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Commitffe12d1

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author
Richard Guo
committed
Remove the RTE_GROUP RTE if we drop the groupClause
For an EXISTS subquery, the only thing that matters is whether itreturns zero or more than zero rows. Therefore, we remove certain SQLfeatures that won't affect that, among them the GROUP BY clauses.After we drop the groupClause, we'd better remove the RTE_GROUP RTEand clear the hasGroupRTE flag, as they depend on the groupClause.Failing to do so could result in a bogus RTE_GROUP entry in the parentquery, leading to an assertion failure on the hasGroupRTE flag.Reported-by: David RowleyAuthor: Richard GuoDiscussion:https://postgr.es/m/CAApHDvp2_yht8uPLyWO-kVGWZhYvx5zjGfSrg4fBQ9fsC13V0g@mail.gmail.com
1 parentd32d146 commitffe12d1

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3 files changed

+47
-0
lines changed

3 files changed

+47
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lines changed

‎src/backend/optimizer/plan/subselect.c

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@@ -1539,6 +1539,8 @@ convert_EXISTS_sublink_to_join(PlannerInfo *root, SubLink *sublink,
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staticbool
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simplify_EXISTS_query(PlannerInfo*root,Query*query)
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{
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ListCell*lc;
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/*
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* We don't try to simplify at all if the query uses set operations,
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* aggregates, grouping sets, SRFs, modifying CTEs, HAVING, OFFSET, or FOR
@@ -1607,6 +1609,28 @@ simplify_EXISTS_query(PlannerInfo *root, Query *query)
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query->sortClause=NIL;
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query->hasDistinctOn= false;
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/*
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* Since we have thrown away the GROUP BY clauses, we'd better remove the
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* RTE_GROUP RTE and clear the hasGroupRTE flag.
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*/
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foreach(lc,query->rtable)
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{
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RangeTblEntry*rte=lfirst_node(RangeTblEntry,lc);
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/*
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* Remove the RTE_GROUP RTE and clear the hasGroupRTE flag. (Since
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* we'll exit the foreach loop immediately, we don't bother with
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* foreach_delete_current.)
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*/
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if (rte->rtekind==RTE_GROUP)
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{
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Assert(query->hasGroupRTE);
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query->rtable=list_delete_cell(query->rtable,lc);
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query->hasGroupRTE= false;
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break;
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}
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}
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return true;
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}
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‎src/test/regress/expected/join.out

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@@ -3182,6 +3182,21 @@ where b.unique2 is null;
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-> Index Only Scan using tenk1_unique2 on tenk1 b
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(5 rows)
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--
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-- regression test for bogus RTE_GROUP entries
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--
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explain (costs off)
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select a.* from tenk1 a
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where exists (select 1 from tenk1 b where a.unique1 = b.unique2 group by b.unique1);
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QUERY PLAN
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------------------------------------------------------------
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Hash Semi Join
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Hash Cond: (a.unique1 = b.unique2)
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-> Seq Scan on tenk1 a
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-> Hash
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-> Index Only Scan using tenk1_unique2 on tenk1 b
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(5 rows)
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--
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-- regression test for proper handling of outer joins within antijoins
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--

‎src/test/regress/sql/join.sql

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Original file line numberDiff line numberDiff line change
@@ -818,6 +818,14 @@ explain (costs off)
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select a.*from tenk1 aleft join tenk1 bona.unique1=b.unique2
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whereb.unique2 isnull;
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--
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-- regression test for bogus RTE_GROUP entries
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--
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explain (costs off)
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select a.*from tenk1 a
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where exists (select1from tenk1 bwherea.unique1=b.unique2group byb.unique1);
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--
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-- regression test for proper handling of outer joins within antijoins
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--

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