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Fix EvalPlanQual rechecking during MERGE.

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Under some circumstances, concurrent MERGE operations could lead to
inconsistent results, that varied according the plan chosen. This was
caused by a lack of rowmarks on the source relation, which meant that
EvalPlanQual rechecking was not guaranteed to return the same source
tuples when re-running the join query.

Fix by ensuring that preprocess_rowmarks() sets up PlanRowMarks for
all non-target relations used in MERGE, in the same way that it does
for UPDATE and DELETE.

Per bug #18103. Back-patch to v15, where MERGE was introduced.

Dean Rasheed, reviewed by Richard Guo.

Discussion: https://postgr.es/m/18103-c4386baab8e355e3%40postgresql.org
This commit is contained in:
Dean Rasheed
2023-09-30 10:52:21 +01:00
parent f02154652d
commit 1d5caec221
10 changed files with 237 additions and 38 deletions
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6
src/backend/executor/nodeModifyTable.c
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@ -4284,9 +4284,9 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
/*
* If we have any secondary relations in an UPDATE or DELETE, they need to
* be treated like non-locked relations in SELECT FOR UPDATE, ie, the
* EvalPlanQual mechanism needs to be told about them. Locate the
* relevant ExecRowMarks.
* be treated like non-locked relations in SELECT FOR UPDATE, i.e., the
* EvalPlanQual mechanism needs to be told about them. This also goes for
* the source relations in a MERGE. Locate the relevant ExecRowMarks.
*/
arowmarks = NIL;
foreach(l, node->rowMarks)