rdelaage
/
postgresql
mirror of https://git.postgresql.org/git/postgresql.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Fix bitmap AND/OR scans on the inside of a nestloop partition-wise join. 

reparameterize_path_by_child() failed to reparameterize BitmapAnd
and BitmapOr paths.  This matters only if such a path is chosen as
the inside of a nestloop partition-wise join, where we have to pass
in parameters from the outside of the nestloop.  If that did happen,
we generated a bad plan that would likely lead to crashes at execution.

This is not entirely reparameterize_path_by_child()'s fault though;
it's the victim of an ancient decision (my ancient decision, I think)
to not bother filling in param_info in BitmapAnd/Or path nodes.  That
caused the function to believe that such nodes and their children
contain no parameter references and so need not be processed.

In hindsight that decision looks pretty penny-wise and pound-foolish:
while it saves a few cycles during path node setup, we do commonly
need the information later.  In particular, by reversing the decision
and requiring valid param_info data in all nodes of a bitmap path
tree, we can get rid of indxpath.c's get_bitmap_tree_required_outer()
function, which computed the data on-demand.  It's not unlikely that
that nets out as a savings of cycles in many scenarios.  A couple
of other things in indxpath.c can be simplified as well.

While here, get rid of some cases in reparameterize_path_by_child()
that are visibly dead or useless, given that we only care about
reparameterizing paths that can be on the inside of a parameterized
nestloop.  This case reminds one of the maxim that untested code
probably does not work, so I'm unwilling to leave unreachable code
in this function.  (I did leave the T_Gather case in place even
though it's not reached in the regression tests.  It's not very
clear to me when the planner might prefer to put Gather below
rather than above a nestloop, but at least in principle the case
might be interesting.)

Per bug #16536, originally from Arne Roland but with a test case
by Andrew Gierth.  Back-patch to v11 where this code came in.

Discussion: https://postgr.es/m/16536-2213ee0b3aad41fd@postgresql.org
This commit is contained in:
Tom Lane 2020-07-14 18:56:49 -04:00
parent de8feb1f3a
commit 689696c711
4 changed files with 211 additions and 158 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

121
src/backend/optimizer/path/indxpath.c
View File

@ -122,7 +122,6 @@ static Cost bitmap_and_cost_est(PlannerInfo *root, RelOptInfo *rel,
List *paths);
static PathClauseUsage *classify_index_clause_usage(Path *path,
List **clauselist);
static Relids get_bitmap_tree_required_outer(Path *bitmapqual);
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);
@ -357,23 +356,16 @@ create_index_paths(PlannerInfo *root, RelOptInfo *rel)
*/
if (bitjoinpaths != NIL)
{
List *path_outer;
List *all_path_outers;
ListCell *lc;
/*
* path_outer holds the parameterization of each path in bitjoinpaths
* (to save recalculating that several times), while all_path_outers
* holds all distinct parameterization sets.
*/
path_outer = all_path_outers = NIL;
/* Identify each distinct parameterization seen in bitjoinpaths */
all_path_outers = NIL;
foreach(lc, bitjoinpaths)
{
Path *path = (Path *) lfirst(lc);
Relids required_outer;
Relids required_outer = PATH_REQ_OUTER(path);
required_outer = get_bitmap_tree_required_outer(path);
path_outer = lappend(path_outer, required_outer);
if (!bms_equal_any(required_outer, all_path_outers))
all_path_outers = lappend(all_path_outers, required_outer);
}
@ -388,16 +380,14 @@ create_index_paths(PlannerInfo *root, RelOptInfo *rel)
double loop_count;
BitmapHeapPath *bpath;
ListCell *lcp;
ListCell *lco;
/* Identify all the bitmap join paths needing no more than that */
this_path_set = NIL;
forboth(lcp, bitjoinpaths, lco, path_outer)
foreach(lcp, bitjoinpaths)
{
Path *path = (Path *) lfirst(lcp);
Relids p_outers = (Relids) lfirst(lco);
if (bms_is_subset(p_outers, max_outers))
if (bms_is_subset(PATH_REQ_OUTER(path), max_outers))
this_path_set = lappend(this_path_set, path);
}
@ -411,7 +401,7 @@ create_index_paths(PlannerInfo *root, RelOptInfo *rel)
bitmapqual = choose_bitmap_and(root, rel, this_path_set);
/* And push that path into the mix */
required_outer = get_bitmap_tree_required_outer(bitmapqual);
required_outer = PATH_REQ_OUTER(bitmapqual);
loop_count = get_loop_count(root, rel->relid, required_outer);
bpath = create_bitmap_heap_path(root, rel, bitmapqual,
required_outer, loop_count, 0);
@ -1601,25 +1591,19 @@ path_usage_comparator(const void *a, const void *b)
/*
* Estimate the cost of actually executing a bitmap scan with a single
* index path (no BitmapAnd, at least not at this level; but it could be
* a BitmapOr).
* index path (which could be a BitmapAnd or BitmapOr node).
*/
static Cost
bitmap_scan_cost_est(PlannerInfo *root, RelOptInfo *rel, Path *ipath)
{
BitmapHeapPath bpath;
Relids required_outer;
/* Identify required outer rels, in case it's a parameterized scan */
required_outer = get_bitmap_tree_required_outer(ipath);
/* Set up a dummy BitmapHeapPath */
bpath.path.type = T_BitmapHeapPath;
bpath.path.pathtype = T_BitmapHeapScan;
bpath.path.parent = rel;
bpath.path.pathtarget = rel->reltarget;
bpath.path.param_info = get_baserel_parampathinfo(root, rel,
required_outer);
bpath.path.param_info = ipath->param_info;
bpath.path.pathkeys = NIL;
bpath.bitmapqual = ipath;
@ -1628,10 +1612,13 @@ bitmap_scan_cost_est(PlannerInfo *root, RelOptInfo *rel, Path *ipath)
* Parallel bitmap heap path will be considered at later stage.
*/
bpath.path.parallel_workers = 0;
/* Now we can do cost_bitmap_heap_scan */
cost_bitmap_heap_scan(&bpath.path, root, rel,
bpath.path.param_info,
ipath,
get_loop_count(root, rel->relid, required_outer));
get_loop_count(root, rel->relid,
PATH_REQ_OUTER(ipath)));
return bpath.path.total_cost;
}
@ -1643,46 +1630,15 @@ bitmap_scan_cost_est(PlannerInfo *root, RelOptInfo *rel, Path *ipath)
static Cost
bitmap_and_cost_est(PlannerInfo *root, RelOptInfo *rel, List *paths)
{
BitmapAndPath apath;
BitmapHeapPath bpath;
Relids required_outer;
/* Set up a dummy BitmapAndPath */
apath.path.type = T_BitmapAndPath;
apath.path.pathtype = T_BitmapAnd;
apath.path.parent = rel;
apath.path.pathtarget = rel->reltarget;
apath.path.param_info = NULL; /* not used in bitmap trees */
apath.path.pathkeys = NIL;
apath.bitmapquals = paths;
cost_bitmap_and_node(&apath, root);
/* Identify required outer rels, in case it's a parameterized scan */
required_outer = get_bitmap_tree_required_outer((Path *) &apath);
/* Set up a dummy BitmapHeapPath */
bpath.path.type = T_BitmapHeapPath;
bpath.path.pathtype = T_BitmapHeapScan;
bpath.path.parent = rel;
bpath.path.pathtarget = rel->reltarget;
bpath.path.param_info = get_baserel_parampathinfo(root, rel,
required_outer);
bpath.path.pathkeys = NIL;
bpath.bitmapqual = (Path *) &apath;
BitmapAndPath *apath;
/*
* Check the cost of temporary path without considering parallelism.
* Parallel bitmap heap path will be considered at later stage.
* Might as well build a real BitmapAndPath here, as the work is slightly
* too complicated to be worth repeating just to save one palloc.
*/
bpath.path.parallel_workers = 0;
apath = create_bitmap_and_path(root, rel, paths);
/* Now we can do cost_bitmap_heap_scan */
cost_bitmap_heap_scan(&bpath.path, root, rel,
bpath.path.param_info,
(Path *) &apath,
get_loop_count(root, rel->relid, required_outer));
return bpath.path.total_cost;
return bitmap_scan_cost_est(root, rel, (Path *) apath);
}
@ -1753,49 +1709,6 @@ classify_index_clause_usage(Path *path, List **clauselist)
}
/*
* get_bitmap_tree_required_outer
* Find the required outer rels for a bitmap tree (index/and/or)
*
* We don't associate any particular parameterization with a BitmapAnd or
* BitmapOr node; however, the IndexPaths have parameterization info, in
* their capacity as standalone access paths. The parameterization required
* for the bitmap heap scan node is the union of rels referenced in the
* child IndexPaths.
*/
static Relids
get_bitmap_tree_required_outer(Path *bitmapqual)
{
Relids result = NULL;
ListCell *lc;
if (IsA(bitmapqual, IndexPath))
{
return bms_copy(PATH_REQ_OUTER(bitmapqual));
}
else if (IsA(bitmapqual, BitmapAndPath))
{
foreach(lc, ((BitmapAndPath *) bitmapqual)->bitmapquals)
{
result = bms_join(result,
get_bitmap_tree_required_outer((Path *) lfirst(lc)));
}
}
else if (IsA(bitmapqual, BitmapOrPath))
{
foreach(lc, ((BitmapOrPath *) bitmapqual)->bitmapquals)
{
result = bms_join(result,
get_bitmap_tree_required_outer((Path *) lfirst(lc)));
}
}
else
elog(ERROR, "unrecognized node type: %d", nodeTag(bitmapqual));
return result;
}
/*
* find_indexpath_quals
*

100
src/backend/optimizer/util/pathnode.c
View File

@ -1081,11 +1081,27 @@ create_bitmap_and_path(PlannerInfo *root,
List *bitmapquals)
{
BitmapAndPath *pathnode = makeNode(BitmapAndPath);
Relids required_outer = NULL;
ListCell *lc;
pathnode->path.pathtype = T_BitmapAnd;
pathnode->path.parent = rel;
pathnode->path.pathtarget = rel->reltarget;
pathnode->path.param_info = NULL; /* not used in bitmap trees */
/*
* Identify the required outer rels as the union of what the child paths
* depend on. (Alternatively, we could insist that the caller pass this
* in, but it's more convenient and reliable to compute it here.)
*/
foreach(lc, bitmapquals)
{
Path *bitmapqual = (Path *) lfirst(lc);
required_outer = bms_add_members(required_outer,
PATH_REQ_OUTER(bitmapqual));
}
pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
required_outer);
/*
* Currently, a BitmapHeapPath, BitmapAndPath, or BitmapOrPath will be
@ -1117,11 +1133,27 @@ create_bitmap_or_path(PlannerInfo *root,
List *bitmapquals)
{
BitmapOrPath *pathnode = makeNode(BitmapOrPath);
Relids required_outer = NULL;
ListCell *lc;
pathnode->path.pathtype = T_BitmapOr;
pathnode->path.parent = rel;
pathnode->path.pathtarget = rel->reltarget;
pathnode->path.param_info = NULL; /* not used in bitmap trees */
/*
* Identify the required outer rels as the union of what the child paths
* depend on. (Alternatively, we could insist that the caller pass this
* in, but it's more convenient and reliable to compute it here.)
*/
foreach(lc, bitmapquals)
{
Path *bitmapqual = (Path *) lfirst(lc);
required_outer = bms_add_members(required_outer,
PATH_REQ_OUTER(bitmapqual));
}
pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
required_outer);
/*
* Currently, a BitmapHeapPath, BitmapAndPath, or BitmapOrPath will be
@ -3885,7 +3917,18 @@ do { \
!bms_overlap(PATH_REQ_OUTER(path), child_rel->top_parent_relids))
return path;
/* Reparameterize a copy of given path. */
/*
* If possible, reparameterize the given path, making a copy.
*
* This function is currently only applied to the inner side of a nestloop
* join that is being partitioned by the partitionwise-join code. Hence,
* we need only support path types that plausibly arise in that context.
* (In particular, supporting sorted path types would be a waste of code
* and cycles: even if we translated them here, they'd just lose in
* subsequent cost comparisons.) If we do see an unsupported path type,
* that just means we won't be able to generate a partitionwise-join plan
* using that path type.
*/
switch (nodeTag(path))
{
case T_Path:
@ -3932,16 +3975,6 @@ do { \
}
break;
case T_TidPath:
{
TidPath *tpath;
FLAT_COPY_PATH(tpath, path, TidPath);
ADJUST_CHILD_ATTRS(tpath->tidquals);
new_path = (Path *) tpath;
}
break;
case T_ForeignPath:
{
ForeignPath *fpath;
@ -4032,37 +4065,6 @@ do { \
}
break;
case T_MergeAppendPath:
{
MergeAppendPath *mapath;
FLAT_COPY_PATH(mapath, path, MergeAppendPath);
REPARAMETERIZE_CHILD_PATH_LIST(mapath->subpaths);
new_path = (Path *) mapath;
}
break;
case T_MaterialPath:
{
MaterialPath *mpath;
FLAT_COPY_PATH(mpath, path, MaterialPath);
REPARAMETERIZE_CHILD_PATH(mpath->subpath);
new_path = (Path *) mpath;
}
break;
case T_UniquePath:
{
UniquePath *upath;
FLAT_COPY_PATH(upath, path, UniquePath);
REPARAMETERIZE_CHILD_PATH(upath->subpath);
ADJUST_CHILD_ATTRS(upath->uniq_exprs);
new_path = (Path *) upath;
}
break;
case T_GatherPath:
{
GatherPath *gpath;
@ -4073,16 +4075,6 @@ do { \
}
break;
case T_GatherMergePath:
{
GatherMergePath *gmpath;
FLAT_COPY_PATH(gmpath, path, GatherMergePath);
REPARAMETERIZE_CHILD_PATH(gmpath->subpath);
new_path = (Path *) gmpath;
}
break;
default:
/* We don't know how to reparameterize this path. */

104
src/test/regress/expected/partition_join.out
View File

@ -2165,6 +2165,110 @@ SELECT t1.a, t1.c, t2.b, t2.c FROM prt1_n t1 FULL JOIN prt1 t2 ON (t1.c = t2.c);
-> Seq Scan on prt1_n_p2 t1_2
(10 rows)
--
-- Test some other plan types in a partitionwise join (unfortunately,
-- we need larger tables to get the planner to choose these plan types)
--
create temp table prtx1 (a integer, b integer, c integer)
partition by range (a);
create temp table prtx1_1 partition of prtx1 for values from (1) to (11);
create temp table prtx1_2 partition of prtx1 for values from (11) to (21);
create temp table prtx1_3 partition of prtx1 for values from (21) to (31);
create temp table prtx2 (a integer, b integer, c integer)
partition by range (a);
create temp table prtx2_1 partition of prtx2 for values from (1) to (11);
create temp table prtx2_2 partition of prtx2 for values from (11) to (21);
create temp table prtx2_3 partition of prtx2 for values from (21) to (31);
insert into prtx1 select 1 + i%30, i, i
from generate_series(1,1000) i;
insert into prtx2 select 1 + i%30, i, i
from generate_series(1,500) i, generate_series(1,10) j;
create index on prtx2 (b);
create index on prtx2 (c);
analyze prtx1;
analyze prtx2;
explain (costs off)
select * from prtx1
where not exists (select 1 from prtx2
where prtx2.a=prtx1.a and prtx2.b=prtx1.b and prtx2.c=123)
and a<20 and c=120;
QUERY PLAN
-------------------------------------------------------------
Append
-> Nested Loop Anti Join
-> Seq Scan on prtx1_1
Filter: ((a < 20) AND (c = 120))
-> Bitmap Heap Scan on prtx2_1
Recheck Cond: ((b = prtx1_1.b) AND (c = 123))
Filter: (a = prtx1_1.a)
-> BitmapAnd
-> Bitmap Index Scan on prtx2_1_b_idx
Index Cond: (b = prtx1_1.b)
-> Bitmap Index Scan on prtx2_1_c_idx
Index Cond: (c = 123)
-> Nested Loop Anti Join
-> Seq Scan on prtx1_2
Filter: ((a < 20) AND (c = 120))
-> Bitmap Heap Scan on prtx2_2
Recheck Cond: ((b = prtx1_2.b) AND (c = 123))
Filter: (a = prtx1_2.a)
-> BitmapAnd
-> Bitmap Index Scan on prtx2_2_b_idx
Index Cond: (b = prtx1_2.b)
-> Bitmap Index Scan on prtx2_2_c_idx
Index Cond: (c = 123)
(23 rows)
select * from prtx1
where not exists (select 1 from prtx2
where prtx2.a=prtx1.a and prtx2.b=prtx1.b and prtx2.c=123)
and a<20 and c=120;
a | b | c
---+-----+-----
1 | 120 | 120
(1 row)
explain (costs off)
select * from prtx1
where not exists (select 1 from prtx2
where prtx2.a=prtx1.a and (prtx2.b=prtx1.b+1 or prtx2.c=99))
and a<20 and c=91;
QUERY PLAN
-----------------------------------------------------------------
Append
-> Nested Loop Anti Join
-> Seq Scan on prtx1_1
Filter: ((a < 20) AND (c = 91))
-> Bitmap Heap Scan on prtx2_1
Recheck Cond: ((b = (prtx1_1.b + 1)) OR (c = 99))
Filter: (a = prtx1_1.a)
-> BitmapOr
-> Bitmap Index Scan on prtx2_1_b_idx
Index Cond: (b = (prtx1_1.b + 1))
-> Bitmap Index Scan on prtx2_1_c_idx
Index Cond: (c = 99)
-> Nested Loop Anti Join
-> Seq Scan on prtx1_2
Filter: ((a < 20) AND (c = 91))
-> Bitmap Heap Scan on prtx2_2
Recheck Cond: ((b = (prtx1_2.b + 1)) OR (c = 99))
Filter: (a = prtx1_2.a)
-> BitmapOr
-> Bitmap Index Scan on prtx2_2_b_idx
Index Cond: (b = (prtx1_2.b + 1))
-> Bitmap Index Scan on prtx2_2_c_idx
Index Cond: (c = 99)
(23 rows)
select * from prtx1
where not exists (select 1 from prtx2
where prtx2.a=prtx1.a and (prtx2.b=prtx1.b+1 or prtx2.c=99))
and a<20 and c=91;
a | b | c
---+----+----
2 | 91 | 91
(1 row)
--
-- Test advanced partition-matching algorithm for partitioned join
--

44
src/test/regress/sql/partition_join.sql
View File

@ -463,6 +463,50 @@ SELECT t1.a, t1.c, t2.b, t2.c FROM prt1_n t1 JOIN prt2_n t2 ON (t1.c = t2.c) JOI
EXPLAIN (COSTS OFF)
SELECT t1.a, t1.c, t2.b, t2.c FROM prt1_n t1 FULL JOIN prt1 t2 ON (t1.c = t2.c);
--
-- Test some other plan types in a partitionwise join (unfortunately,
-- we need larger tables to get the planner to choose these plan types)
--
create temp table prtx1 (a integer, b integer, c integer)
partition by range (a);
create temp table prtx1_1 partition of prtx1 for values from (1) to (11);
create temp table prtx1_2 partition of prtx1 for values from (11) to (21);
create temp table prtx1_3 partition of prtx1 for values from (21) to (31);
create temp table prtx2 (a integer, b integer, c integer)
partition by range (a);
create temp table prtx2_1 partition of prtx2 for values from (1) to (11);
create temp table prtx2_2 partition of prtx2 for values from (11) to (21);
create temp table prtx2_3 partition of prtx2 for values from (21) to (31);
insert into prtx1 select 1 + i%30, i, i
from generate_series(1,1000) i;
insert into prtx2 select 1 + i%30, i, i
from generate_series(1,500) i, generate_series(1,10) j;
create index on prtx2 (b);
create index on prtx2 (c);
analyze prtx1;
analyze prtx2;
explain (costs off)
select * from prtx1
where not exists (select 1 from prtx2
where prtx2.a=prtx1.a and prtx2.b=prtx1.b and prtx2.c=123)
and a<20 and c=120;
select * from prtx1
where not exists (select 1 from prtx2
where prtx2.a=prtx1.a and prtx2.b=prtx1.b and prtx2.c=123)
and a<20 and c=120;
explain (costs off)
select * from prtx1
where not exists (select 1 from prtx2
where prtx2.a=prtx1.a and (prtx2.b=prtx1.b+1 or prtx2.c=99))
and a<20 and c=91;
select * from prtx1
where not exists (select 1 from prtx2
where prtx2.a=prtx1.a and (prtx2.b=prtx1.b+1 or prtx2.c=99))
and a<20 and c=91;
--
-- Test advanced partition-matching algorithm for partitioned join