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Fix ExecOpenScanRelation to take a lock on a ROW_MARK_COPY relation.

ExecOpenScanRelation assumed that any relation listed in the ExecRowMarklist has been locked by InitPlan; but this is not true if the rel'smarkType is ROW_MARK_COPY, which is possible if it's a foreign table.In most (possibly all) cases, failure to acquire a lock here isn't reallyproblematic because the parser, planner, or plancache would have taken theappropriate lock already. In principle though it might leave us vulnerableto working with a relation that we hold no lock on, and in any case if theexecutor isn't depending on previously-taken locks otherwise then it shouldnot do so for ROW_MARK_COPY relations.Noted by Etsuro Fujita. Back-patch to all active versions, since theinconsistency has been there a long time. (It's almost certainlyirrelevant in 9.0, since that predates foreign tables, but the code'sstill wrong on its own terms.)

1 parent8582ae7 commit3fbfd5dCopy full SHA for 3fbfd5d

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src/backend/executor
- execMain.c
- execUtils.c

2 files changed

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`‎src/backend/executor/execMain.c`

Lines changed: 4 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -804,6 +804,10 @@ InitPlan(QueryDesc *queryDesc, int eflags)`
`804`	`804`	`if (rc->isParent)`
`805`	`805`	`continue;`
`806`	`806`
	`807`	`+/*`
	`808`	`+ * If you change the conditions under which rel locks are acquired`
	`809`	`+ * here, be sure to adjust ExecOpenScanRelation to match.`
	`810`	`+ */`
`807`	`811`	`switch (rc->markType)`
`808`	`812`	`{`
`809`	`813`	`caseROW_MARK_EXCLUSIVE:`

`‎src/backend/executor/execUtils.c`

Lines changed: 3 additions & 1 deletion

Original file line number	Diff line number	Diff line change
`@@ -819,7 +819,9 @@ ExecOpenScanRelation(EState *estate, Index scanrelid)`
`819`	`819`	`{`
`820`	`820`	`ExecRowMark*erm=lfirst(l);`
`821`	`821`
`822`		`-if (erm->rti==scanrelid)`
	`822`	`+/* Keep this check in sync with InitPlan! */`
	`823`	`+if (erm->rti==scanrelid&&`
	`824`	`+erm->relation!=NULL)`
`823`	`825`	`{`
`824`	`826`	`lockmode=NoLock;`
`825`	`827`	`break;`

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Commit3fbfd5d

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2 files changed

2 files changed

`‎src/backend/executor/execMain.c`

`‎src/backend/executor/execUtils.c`

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