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Commit33a4699

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Avoid crash with WHERE CURRENT OF and a custom scan plan.
execCurrent.c's search_plan_tree() assumed that ForeignScanStatesand CustomScanStates necessarily have a valid ss_currentRelation.This is demonstrably untrue for postgres_fdw's remote join andremote aggregation plans, and non-leaf custom scans might not havean identifiable scan relation either. Avoid crashing by ignoringsuch nodes when the field is null.This solution will lead to errors like 'cursor "foo" is not asimply updatable scan of table "bar"' in cases where maybe wecould have allowed WHERE CURRENT OF to work. That's not an issuefor postgres_fdw's usages, since joins or aggregations would renderWHERE CURRENT OF invalid anyway. But an otherwise-transparentupper level custom scan node might find this annoying. When and ifsomeone cares to expend work on such a scenario, we could invent acustom-scan-provider callback to determine what's safe.Report and patch by David Geier, commentary by me. It's been likethis for awhile, so back-patch to all supported branches.Discussion:https://postgr.es/m/0253344d-9bdd-11c4-7f0d-d88c02cd7991@swarm64.com
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‎src/backend/executor/execCurrent.c

Lines changed: 8 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -314,7 +314,12 @@ search_plan_tree(PlanState *node, Oid table_oid,
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switch (nodeTag(node))
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{
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/*
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* Relation scan nodes can all be treated alike
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* Relation scan nodes can all be treated alike. Note that
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* ForeignScan and CustomScan might not have a currentRelation, in
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* which case we just ignore them. (We dare not descend to any
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* child plan nodes they might have, since we do not know the
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* relationship of such a node's current output tuple to the
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* children's current outputs.)
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*/
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caseT_SeqScanState:
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caseT_SampleScanState:
@@ -327,7 +332,8 @@ search_plan_tree(PlanState *node, Oid table_oid,
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{
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ScanState*sstate= (ScanState*)node;
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330-
if (RelationGetRelid(sstate->ss_currentRelation)==table_oid)
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if (sstate->ss_currentRelation&&
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RelationGetRelid(sstate->ss_currentRelation)==table_oid)
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result=sstate;
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break;
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}

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