8000 Reduce memory used by partitionwise joins · postgres/postgres@5278d0a · GitHub
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Reduce memory used by partitionwise joins
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
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+42
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lines changed

3 files changed

+42
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‎src/backend/optimizer/path/joinrels.c

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Original file line numberDiff line numberDiff line change
@@ -45,6 +45,7 @@ static void try_partitionwise_join(PlannerInfo *root, RelOptInfo *rel1,
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static SpecialJoinInfo *build_child_join_sjinfo(PlannerInfo *root,
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SpecialJoinInfo *parent_sjinfo,
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Relids left_relids, Relids right_relids);
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static void free_child_join_sjinfo(SpecialJoinInfo *child_sjinfo);
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static void compute_partition_bounds(PlannerInfo *root, RelOptInfo *rel1,
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RelOptInfo *rel2, RelOptInfo *joinrel,
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SpecialJoinInfo *parent_sjinfo,
@@ -1659,13 +1660,17 @@ try_partitionwise_join(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2,
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child_restrictlist);
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pfree(appinfos);
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free_child_join_sjinfo(child_sjinfo);
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}
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}
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/*
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* Construct the SpecialJoinInfo for a child-join by translating
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* SpecialJoinInfo for the join between parents. left_relids and right_relids
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* are the relids of left and right side of the join respectively.
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*
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* If translations are added to or removed from this function, consider
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* updating free_child_join_sjinfo() accordingly.
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*/
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static SpecialJoinInfo *
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build_child_join_sjinfo(PlannerInfo *root, SpecialJoinInfo *parent_sjinfo,
@@ -1705,6 +1710,37 @@ build_child_join_sjinfo(PlannerInfo *root, SpecialJoinInfo *parent_sjinfo,
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return sjinfo;
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}
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/*
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* free_child_join_sjinfo
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* Free memory consumed by a SpecialJoinInfo created by
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* build_child_join_sjinfo()
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*
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* Only members that are translated copies of their counterpart in the parent
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* SpecialJoinInfo are freed here.
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*/
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static void
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free_child_join_sjinfo(SpecialJoinInfo *sjinfo)
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{
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/*
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* Dummy SpecialJoinInfos of inner joins do not have any translated fields
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* and hence no fields that to be freed.
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*/
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if (sjinfo->jointype != JOIN_INNER)
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{
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bms_free(sjinfo->min_lefthand);
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bms_free(sjinfo->min_righthand);
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bms_free(sjinfo->syn_lefthand);
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bms_free(sjinfo->syn_righthand);
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/*
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* semi_rhs_exprs may in principle be freed, but a simple pfree() does
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* not suffice, so we leave it alone.
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*/
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}
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pfree(sjinfo);
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}
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/*
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* compute_partition_bounds
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* Compute the partition bounds for a join rel from those for inputs

‎src/backend/optimizer/util/pathnode.c

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1707,8 +1707,9 @@ create_unique_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,
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pathnode->subpath = subpath;
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/*
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* Under GEQO, the sjinfo might be short-lived, so we'd better make copies
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* of data structures we extract from it.
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* Under GEQO and when planning child joins, the sjinfo might be
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* short-lived, so we'd better make copies of data structures we extract
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* from it.
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*/
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pathnode->in_operators = copyObject(sjinfo->semi_operators);
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pathnode->uniq_exprs = copyObject(sjinfo->semi_rhs_exprs);

‎src/include/nodes/pathnodes.h

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2856,6 +2856,9 @@ typedef struct PlaceHolderVar
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* cost estimation purposes it is sometimes useful to know the join size under
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* plain innerjoin semantics. Note that lhs_strict and the semi_xxx fields
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* are not set meaningfully within such structs.
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*
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* We also create transient SpecialJoinInfos for child joins during
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* partiotionwise join planning, which are also not present in join_info_list.
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*/
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#ifndef HAVE_SPECIALJOININFO_TYPEDEF
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typedef struct SpecialJoinInfo SpecialJoinInfo;

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