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Reduce memory used by partitionwise joins

author Amit Langote <amitlan@postgresql.org>

2024年3月25日 03:02:40 +0000 (12:02 +0900)

committer Amit Langote <amitlan@postgresql.org>

2024年3月25日 09:06:46 +0000 (18:06 +0900)

Specifically, this commit reduces the memory consumed by the
SpecialJoinInfos that are allocated for child joins in
try_partitionwise_join() by freeing them at the end of creating paths
for each child join.

A SpecialJoinInfo allocated for a given child join is a copy of the
parent join's SpecialJoinInfo, which contains the translated copies
of the various Relids bitmapsets and semi_rhs_exprs, which is a List
of Nodes. The newly added freeing step frees the struct itself and
the various bitmapsets, but not semi_rhs_exprs, because there's no
handy function to free the memory of Node trees.

Author: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Reviewed-by: Richard Guo <guofenglinux@gmail.com>
Reviewed-by: Amit Langote <amitlangote09@gmail.com>
Reviewed-by: Andrey Lepikhov <a.lepikhov@postgrespro.ru>
Reviewed-by: Tomas Vondra <tomas.vondra@enterprisedb.com>
Discussion: https://postgr.es/m/CAExHW5tHqEf3ASVqvFFcghYGPfpy7o3xnvhHwBGbJFMRH8KjNw@mail.gmail.com

src/backend/optimizer/path/joinrels.c patch | blob | blame | history

src/backend/optimizer/util/pathnode.c patch | blob | blame | history

src/include/nodes/pathnodes.h patch | blob | blame | history

diff --git a/src/backend/optimizer/path/joinrels.c b/src/backend/optimizer/path/joinrels.c

index 4750579b0a74a230c47ea9524742bcec00a6f507..c59aff28226aa860b4c0287b7d17847b7eeccd1e 100644 (file)

--- a/src/backend/optimizer/path/joinrels.c

+++ b/src/backend/optimizer/path/joinrels.c

@@ -45,6 +45,7 @@ static void try_partitionwise_join(PlannerInfo *root, RelOptInfo *rel1,

static SpecialJoinInfo *build_child_join_sjinfo(PlannerInfo *root,

SpecialJoinInfo *parent_sjinfo,

Relids left_relids, Relids right_relids);

+static void free_child_join_sjinfo(SpecialJoinInfo *child_sjinfo);

static void compute_partition_bounds(PlannerInfo *root, RelOptInfo *rel1,

RelOptInfo *rel2, RelOptInfo *joinrel,

SpecialJoinInfo *parent_sjinfo,

@@ -1659,6 +1660,7 @@ try_partitionwise_join(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2,

child_restrictlist);

pfree(appinfos);

+ free_child_join_sjinfo(child_sjinfo);

}

@@ -1666,6 +1668,9 @@ try_partitionwise_join(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2,

* Construct the SpecialJoinInfo for a child-join by translating

* SpecialJoinInfo for the join between parents. left_relids and right_relids

* are the relids of left and right side of the join respectively.

+ *

+ * If translations are added to or removed from this function, consider

+ * updating free_child_join_sjinfo() accordingly.

static SpecialJoinInfo *

build_child_join_sjinfo(PlannerInfo *root, SpecialJoinInfo *parent_sjinfo,

@@ -1705,6 +1710,37 @@ build_child_join_sjinfo(PlannerInfo *root, SpecialJoinInfo *parent_sjinfo,

return sjinfo;

}

+/*

+ * free_child_join_sjinfo

+ * Free memory consumed by a SpecialJoinInfo created by

+ * build_child_join_sjinfo()

+ *

+ * Only members that are translated copies of their counterpart in the parent

+ * SpecialJoinInfo are freed here.

+ */

+static void

+free_child_join_sjinfo(SpecialJoinInfo *sjinfo)

+ /*

+ * Dummy SpecialJoinInfos of inner joins do not have any translated fields

+ * and hence no fields that to be freed.

+ */

+ if (sjinfo->jointype != JOIN_INNER)

+ {

+ bms_free(sjinfo->min_lefthand);

+ bms_free(sjinfo->min_righthand);

+ bms_free(sjinfo->syn_lefthand);

+ bms_free(sjinfo->syn_righthand);

+ /*

+ * semi_rhs_exprs may in principle be freed, but a simple pfree() does

+ * not suffice, so we leave it alone.

+ */

+ }

+ pfree(sjinfo);

* compute_partition_bounds

* Compute the partition bounds for a join rel from those for inputs

diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c

index 0a7e5c2678f5fb6fc6fe6785d7bc9471bdee44f6..c29ca5a0da2f9187d918bb46232e1f93986ddbe1 100644 (file)

--- a/src/backend/optimizer/util/pathnode.c

+++ b/src/backend/optimizer/util/pathnode.c

@@ -1707,8 +1707,9 @@ create_unique_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,

pathnode->subpath = subpath;

- * Under GEQO, the sjinfo might be short-lived, so we'd better make copies

- * of data structures we extract from it.

+ * Under GEQO and when planning child joins, the sjinfo might be

+ * short-lived, so we'd better make copies of data structures we extract

+ * from it.

pathnode->in_operators = copyObject(sjinfo->semi_operators);

pathnode->uniq_exprs = copyObject(sjinfo->semi_rhs_exprs);

diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h

index b3069516b2449623ee32f6cf73fd2394c84479c3..08dbee002fe26c512045f19ab72431ba6c85ff81 100644 (file)

--- a/src/include/nodes/pathnodes.h

+++ b/src/include/nodes/pathnodes.h

@@ -2856,6 +2856,9 @@ typedef struct PlaceHolderVar

* cost estimation purposes it is sometimes useful to know the join size under

* plain innerjoin semantics. Note that lhs_strict and the semi_xxx fields

* are not set meaningfully within such structs.

+ *

+ * We also create transient SpecialJoinInfos for child joins during

+ * partiotionwise join planning, which are also not present in join_info_list.

#ifndef HAVE_SPECIALJOININFO_TYPEDEF

typedef struct SpecialJoinInfo SpecialJoinInfo;

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