *lc;
foreach(lc, clauses)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
Assert(IsA(rinfo, RestrictInfo));
match_clause_to_index(index, rinfo, clauseset);
}
}
/*
* match_clause_to_index
* Test whether a qual clause can be used with an index.
*
* If the clause is usable, add it to the appropriate list in *clauseset.
* *clauseset must be initialized to zeroes before first call.
*
* Note: in some circumstances we may find the same RestrictInfos coming from
* multiple places. Defend against redundant outputs by refusing to add a
* clause twice (pointer equality should be a good enough check for this).
*
* Note: it's possible that a badly-defined index could have multiple matching
* columns. We always select the first match if so; this avoids scenarios
* wherein we get an inflated idea of the index's selectivity by using the
* same clause multiple times with different index columns.
*/
static void
match_clause_to_index(IndexOptInfo *index,
RestrictInfo *rinfo,
IndexClauseSet *clauseset)
{
int indexcol;
for (indexcol = 0; indexcol < index->ncolumns; indexcol++)
{
if (match_clause_to_indexcol(index,
indexcol,
rinfo))
{
clauseset->indexclauses[indexcol] =
list_append_unique_ptr(clauseset->indexclauses[indexcol],
rinfo);
clauseset->nonempty = true;
return;
}
}
}
/*
* match_clause_to_indexcol()
* Determines whether a restriction clause matches a column of an index.
*
* To match an index normally, the clause:
*
* (1) must be in the form (indexkey op const) or (const op indexkey);
* and
* (2) must contain an operator which is in the same family as the index
* operator for this column, or is a "special" operator as recognized
* by match_special_index_operator();
* and
* (3) must match the collation of the index, if collation is relevant.
*
* Our definition of "const" is exceedingly liberal: we allow anything that
* doesn't involve a volatile function or a Var of the index's relation.
* In particular, Vars belonging to other relations of the query are
* accepted here, since a clause of that form can be used in a
* parameterized indexscan. It's the responsibility of higher code levels
* to manage restriction and join clauses appropriately.
*
* Note: we do need to check for Vars of the index's relation on the
* "const" side of the clause, since clauses like (a.f1 OP (b.f2 OP a.f3))
* are not processable by a parameterized indexscan on a.f1, whereas
* something like (a.f1 OP (b.f2 OP c.f3)) is.
*
* Presently, the executor can only deal with indexquals that have the
* indexkey on the left, so we can only use clauses that have the indexkey
* on the right if we can commute the clause to put the key on the left.
* We do not actually do the commuting here, but we check whether a
* suitable commutator operator is available.
*
* If the index has a collation, the clause must have the same collation.
* For collation-less indexes, we assume it doesn't matter; this is
* necessary for cases like "hstore ? text", wherein hstore's operators
* don't care about collation but the clause will get marked with a
* collation anyway because of the text argument. (This logic is
* embodied in the macro IndexCollMatchesExprColl.)
*
* It is also possible to match RowCompareExpr clauses to indexes (but
* currently, only btree indexes handle this). In this routine we will
* report a match if the first column of the row comparison matches the
* target index column. This is sufficient to guarantee that some index
* condition can be constructed from the RowCompareExpr --- whether the
* remaining columns match the index too is considered in
* adjust_rowcompare_for_index().
*
* It is also possible to match ScalarArrayOpExpr clauses to indexes, when
* the clause is of the form "indexkey op ANY (arrayconst)".
*
* For boolean indexes, it is also possible to match the clause directly
* to the indexkey; or perhaps the clause is (NOT indexkey).
*
* 'index' is the index of interest.
* 'indexcol' is a column number of 'index' (counting from 0).
* 'rinfo' is the clause to be tested (as a RestrictInfo node).
*
* Returns true if the clause can be used with this index key.
*
* NOTE: returns false if clause is an OR or AND clause; it is the
* responsibility of higher-level routines to cope with those.
*/
static bool
match_clause_to_indexcol(IndexOptInfo *index,
int indexcol,
RestrictInfo *rinfo)
{
Expr *clause = rinfo->clause;
Index index_relid = index->rel->relid;
Oid opfamily = index->opfamily[indexcol];
Oid idxcollation = index->indexcollations[indexcol];
Node *leftop,
*rightop;
Relids left_relids;
Relids right_relids;
Oid expr_op;
Oid expr_coll;
bool plain_op;
/*
* Never match pseudoconstants to indexes. (Normally this could not
* happen anyway, since a pseudoconstant clause couldn't contain a Var,
* but what if someone builds an expression index on a constant? It's not
* totally unreasonable to do so with a partial index, either.)
*/
if (rinfo->pseudoconstant)
return false;
/* First check for boolean-index cases. */
if (IsBooleanOpfamily(opfamily))
{
if (match_boolean_index_clause((Node *) clause, indexcol, index))
return true;
}
/*
* Clause must be a binary opclause, or possibly a ScalarArrayOpExpr
* (which is always binary, by definition). Or it could be a
* RowCompareExpr, which we pass off to match_rowcompare_to_indexcol().
* Or, if the index supports it, we can handle IS NULL/NOT NULL clauses.
*/
if (is_opclause(clause))
{
leftop = get_leftop(clause);
rightop = get_rightop(clause);
if (!leftop || !rightop)
return false;
left_relids = rinfo->left_relids;
right_relids = rinfo->right_relids;
expr_op = ((OpExpr *) clause)->opno;
expr_coll = ((OpExpr *) clause)->inputcollid;
plain_op = true;
}
else if (clause && IsA(clause, ScalarArrayOpExpr))
{
ScalarArrayOpExpr *saop = (ScalarArrayOpExpr *) clause;
/* We only accept ANY clauses, not ALL */
if (!saop->useOr)
return false;
leftop = (Node *) linitial(saop->args);
rightop = (Node *) lsecond(saop->args);
left_relids = NULL; /* not actually needed */
right_relids = pull_varnos(rightop);
expr_op = saop->opno;
expr_coll = saop->inputcollid;
plain_op = false;
}
else if (clause && IsA(clause, RowCompareExpr))
{
return match_rowcompare_to_indexcol(index, indexcol,
opfamily, idxcollation,
(RowCompareExpr *) clause);
}
else if (index->amsearchnulls && IsA(clause, NullTest))
{
NullTest *nt = (NullTest *) clause;
if (!nt->argisrow &&
match_index_to_operand((Node *) nt->arg, indexcol, index))
return true;
return false;
}
else
return false;
/*
* Check for clauses of the form: (indexkey operator constant) or
* (constant operator indexkey). See above notes about const-ness.
*/
if (match_index_to_operand(leftop, indexcol, index) &&
!bms_is_member(index_relid, right_relids) &&
!contain_volatile_functions(rightop))
{
if (IndexCollMatchesExprColl(idxcollation, expr_coll) &&
is_indexable_operator(expr_op, opfamily, true))
return true;
/*
* If we didn't find a member of the index's opfamily, see whether it
* is a "special" indexable operator.
*/
if (plain_op &&
match_special_index_operator(clause, opfamily,
idxcollation, true))
return true;
return false;
}
if (plain_op &&
match_index_to_operand(rightop, indexcol, index) &&
!bms_is_member(index_relid, left_relids) &&
!contain_volatile_functions(leftop))
{
if (IndexCollMatchesExprColl(idxcollation, expr_coll) &&
is_indexable_operator(expr_op, opfamily, false))
return true;
/*
* If we didn't find a member of the index's opfamily, see whether it
* is a "special" indexable operator.
*/
if (match_special_index_operator(clause, opfamily,
idxcollation, false))
return true;
return false;
}
return false;
}
/*
* is_indexable_operator
* Does the operator match the specified index opfamily?
*
* If the indexkey is on the right, what we actually want to know
* is whether the operator has a commutator operator that matches
* the opfamily.
*/
static bool
is_indexable_operator(Oid expr_op, Oid opfamily, bool indexkey_on_left)
{
/* Get the commuted operator if necessary */
if (!indexkey_on_left)
{
expr_op = get_commutator(expr_op);
if (expr_op == InvalidOid)
return false;
}
/* OK if the (commuted) operator is a member of the index's opfamily */
return op_in_opfamily(expr_op, opfamily);
}
/*
* match_rowcompare_to_indexcol()
* Handles the RowCompareExpr case for match_clause_to_indexcol(),
* which see for comments.
*/
static bool
match_rowcompare_to_indexcol(IndexOptInfo *index,
int indexcol,
Oid opfamily,
Oid idxcollation,
RowCompareExpr *clause)
{
Index index_relid = index->rel->relid;
Node *leftop,
*rightop;
Oid expr_op;
Oid expr_coll;
/* Forget it if we're not dealing with a btree index */
if (index->relam != BTREE_AM_OID)
return false;
/*
* We could do the matching on the basis of insisting that the opfamily
* shown in the RowCompareExpr be the same as the index column's opfamily,
* but that could fail in the presence of reverse-sort opfamilies: it'd be
* a matter of chance whether RowCompareExpr had picked the forward or
* reverse-sort family. So look only at the operator, and match if it is
* a member of the index's opfamily (after commutation, if the indexkey is
* on the right). We'll worry later about whether any additional
* operators are matchable to the index.
*/
leftop = (Node *) linitial(clause->largs);
rightop = (Node *) linitial(clause->rargs);
expr_op = linitial_oid(clause->opnos);
expr_coll = linitial_oid(clause->inputcollids);
/* Collations must match, if relevant */
if (!IndexCollMatchesExprColl(idxcollation, expr_coll))
return false;
/*
* These syntactic tests are the same as in match_clause_to_indexcol()
*/
if (match_index_to_operand(leftop, indexcol, index) &&
!bms_is_member(index_relid, pull_varnos(rightop)) &&
!contain_volatile_functions(rightop))
{
/* OK, indexkey is on left */
}
else if (match_index_to_operand(rightop, indexcol, index) &&
!bms_is_member(index_relid, pull_varnos(leftop)) &&
!contain_volatile_functions(leftop))
{
/* indexkey is on right, so commute the operator */
expr_op = get_commutator(expr_op);
if (expr_op == InvalidOid)
return false;
}
else
return false;
/* We're good if the operator is the right type of opfamily member */
switch (get_op_opfamily_strategy(expr_op, opfamily))
{
case BTLessStrategyNumber:
case BTLessEqualStrategyNumber:
case BTGreaterEqualStrategyNumber:
case BTGreaterStrategyNumber:
return true;
}
return false;
}
/****************************************************************************
* ---- ROUTINES TO CHECK ORDERING OPERATORS ----
****************************************************************************/
/*
* match_pathkeys_to_index
* Test whether an index can produce output ordered according to the
* given pathkeys using "ordering operators".
*
* If it can, return a list of suitable ORDER BY expressions, each of the form
* "indexedcol operator pseudoconstant", along with an integer list of the
* index column numbers (zero based) that each clause would be used with.
* NIL lists are returned if the ordering is not achievable this way.
*
* On success, the result list is ordered by pathkeys, and in fact is
* one-to-one with the requested pathkeys.
*/
static void
match_pathkeys_to_index(IndexOptInfo *index, List *pathkeys,
List **orderby_clauses_p,
List **clause_columns_p)
{
List *orderby_clauses = NIL;
List *clause_columns = NIL;
ListCell *lc1;
*orderby_clauses_p = NIL; /* set default results */
*clause_columns_p = NIL;
/* Only indexes with the amcanorderbyop property are interesting here */
if (!index->amcanorderbyop)
return;
foreach(lc1, pathkeys)
{
PathKey *pathkey = (PathKey *) lfirst(lc1);
bool found = false;
ListCell *lc2;
/*
* Note: for any failure to match, we just return NIL immediately.
* There is no value in matching just some of the pathkeys.
*/
/* Pathkey must request default sort order for the target opfamily */
if (pathkey->pk_strategy != BTLessStrategyNumber ||
pathkey->pk_nulls_first)
return;
/* If eclass is volatile, no hope of using an indexscan */
if (pathkey->pk_eclass->ec_has_volatile)
return;
/* Try to match eclass member expression(s) to index */
foreach(lc2, pathkey->pk_eclass->ec_members)
{
EquivalenceMember *member = (EquivalenceMember *) lfirst(lc2);
int indexcol;
/* No possibility of match if it references other relations */
if (!bms_equal(member->em_relids, index->rel->relids))
continue;
for (indexcol = 0; indexcol < index->ncolumns; indexcol++)
{
Expr *expr;
expr = match_clause_to_ordering_op(index,
indexcol,
member->em_expr,
pathkey->pk_opfamily);
if (expr)
{
orderby_clauses = lappend(orderby_clauses, expr);
clause_columns = lappend_int(clause_columns, indexcol);
found = true;
break;
}
}
if (found) /* don't want to look at remaining members */
break;
}
if (!found) /* fail if no match for this pathkey */
return;
}
*orderby_clauses_p = orderby_clauses; /* success! */
*clause_columns_p = clause_columns;
}
/*
* match_clause_to_ordering_op
* Determines whether an ordering operator expression matches an
* index column.
*
* This is similar to, but simpler than, match_clause_to_indexcol.
* We only care about simple OpExpr cases. The input is a bare
* expression that is being ordered by, which must be of the form
* (indexkey op const) or (const op indexkey) where op is an ordering
* operator for the column's opfamily.
*
* 'index' is the index of interest.
* 'indexcol' is a column number of 'index' (counting from 0).
* 'clause' is the ordering expression to be tested.
* 'pk_opfamily' is the btree opfamily describing the required sort order.
*
* Note that we currently do not consider the collation of the ordering
* operator's result. In practical cases the result type will be numeric
* and thus have no collation, and it's not very clear what to match to
* if it did have a collation. The index's collation should match the
* ordering operator's input collation, not its result.
*
* If successful, return 'clause' as-is if the indexkey is on the left,
* otherwise a commuted copy of 'clause'. If no match, return NULL.
*/
static Expr *
match_clause_to_ordering_op(IndexOptInfo *index,
int indexcol,
Expr *clause,
Oid pk_opfamily)
{
Oid opfamily = index->opfamily[indexcol];
Oid idxcollation = index->indexcollations[indexcol];
Node *leftop,
*rightop;
Oid expr_op;
Oid expr_coll;
Oid sortfamily;
bool commuted;
/*
* Clause must be a binary opclause.
*/
if (!is_opclause(clause))
return NULL;
leftop = get_leftop(clause);
rightop = get_rightop(clause);
if (!leftop || !rightop)
return NULL;
expr_op = ((OpExpr *) clause)->opno;
expr_coll = ((OpExpr *) clause)->inputcollid;
/*
* We can forget the whole thing right away if wrong collation.
*/
if (!IndexCollMatchesExprColl(idxcollation, expr_coll))
return NULL;
/*
* Check for clauses of the form: (indexkey operator constant) or
* (constant operator indexkey).
*/
if (match_index_to_operand(leftop, indexcol, index) &&
!contain_var_clause(rightop) &&
!contain_volatile_functions(rightop))
{
commuted = false;
}
else if (match_index_to_operand(rightop, indexcol, index) &&
!contain_var_clause(leftop) &&
!contain_volatile_functions(leftop))
{
/* Might match, but we need a commuted operator */
expr_op = get_commutator(expr_op);
if (expr_op == InvalidOid)
return NULL;
commuted = true;
}
else
return NULL;
/*
* Is the (commuted) operator an ordering operator for the opfamily? And
* if so, does it yield the right sorting semantics?
*/
sortfamily = get_op_opfamily_sortfamily(expr_op, opfamily);
if (sortfamily != pk_opfamily)
return NULL;
/* We have a match. Return clause or a commuted version thereof. */
if (commuted)
{
OpExpr *newclause = makeNode(OpExpr);
/* flat-copy all the fields of clause */
memcpy(newclause, clause, sizeof(OpExpr));
/* commute it */
newclause->opno = expr_op;
newclause->opfuncid = InvalidOid;
newclause->args = list_make2(rightop, leftop);
clause = (Expr *) newclause;
}
return clause;
}
/****************************************************************************
* ---- ROUTINES TO DO PARTIAL INDEX PREDICATE TESTS ----
****************************************************************************/
/*
* check_partial_indexes
* Check each partial index of the relation, and mark it predOK if
* the index's predicate is satisfied for this query.
*
* Note: it is possible for this to get re-run after adding more restrictions
* to the rel; so we might be able to prove more indexes OK. We assume that
* adding more restrictions can't make an index not OK.
*/
void
check_partial_indexes(PlannerInfo *root, RelOptInfo *rel)
{
List *restrictinfo_list = rel->baserestrictinfo;
ListCell *ilist;
foreach(ilist, rel->indexlist)
{
IndexOptInfo *index = (IndexOptInfo *) lfirst(ilist);
if (index->indpred == NIL)
continue; /* ignore non-partial indexes */
if (index->predOK)
continue; /* don't repeat work if already proven OK */
index->predOK = predicate_implied_by(index->indpred,
restrictinfo_list);
}
}
/****************************************************************************
* ---- ROUTINES TO CHECK EXTERNALLY-VISIBLE CONDITIONS ----
****************************************************************************/
/*
* eclass_member_matches_indexcol
* Test whether an EquivalenceClass member matches an index column.
*
* This is exported for use by generate_implied_equalities_for_indexcol.
*/
bool
eclass_member_matches_indexcol(EquivalenceClass *ec, EquivalenceMember *em,
IndexOptInfo *index, int indexcol)
{
Oid curFamily = index->opfamily[indexcol];
Oid curCollation = index->indexcollations[indexcol];
/*
* If it's a btree index, we can reject it if its opfamily isn't
* compatible with the EC, since no clause generated from the EC could be
* used with the index. For non-btree indexes, we can't easily tell
* whether clauses generated from the EC could be used with the index,
* so don't check the opfamily. This might mean we return "true" for a
* useless EC, so we have to recheck the results of
* generate_implied_equalities_for_indexcol; see
* match_eclass_clauses_to_index.
*/
if (index->relam == BTREE_AM_OID &&
!list_member_oid(ec->ec_opfamilies, curFamily))
return false;
/* We insist on collation match for all index types, though */
if (!IndexCollMatchesExprColl(curCollation, ec->ec_collation))
return false;
return match_index_to_operand((Node *) em->em_expr, indexcol, index);
}
/*
* relation_has_unique_index_for
* Determine whether the relation provably has at most one row satisfying
* a set of equality conditions, because the conditions constrain all
* columns of some unique index.
*
* The conditions can be represented in either or both of two ways:
* 1. A list of RestrictInfo nodes, where the caller has already determined
* that each condition is a mergejoinable equality with an expression in
* this relation on one side, and an expression not involving this relation
* on the other. The transient outer_is_left flag is used to identify which
* side we should look at: left side if outer_is_left is false, right side
* if it is true.
* 2. A list of expressions in this relation, and a corresponding list of
* equality operators. The caller must have already checked that the operators
* represent equality. (Note: the operators could be cross-type; the
* expressions should correspond to their RHS inputs.)
*
* The caller need only supply equality conditions arising from joins;
* this routine automatically adds in any usable baserestrictinfo clauses.
* (Note that the passed-in restrictlist will be destructively modified!)
*/
bool
relation_has_unique_index_for(PlannerInfo *root, RelOptInfo *rel,
List *restrictlist,
List *exprlist, List *oprlist)
{
ListCell *ic;
Assert(list_length(exprlist) == list_length(oprlist));
/* Short-circuit if no indexes... */
if (rel->indexlist == NIL)
return false;
/*
* Examine the rel's restriction clauses for usable var = const clauses
* that we can add to the restrictlist.
*/
foreach(ic, rel->baserestrictinfo)
{
RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(ic);
/*
* Note: can_join won't be set for a restriction clause, but
* mergeopfamilies will be if it has a mergejoinable operator and
* doesn't contain volatile functions.
*/
if (restrictinfo->mergeopfamilies == NIL)
continue; /* not mergejoinable */
/*
* The clause certainly doesn't refer to anything but the given rel.
* If either side is pseudoconstant then we can use it.
*/
if (bms_is_empty(restrictinfo->left_relids))
{
/* righthand side is inner */
restrictinfo->outer_is_left = true;
}
else if (bms_is_empty(restrictinfo->right_relids))
{
/* lefthand side is inner */
restrictinfo->outer_is_left = false;
}
else
continue;
/* OK, add to list */
restrictlist = lappend(restrictlist, restrictinfo);
}
/* Short-circuit the easy case */
if (restrictlist == NIL && exprlist == NIL)
return false;
/* Examine each index of the relation ... */
foreach(ic, rel->indexlist)
{
IndexOptInfo *ind = (IndexOptInfo *) lfirst(ic);
int c;
/*
* If the index is not unique, or not immediately enforced, or if it's
* a partial index that doesn't match the query, it's useless here.
*/
if (!ind->unique || !ind->immediate ||
(ind->indpred != NIL && !ind->predOK))
continue;
/*
* Try to find each index column in the lists of conditions. This is
* O(N^2) or worse, but we expect all the lists to be short.
*/
for (c = 0; c < ind->ncolumns; c++)
{
bool matched = false;
ListCell *lc;
ListCell *lc2;
foreach(lc, restrictlist)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
Node *rexpr;
/*
* The condition's equality operator must be a member of the
* index opfamily, else it is not asserting the right kind of
* equality behavior for this index. We check this first
* since it's probably cheaper than match_index_to_operand().
*/
if (!list_member_oid(rinfo->mergeopfamilies, ind->opfamily[c]))
continue;
/*
* XXX at some point we may need to check collations here too.
* For the moment we assume all collations reduce to the same
* notion of equality.
*/
/* OK, see if the condition operand matches the index key */
if (rinfo->outer_is_left)
rexpr = get_rightop(rinfo->clause);
else
rexpr = get_leftop(rinfo->clause);
if (match_index_to_operand(rexpr, c, ind))
{
matched = true; /* column is unique */
break;
}
}
if (matched)
continue;
forboth(lc, exprlist, lc2, oprlist)
{
Node *expr = (Node *) lfirst(lc);
Oid opr = lfirst_oid(lc2);
/* See if the expression matches the index key */
if (!match_index_to_operand(expr, c, ind))
continue;
/*
* The equality operator must be a member of the index
* opfamily, else it is not asserting the right kind of
* equality behavior for this index. We assume the caller
* determined it is an equality operator, so we don't need to
* check any more tightly than this.
*/
if (!op_in_opfamily(opr, ind->opfamily[c]))
continue;
/*
* XXX at some point we may need to check collations here too.
* For the moment we assume all collations reduce to the same
* notion of equality.
*/
matched = true; /* column is unique */
break;
}
if (!matched)
break; /* no match; this index doesn't help us */
}
/* Matched all columns of this index? */
if (c == ind->ncolumns)
return true;
}
return false;
}
/****************************************************************************
* ---- ROUTINES TO CHECK OPERANDS ----
****************************************************************************/
/*
* match_index_to_operand()
* Generalized test for a match between an index's key
* and the operand on one side of a restriction or join clause.
*
* operand: the nodetree to be compared to the index
* indexcol: the column number of the index (counting from 0)
* index: the index of interest
*
* Note that we aren't interested in collations here; the caller must check
* for a collation match, if it's dealing with an operator where that matters.
*
* This is exported for use in selfuncs.c.
*/
bool
match_index_to_operand(Node *operand,
int indexcol,
IndexOptInfo *index)
{
int indkey;
/*
* Ignore any PlaceHolderVar nodes above the operand. This is needed so
* that we can successfully use expression-index constraints pushed down
* through appendrels (UNION ALL). It's safe because a PlaceHolderVar
* appearing in a relation-scan-level expression is certainly a no-op.
*/
while (operand && IsA(operand, PlaceHolderVar))
operand = (Node *) ((PlaceHolderVar *) operand)->phexpr;
/*
* Ignore any RelabelType node above the operand. This is needed to be
* able to apply indexscanning in binary-compatible-operator cases. Note:
* we can assume there is at most one RelabelType node;
* eval_const_expressions() will have simplified if more than one.
*/
if (operand && IsA(operand, RelabelType))
operand = (Node *) ((RelabelType *) operand)->arg;
indkey = index->indexkeys[indexcol];
if (indkey != 0)
{
/*
* Simple index column; operand must be a matching Var.
*/
if (operand && IsA(operand, Var) &&
index->rel->relid == ((Var *) operand)->varno &&
indkey == ((Var *) operand)->varattno)
return true;
}
else
{
/*
* Index expression; find the correct expression. (This search could
* be avoided, at the cost of complicating all the callers of this
* routine; doesn't seem worth it.)
*/
ListCell *indexpr_item;
int i;
Node *indexkey;
indexpr_item = list_head(index->indexprs);
for (i = 0; i < indexcol; i++)
{
if (index->indexkeys[i] == 0)
{
if (indexpr_item == NULL)
elog(ERROR, "wrong number of index expressions");
indexpr_item = lnext(indexpr_item);
}
}
if (indexpr_item == NULL)
elog(ERROR, "wrong number of index expressions");
indexkey = (Node *) lfirst(indexpr_item);
/*
* Does it match the operand? Again, strip any relabeling.
*/
if (indexkey && IsA(indexkey, RelabelType))
indexkey = (Node *) ((RelabelType *) indexkey)->arg;
if (equal(indexkey, operand))
return true;
}
return false;
}
/****************************************************************************
* ---- ROUTINES FOR "SPECIAL" INDEXABLE OPERATORS ----
****************************************************************************/
/*
* These routines handle special optimization of operators that can be
* used with index scans even though they are not known to the executor's
* indexscan machinery. The key idea is that these operators allow us
* to derive approximate indexscan qual clauses, such that any tuples
* that pass the operator clause itself must also satisfy the simpler
* indexscan condition(s). Then we can use the indexscan machinery
* to avoid scanning as much of the table as we'd otherwise have to,
* while applying the original operator as a qpqual condition to ensure
* we deliver only the tuples we want. (In essence, we're using a regular
* index as if it were a lossy index.)
*
* An example of what we're doing is
* textfield LIKE 'abc%'
* from which we can generate the indexscanable conditions
* textfield >= 'abc' AND textfield < 'abd'
* which allow efficient scanning of an index on textfield.
* (In reality, character set and collation issues make the transformation
* from LIKE to indexscan limits rather harder than one might think ...
* but that's the basic idea.)
*
* Another thing that we do with this machinery is to provide special
* smarts for "boolean" indexes (that is, indexes on boolean columns
* that support boolean equality). We can transform a plain reference
* to the indexkey into "indexkey = true", or "NOT indexkey" into
* "indexkey = false", so as to make the expression indexable using the
* regular index operators. (As of Postgres 8.1, we must do this here
* because constant simplification does the reverse transformation;
* without this code there'd be no way to use such an index at all.)
*
* Three routines are provided here:
*
* match_special_index_operator() is just an auxiliary function for
* match_clause_to_indexcol(); after the latter fails to recognize a
* restriction opclause's operator as a member of an index's opfamily,
* it asks match_special_index_operator() whether the clause should be
* considered an indexqual anyway.
*
* match_boolean_index_clause() similarly detects clauses that can be
* converted into boolean equality operators.
*
* expand_indexqual_conditions() converts a list of RestrictInfo nodes
* (with implicit AND semantics across list elements) into a list of clauses
* that the executor can actually handle. For operators that are members of
* the index's opfamily this transformation is a no-op, but clauses recognized
* by match_special_index_operator() or match_boolean_index_clause() must be
* converted into one or more "regular" indexqual conditions.
*/
/*
* match_boolean_index_clause
* Recognize restriction clauses that can be matched to a boolean index.
*
* This should be called only when IsBooleanOpfamily() recognizes the
* index's operator family. We check to see if the clause matches the
* index's key.
*/
static bool
match_boolean_index_clause(Node *clause,
int indexcol,
IndexOptInfo *index)
{
/* Direct match? */
if (match_index_to_operand(clause, indexcol, index))
return true;
/* NOT clause? */
if (not_clause(clause))
{
if (match_index_to_operand((Node *) get_notclausearg((Expr *) clause),
indexcol, index))
return true;
}
/*
* Since we only consider clauses at top level of WHERE, we can convert
* indexkey IS TRUE and indexkey IS FALSE to index searches as well. The
* different meaning for NULL isn't important.
*/
else if (clause && IsA(clause, BooleanTest))
{
BooleanTest *btest = (BooleanTest *) clause;
if (btest->booltesttype == IS_TRUE ||
btest->booltesttype == IS_FALSE)
if (match_index_to_operand((Node *) btest->arg,
indexcol, index))
return true;
}
return false;
}
/*
* match_special_index_operator
* Recognize restriction clauses that can be used to generate
* additional indexscanable qualifications.
*
* The given clause is already known to be a binary opclause having
* the form (indexkey OP pseudoconst) or (pseudoconst OP indexkey),
* but the OP proved not to be one of the index's opfamily operators.
* Return 'true' if we can do something with it anyway.
*/
static bool
match_special_index_operator(Expr *clause, Oid opfamily, Oid idxcollation,
bool indexkey_on_left)
{
bool isIndexable = false;
Node *rightop;
Oid expr_op;
Oid expr_coll;
Const *patt;
Const *prefix = NULL;
Const *rest = NULL;
Pattern_Prefix_Status pstatus = Pattern_Prefix_None;
/*
* Currently, all known special operators require the indexkey on the
* left, but this test could be pushed into the switch statement if some
* are added that do not...
*/
if (!indexkey_on_left)
return false;
/* we know these will succeed */
rightop = get_rightop(clause);
expr_op = ((OpExpr *) clause)->opno;
expr_coll = ((OpExpr *) clause)->inputcollid;
/* again, required for all current special ops: */
if (!IsA(rightop, Const) ||
((Const *) rightop)->constisnull)
return false;
patt = (Const *) rightop;
switch (expr_op)
{
case OID_TEXT_LIKE_OP:
case OID_BPCHAR_LIKE_OP:
case OID_NAME_LIKE_OP:
/* the right-hand const is type text for all of these */
pstatus = pattern_fixed_prefix(patt, Pattern_Type_Like, expr_coll,
&prefix, &rest);
isIndexable = (pstatus != Pattern_Prefix_None);
break;
case OID_BYTEA_LIKE_OP:
pstatus = pattern_fixed_prefix(patt, Pattern_Type_Like, expr_coll,
&prefix, &rest);
isIndexable = (pstatus != Pattern_Prefix_None);
break;
case OID_TEXT_ICLIKE_OP:
case OID_BPCHAR_ICLIKE_OP:
case OID_NAME_ICLIKE_OP:
/* the right-hand const is type text for all of these */
pstatus = pattern_fixed_prefix(patt, Pattern_Type_Like_IC, expr_coll,
&prefix, &rest);
isIndexable = (pstatus != Pattern_Prefix_None);
break;
case OID_TEXT_REGEXEQ_OP:
case OID_BPCHAR_REGEXEQ_OP:
case OID_NAME_REGEXEQ_OP:
/* the right-hand const is type text for all of these */
pstatus = pattern_fixed_prefix(patt, Pattern_Type_Regex, expr_coll,
&prefix, &rest);
isIndexable = (pstatus != Pattern_Prefix_None);
break;
case OID_TEXT_ICREGEXEQ_OP:
case OID_BPCHAR_ICREGEXEQ_OP:
case OID_NAME_ICREGEXEQ_OP:
/* the right-hand const is type text for all of these */
pstatus = pattern_fixed_prefix(patt, Pattern_Type_Regex_IC, expr_coll,
&prefix, &rest);
isIndexable = (pstatus != Pattern_Prefix_None);
break;
case OID_INET_SUB_OP:
case OID_INET_SUBEQ_OP:
isIndexable = true;
break;
}
if (prefix)
{
pfree(DatumGetPointer(prefix->constvalue));
pfree(prefix);
}
/* done if the expression doesn't look indexable */
if (!isIndexable)
return false;
/*
* Must also check that index's opfamily supports the operators we will
* want to apply. (A hash index, for example, will not support ">=".)
* Currently, only btree and spgist support the operators we need.
*
* Note: actually, in the Pattern_Prefix_Exact case, we only need "=" so a
* hash index would work. Currently it doesn't seem worth checking for
* that, however.
*
* We insist on the opfamily being the specific one we expect, else we'd
* do the wrong thing if someone were to make a reverse-sort opfamily with
* the same operators.
*
* The non-pattern opclasses will not sort the way we need in most non-C
* locales. We can use such an index anyway for an exact match (simple
* equality), but not for prefix-match cases. Note that here we are
* looking at the index's collation, not the expression's collation --
* this test is *not* dependent on the LIKE/regex operator's collation.
*/
switch (expr_op)
{
case OID_TEXT_LIKE_OP:
case OID_TEXT_ICLIKE_OP:
case OID_TEXT_REGEXEQ_OP:
case OID_TEXT_ICREGEXEQ_OP:
isIndexable =
(opfamily == TEXT_PATTERN_BTREE_FAM_OID) ||
(opfamily == TEXT_SPGIST_FAM_OID) ||
(opfamily == TEXT_BTREE_FAM_OID &&
(pstatus == Pattern_Prefix_Exact ||
lc_collate_is_c(idxcollation)));
break;
case OID_BPCHAR_LIKE_OP:
case OID_BPCHAR_ICLIKE_OP:
case OID_BPCHAR_REGEXEQ_OP:
case OID_BPCHAR_ICREGEXEQ_OP:
isIndexable =
(opfamily == BPCHAR_PATTERN_BTREE_FAM_OID) ||
(opfamily == BPCHAR_BTREE_FAM_OID &&
(pstatus == Pattern_Prefix_Exact ||
lc_collate_is_c(idxcollation)));
break;
case OID_NAME_LIKE_OP:
case OID_NAME_ICLIKE_OP:
case OID_NAME_REGEXEQ_OP:
case OID_NAME_ICREGEXEQ_OP:
/* name uses locale-insensitive sorting */
isIndexable = (opfamily == NAME_BTREE_FAM_OID);
break;
case OID_BYTEA_LIKE_OP:
isIndexable = (opfamily == BYTEA_BTREE_FAM_OID);
break;
case OID_INET_SUB_OP:
case OID_INET_SUBEQ_OP:
isIndexable = (opfamily == NETWORK_BTREE_FAM_OID);
break;
}
return isIndexable;
}
/*
* expand_indexqual_conditions
* Given a list of RestrictInfo nodes, produce a list of directly usable
* index qual clauses.
*
* Standard qual clauses (those in the index's opfamily) are passed through
* unchanged. Boolean clauses and "special" index operators are expanded
* into clauses that the indexscan machinery will know what to do with.
* RowCompare clauses are simplified if necessary to create a clause that is
* fully checkable by the index.
*
* In addition to the expressions themselves, there are auxiliary lists
* of the index column numbers that the clauses are meant to be used with;
* we generate an updated column number list for the result. (This is not
* the identical list because one input clause sometimes produces more than
* one output clause.)
*
* The input clauses are sorted by column number, and so the output is too.
* (This is depended on in various places in both planner and executor.)
*/
void
expand_indexqual_conditions(IndexOptInfo *index,
List *indexclauses, List *indexclausecols,
List **indexquals_p, List **indexqualcols_p)
{
List *indexquals = NIL;
List *indexqualcols = NIL;
ListCell *lcc,
*lci;
forboth(lcc, indexclauses, lci, indexclausecols)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lcc);
int indexcol = lfirst_int(lci);
Expr *clause = rinfo->clause;
Oid curFamily = index->opfamily[indexcol];
Oid curCollation = index->indexcollations[indexcol];
/* First check for boolean cases */
if (IsBooleanOpfamily(curFamily))
{
Expr *boolqual;
boolqual = expand_boolean_index_clause((Node *) clause,
indexcol,
index);
if (boolqual)
{
indexquals = lappend(indexquals,
make_simple_restrictinfo(boolqual));
indexqualcols = lappend_int(indexqualcols, indexcol);
continue;
}
}
/*
* Else it must be an opclause (usual case), ScalarArrayOp,
* RowCompare, or NullTest
*/
if (is_opclause(clause))
{
indexquals = list_concat(indexquals,
expand_indexqual_opclause(rinfo,
curFamily,
curCollation));
/* expand_indexqual_opclause can produce multiple clauses */
while (list_length(indexqualcols) < list_length(indexquals))
indexqualcols = lappend_int(indexqualcols, indexcol);
}
else if (IsA(clause, ScalarArrayOpExpr))
{
/* no extra work at this time */
indexquals = lappend(indexquals, rinfo);
indexqualcols = lappend_int(indexqualcols, indexcol);
}
else if (IsA(clause, RowCompareExpr))
{
indexquals = lappend(indexquals,
expand_indexqual_rowcompare(rinfo,
index,
indexcol));
indexqualcols = lappend_int(indexqualcols, indexcol);
}
else if (IsA(clause, NullTest))
{
Assert(index->amsearchnulls);
indexquals = lappend(indexquals, rinfo);
indexqualcols = lappend_int(indexqualcols, indexcol);
}
else
elog(ERROR, "unsupported indexqual type: %d",
(int) nodeTag(clause));
}
*indexquals_p = indexquals;
*indexqualcols_p = indexqualcols;
}
/*
* expand_boolean_index_clause
* Convert a clause recognized by match_boolean_index_clause into
* a boolean equality operator clause.
*
* Returns NULL if the clause isn't a boolean index qual.
*/
static Expr *
expand_boolean_index_clause(Node *clause,
int indexcol,
IndexOptInfo *index)
{
/* Direct match? */
if (match_index_to_operand(clause, indexcol, index))
{
/* convert to indexkey = TRUE */
return make_opclause(BooleanEqualOperator, BOOLOID, false,
(Expr *) clause,
(Expr *) makeBoolConst(true, false),
InvalidOid, InvalidOid);
}
/* NOT clause? */
if (not_clause(clause))
{
Node *arg = (Node *) get_notclausearg((Expr *) clause);
/* It must have matched the indexkey */
Assert(match_index_to_operand(arg, indexcol, index));
/* convert to indexkey = FALSE */
return make_opclause(BooleanEqualOperator, BOOLOID, false,
(Expr *) arg,
(Expr *) makeBoolConst(false, false),
InvalidOid, InvalidOid);
}
if (clause && IsA(clause, BooleanTest))
{
BooleanTest *btest = (BooleanTest *) clause;
Node *arg = (Node *) btest->arg;
/* It must have matched the indexkey */
Assert(match_index_to_operand(arg, indexcol, index));
if (btest->booltesttype == IS_TRUE)
{
/* convert to indexkey = TRUE */
return make_opclause(BooleanEqualOperator, BOOLOID, false,
(Expr *) arg,
(Expr *) makeBoolConst(true, false),
InvalidOid, InvalidOid);
}
if (btest->booltesttype == IS_FALSE)
{
/* convert to indexkey = FALSE */
return make_opclause(BooleanEqualOperator, BOOLOID, false,
(Expr *) arg,
(Expr *) makeBoolConst(false, false),
InvalidOid, InvalidOid);
}
/* Oops */
Assert(false);
}
return NULL;
}
/*
* expand_indexqual_opclause --- expand a single indexqual condition
* that is an operator clause
*
* The input is a single RestrictInfo, the output a list of RestrictInfos.
*
* In the base case this is just list_make1(), but we have to be prepared to
* expand special cases that were accepted by match_special_index_operator().
*/
static List *
expand_indexqual_opclause(RestrictInfo *rinfo, Oid opfamily, Oid idxcollation)
{
Expr *clause = rinfo->clause;
/* we know these will succeed */
Node *leftop = get_leftop(clause);
Node *rightop = get_rightop(clause);
Oid expr_op = ((OpExpr *) clause)->opno;
Oid expr_coll = ((OpExpr *) clause)->inputcollid;
Const *patt = (Const *) rightop;
Const *prefix = NULL;
Const *rest = NULL;
Pattern_Prefix_Status pstatus;
/*
* LIKE and regex operators are not members of any btree index opfamily,
* but they can be members of opfamilies for more exotic index types such
* as GIN. Therefore, we should only do expansion if the operator is
* actually not in the opfamily. But checking that requires a syscache
* lookup, so it's best to first see if the operator is one we are
* interested in.
*/
switch (expr_op)
{
case OID_TEXT_LIKE_OP:
case OID_BPCHAR_LIKE_OP:
case OID_NAME_LIKE_OP:
case OID_BYTEA_LIKE_OP:
if (!op_in_opfamily(expr_op, opfamily))
{
pstatus = pattern_fixed_prefix(patt, Pattern_Type_Like, expr_coll,
&prefix, &rest);
return prefix_quals(leftop, opfamily, idxcollation, prefix, pstatus);
}
break;
case OID_TEXT_ICLIKE_OP:
case OID_BPCHAR_ICLIKE_OP:
case OID_NAME_ICLIKE_OP:
if (!op_in_opfamily(expr_op, opfamily))
{
/* the right-hand const is type text for all of these */
pstatus = pattern_fixed_prefix(patt, Pattern_Type_Like_IC, expr_coll,
&prefix, &rest);
return prefix_quals(leftop, opfamily, idxcollation, prefix, pstatus);
}
break;
case OID_TEXT_REGEXEQ_OP:
case OID_BPCHAR_REGEXEQ_OP:
case OID_NAME_REGEXEQ_OP:
if (!op_in_opfamily(expr_op, opfamily))
{
/* the right-hand const is type text for all of these */
pstatus = pattern_fixed_prefix(patt, Pattern_Type_Regex, expr_coll,
&prefix, &rest);
return prefix_quals(leftop, opfamily, idxcollation, prefix, pstatus);
}
break;
case OID_TEXT_ICREGEXEQ_OP:
case OID_BPCHAR_ICREGEXEQ_OP:
case OID_NAME_ICREGEXEQ_OP:
if (!op_in_opfamily(expr_op, opfamily))
{
/* the right-hand const is type text for all of these */
pstatus = pattern_fixed_prefix(patt, Pattern_Type_Regex_IC, expr_coll,
&prefix, &rest);
return prefix_quals(leftop, opfamily, idxcollation, prefix, pstatus);
}
break;
case OID_INET_SUB_OP:
case OID_INET_SUBEQ_OP:
if (!op_in_opfamily(expr_op, opfamily))
{
return network_prefix_quals(leftop, expr_op, opfamily,
patt->constvalue);
}
break;
}
/* Default case: just make a list of the unmodified indexqual */
return list_make1(rinfo);
}
/*
* expand_indexqual_rowcompare --- expand a single indexqual condition
* that is a RowCompareExpr
*
* This is a thin wrapper around adjust_rowcompare_for_index; we export the
* latter so that createplan.c can use it to re-discover which columns of the
* index are used by a row comparison indexqual.
*/
static RestrictInfo *
expand_indexqual_rowcompare(RestrictInfo *rinfo,
IndexOptInfo *index,
int indexcol)
{
RowCompareExpr *clause = (RowCompareExpr *) rinfo->clause;
Expr *newclause;
List *indexcolnos;
bool var_on_left;
newclause = adjust_rowcompare_for_index(clause,
index,
indexcol,
&indexcolnos,
&var_on_left);
/*
* If we didn't have to change the RowCompareExpr, return the original
* RestrictInfo.
*/
if (newclause == (Expr *) clause)
return rinfo;
/* Else we need a new RestrictInfo */
return make_simple_restrictinfo(newclause);
}
/*
* adjust_rowcompare_for_index --- expand a single indexqual condition
* that is a RowCompareExpr
*
* It's already known that the first column of the row comparison matches
* the specified column of the index. We can use additional columns of the
* row comparison as index qualifications, so long as they match the index
* in the "same direction", ie, the indexkeys are all on the same side of the
* clause and the operators are all the same-type members of the opfamilies.
* If all the columns of the RowCompareExpr match in this way, we just use it
* as-is. Otherwise, we build a shortened RowCompareExpr (if more than one
* column matches) or a simple OpExpr (if the first-column match is all
* there is). In these cases the modified clause is always "<=" or ">="
* even when the original was "<" or ">" --- this is necessary to match all
* the rows that could match the original. (We are essentially building a
* lossy version of the row comparison when we do this.)
*
* *indexcolnos receives an integer list of the index column numbers (zero
* based) used in the resulting expression. The reason we need to return
* that is that if the index is selected for use, createplan.c will need to
* call this again to extract that list. (This is a bit grotty, but row
* comparison indexquals aren't used enough to justify finding someplace to
* keep the information in the Path representation.) Since createplan.c
* also needs to know which side of the RowCompareExpr is the index side,
* we also return *var_on_left_p rather than re-deducing that there.
*/
Expr *
adjust_rowcompare_for_index(RowCompareExpr *clause,
IndexOptInfo *index,
int indexcol,
List **indexcolnos,
bool *var_on_left_p)
{
bool var_on_left;
int op_strategy;
Oid op_lefttype;
Oid op_righttype;
int matching_cols;
Oid expr_op;
List *opfamilies;
List *lefttypes;
List *righttypes;
List *new_ops;
ListCell *largs_cell;
ListCell *rargs_cell;
ListCell *opnos_cell;
ListCell *collids_cell;
/* We have to figure out (again) how the first col matches */
var_on_left = match_index_to_operand((Node *) linitial(clause->largs),
indexcol, index);
Assert(var_on_left ||
match_index_to_operand((Node *) linitial(clause->rargs),
indexcol, index));
*var_on_left_p = var_on_left;
expr_op = linitial_oid(clause->opnos);
if (!var_on_left)
expr_op = get_commutator(expr_op);
get_op_opfamily_properties(expr_op, index->opfamily[indexcol], false,
&op_strategy,
&op_lefttype,
&op_righttype);
/* Initialize returned list of which index columns are used */
*indexcolnos = list_make1_int(indexcol);
/* Build lists of the opfamilies and operator datatypes in case needed */
opfamilies = list_make1_oid(index->opfamily[indexcol]);
lefttypes = list_make1_oid(op_lefttype);
righttypes = list_make1_oid(op_righttype);
/*
* See how many of the remaining columns match some index column in the
* same way. As in match_clause_to_indexcol(), the "other" side of
* any potential index condition is OK as long as it doesn't use Vars from
* the indexed relation.
*/
matching_cols = 1;
largs_cell = lnext(list_head(clause->largs));
rargs_cell = lnext(list_head(clause->rargs));
opnos_cell = lnext(list_head(clause->opnos));
collids_cell = lnext(list_head(clause->inputcollids));
while (largs_cell != NULL)
{
Node *varop;
Node *constop;
int i;
expr_op = lfirst_oid(opnos_cell);
if (var_on_left)
{
varop = (Node *) lfirst(largs_cell);
constop = (Node *) lfirst(rargs_cell);
}
else
{
varop = (Node *) lfirst(rargs_cell);
constop = (Node *) lfirst(largs_cell);
/* indexkey is on right, so commute the operator */
expr_op = get_commutator(expr_op);
if (expr_op == InvalidOid)
break; /* operator is not usable */
}
if (bms_is_member(index->rel->relid, pull_varnos(constop)))
break; /* no good, Var on wrong side */
if (contain_volatile_functions(constop))
break; /* no good, volatile comparison value */
/*
* The Var side can match any column of the index.
*/
for (i = 0; i < index->ncolumns; i++)
{
if (match_index_to_operand(varop, i, index) &&
get_op_opfamily_strategy(expr_op,
index->opfamily[i]) == op_strategy &&
IndexCollMatchesExprColl(index->indexcollations[i],
lfirst_oid(collids_cell)))
break;
}
if (i >= index->ncolumns)
break; /* no match found */
/* Add column number to returned list */
*indexcolnos = lappend_int(*indexcolnos, i);
/* Add opfamily and datatypes to lists */
get_op_opfamily_properties(expr_op, index->opfamily[i], false,
&op_strategy,
&op_lefttype,
&op_righttype);
opfamilies = lappend_oid(opfamilies, index->opfamily[i]);
lefttypes = lappend_oid(lefttypes, op_lefttype);
righttypes = lappend_oid(righttypes, op_righttype);
/* This column matches, keep scanning */
matching_cols++;
largs_cell = lnext(largs_cell);
rargs_cell = lnext(rargs_cell);
opnos_cell = lnext(opnos_cell);
collids_cell = lnext(collids_cell);
}
/* Return clause as-is if it's all usable as index quals */
if (matching_cols == list_length(clause->opnos))
return (Expr *) clause;
/*
* We have to generate a subset rowcompare (possibly just one OpExpr). The
* painful part of this is changing < to <= or > to >=, so deal with that
* first.
*/
if (op_strategy == BTLessEqualStrategyNumber ||
op_strategy == BTGreaterEqualStrategyNumber)
{
/* easy, just use the same operators */
new_ops = list_truncate(list_copy(clause->opnos), matching_cols);
}
else
{
ListCell *opfamilies_cell;
ListCell *lefttypes_cell;
ListCell *righttypes_cell;
if (op_strategy == BTLessStrategyNumber)
op_strategy = BTLessEqualStrategyNumber;
else if (op_strategy == BTGreaterStrategyNumber)
op_strategy = BTGreaterEqualStrategyNumber;
else
elog(ERROR, "unexpected strategy number %d", op_strategy);
new_ops = NIL;
lefttypes_cell = list_head(lefttypes);
righttypes_cell = list_head(righttypes);
foreach(opfamilies_cell, opfamilies)
{
Oid opfam = lfirst_oid(opfamilies_cell);
Oid lefttype = lfirst_oid(lefttypes_cell);
Oid righttype = lfirst_oid(righttypes_cell);
expr_op = get_opfamily_member(opfam, lefttype, righttype,
op_strategy);
if (!OidIsValid(expr_op)) /* should not happen */
elog(ERROR, "could not find member %d(%u,%u) of opfamily %u",
op_strategy, lefttype, righttype, opfam);
if (!var_on_left)
{
expr_op = get_commutator(expr_op);
if (!OidIsValid(expr_op)) /* should not happen */
elog(ERROR, "could not find commutator of member %d(%u,%u) of opfamily %u",
op_strategy, lefttype, righttype, opfam);
}
new_ops = lappend_oid(new_ops, expr_op);
lefttypes_cell = lnext(lefttypes_cell);
righttypes_cell = lnext(righttypes_cell);
}
}
/* If we have more than one matching col, create a subset rowcompare */
if (matching_cols > 1)
{
RowCompareExpr *rc = makeNode(RowCompareExpr);
if (var_on_left)
rc->rctype = (RowCompareType) op_strategy;
else
rc->rctype = (op_strategy == BTLessEqualStrategyNumber) ?
ROWCOMPARE_GE : ROWCOMPARE_LE;
rc->opnos = new_ops;
rc->opfamilies = list_truncate(list_copy(clause->opfamilies),
matching_cols);
rc->inputcollids = list_truncate(list_copy(clause->inputcollids),
matching_cols);
rc->largs = list_truncate((List *) copyObject(clause->largs),
matching_cols);
rc->rargs = list_truncate((List *) copyObject(clause->rargs),
matching_cols);
return (Expr *) rc;
}
else
{
return make_opclause(linitial_oid(new_ops), BOOLOID, false,
copyObject(linitial(clause->largs)),
copyObject(linitial(clause->rargs)),
InvalidOid,
linitial_oid(clause->inputcollids));
}
}
/*
* Given a fixed prefix that all the "leftop" values must have,
* generate suitable indexqual condition(s). opfamily is the index
* operator family; we use it to deduce the appropriate comparison
* operators and operand datatypes. collation is the input collation to use.
*/
static List *
prefix_quals(Node *leftop, Oid opfamily, Oid collation,
Const *prefix_const, Pattern_Prefix_Status pstatus)
{
List *result;
Oid datatype;
Oid oproid;
Expr *expr;
FmgrInfo ltproc;
Const *greaterstr;
Assert(pstatus != Pattern_Prefix_None);
switch (opfamily)
{
case TEXT_BTREE_FAM_OID:
case TEXT_PATTERN_BTREE_FAM_OID:
case TEXT_SPGIST_FAM_OID:
datatype = TEXTOID;
break;
case BPCHAR_BTREE_FAM_OID:
case BPCHAR_PATTERN_BTREE_FAM_OID:
datatype = BPCHAROID;
break;
case NAME_BTREE_FAM_OID:
datatype = NAMEOID;
break;
case BYTEA_BTREE_FAM_OID:
datatype = BYTEAOID;
break;
default:
/* shouldn't get here */
elog(ERROR, "unexpected opfamily: %u", opfamily);
return NIL;
}
/*
* If necessary, coerce the prefix constant to the right type. The given
* prefix constant is either text or bytea type.
*/
if (prefix_const->consttype != datatype)
{
char *prefix;
switch (prefix_const->consttype)
{
case TEXTOID:
prefix = TextDatumGetCString(prefix_const->constvalue);
break;
case BYTEAOID:
prefix = DatumGetCString(DirectFunctionCall1(byteaout,
prefix_const->constvalue));
break;
default:
elog(ERROR, "unexpected const type: %u",
prefix_const->consttype);
return NIL;
}
prefix_const = string_to_const(prefix, datatype);
pfree(prefix);
}
/*
* If we found an exact-match pattern, generate an "=" indexqual.
*/
if (pstatus == Pattern_Prefix_Exact)
{
oproid = get_opfamily_member(opfamily, datatype, datatype,
BTEqualStrategyNumber);
if (oproid == InvalidOid)
elog(ERROR, "no = operator for opfamily %u", opfamily);
expr = make_opclause(oproid, BOOLOID, false,
(Expr *) leftop, (Expr *) prefix_const,
InvalidOid, collation);
result = list_make1(make_simple_restrictinfo(expr));
return result;
}
/*
* Otherwise, we have a nonempty required prefix of the values.
*
* We can always say "x >= prefix".
*/
oproid = get_opfamily_member(opfamily, datatype, datatype,
BTGreaterEqualStrategyNumber);
if (oproid == InvalidOid)
elog(ERROR, "no >= operator for opfamily %u", opfamily);
expr = make_opclause(oproid, BOOLOID, false,
(Expr *) leftop, (Expr *) prefix_const,
InvalidOid, collation);
result = list_make1(make_simple_restrictinfo(expr));
/*-------
* If we can create a string larger than the prefix, we can say
* "x < greaterstr". NB: we rely on make_greater_string() to generate
* a guaranteed-greater string, not just a probably-greater string.
* In general this is only guaranteed in C locale, so we'd better be
* using a C-locale index collation.
*-------
*/
oproid = get_opfamily_member(opfamily, datatype, datatype,
BTLessStrategyNumber);
if (oproid == InvalidOid)
elog(ERROR, "no < operator for opfamily %u", opfamily);
fmgr_info(get_opcode(oproid), &ltproc);
greaterstr = make_greater_string(prefix_const, &ltproc, collation);
if (greaterstr)
{
expr = make_opclause(oproid, BOOLOID, false,
(Expr *) leftop, (Expr *) greaterstr,
InvalidOid, collation);
result = lappend(result, make_simple_restrictinfo(expr));
}
return result;
}
/*
* Given a leftop and a rightop, and a inet-family sup/sub operator,
* generate suitable indexqual condition(s). expr_op is the original
* operator, and opfamily is the index opfamily.
*/
static List *
network_prefix_quals(Node *leftop, Oid expr_op, Oid opfamily, Datum rightop)
{
bool is_eq;
Oid datatype;
Oid opr1oid;
Oid opr2oid;
Datum opr1right;
Datum opr2right;
List *result;
Expr *expr;
switch (expr_op)
{
case OID_INET_SUB_OP:
datatype = INETOID;
is_eq = false;
break;
case OID_INET_SUBEQ_OP:
datatype = INETOID;
is_eq = true;
break;
default:
elog(ERROR, "unexpected operator: %u", expr_op);
return NIL;
}
/*
* create clause "key >= network_scan_first( rightop )", or ">" if the
* operator disallows equality.
*/
if (is_eq)
{
opr1oid = get_opfamily_member(opfamily, datatype, datatype,
BTGreaterEqualStrategyNumber);
if (opr1oid == InvalidOid)
elog(ERROR, "no >= operator for opfamily %u", opfamily);
}
else
{
opr1oid = get_opfamily_member(opfamily, datatype, datatype,
BTGreaterStrategyNumber);
if (opr1oid == InvalidOid)
elog(ERROR, "no > operator for opfamily %u", opfamily);
}
opr1right = network_scan_first(rightop);
expr = make_opclause(opr1oid, BOOLOID, false,
(Expr *) leftop,
(Expr *) makeConst(datatype, -1,
InvalidOid, /* not collatable */
-1, opr1right,
false, false),
InvalidOid, InvalidOid);
result = list_make1(make_simple_restrictinfo(expr));
/* create clause "key <= network_scan_last( rightop )" */
opr2oid = get_opfamily_member(opfamily, datatype, datatype,
BTLessEqualStrategyNumber);
if (opr2oid == InvalidOid)
elog(ERROR, "no <= operator for opfamily %u", opfamily);
opr2right = network_scan_last(rightop);
expr = make_opclause(opr2oid, BOOLOID, false,
(Expr *) leftop,
(Expr *) makeConst(datatype, -1,
InvalidOid, /* not collatable */
-1, opr2right,
false, false),
InvalidOid, InvalidOid);
result = lappend(result, make_simple_restrictinfo(expr));
return result;
}
/*
* Handy subroutines for match_special_index_operator() and friends.
*/
/*
* Generate a Datum of the appropriate type from a C string.
* Note that all of the supported types are pass-by-ref, so the
* returned value should be pfree'd if no longer needed.
*/
static Datum
string_to_datum(const char *str, Oid datatype)
{
/*
* We cheat a little by assuming that CStringGetTextDatum() will do for
* bpchar and varchar constants too...
*/
if (datatype == NAMEOID)
return DirectFunctionCall1(namein, CStringGetDatum(str));
else if (datatype == BYTEAOID)
return DirectFunctionCall1(byteain, CStringGetDatum(str));
else
return CStringGetTextDatum(str);
}
/*
* Generate a Const node of the appropriate type from a C string.
*/
static Const *
string_to_const(const char *str, Oid datatype)
{
Datum conval = string_to_datum(str, datatype);
Oid collation;
int constlen;
/*
* We only need to support a few datatypes here, so hard-wire properties
* instead of incurring the expense of catalog lookups.
*/
switch (datatype)
{
case TEXTOID:
case VARCHAROID:
case BPCHAROID:
collation = DEFAULT_COLLATION_OID;
constlen = -1;
break;
case NAMEOID:
collation = InvalidOid;
constlen = NAMEDATALEN;
break;
case BYTEAOID:
collation = InvalidOid;
constlen = -1;
break;
default:
elog(ERROR, "unexpected datatype in string_to_const: %u",
datatype);
return NULL;
}
return makeConst(datatype, -1, collation, constlen,
conval, false, false);
}
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