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Fix plancache refcount leak after error in ExecuteQuery.

When stuffing a plan from the plancache into a Portal, one isnot supposed to risk throwing an error between GetCachedPlan andPortalDefineQuery; if that happens, the plan refcount incrementedby GetCachedPlan will be leaked. I managed to break this rulewhile refactoring code in9dbf2b7. There is no visibleconsequence other than some memory leakage, and since nobody isvery likely to trigger the relevant error conditions many timesin a row, it's not surprising we haven't noticed. Nonetheless,it's a bug, so rearrange the order of operations to remove thehazard.Noted on the way to looking for a better fix for bug #17053.This mistake is pretty old, so back-patch to all supportedbranches.

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src/backend/commands
- prepare.c

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+11

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`‎src/backend/commands/prepare.c`

Lines changed: 11 additions & 7 deletions

Original file line number	Diff line number	Diff line change
`@@ -233,6 +233,17 @@ ExecuteQuery(ParseState *pstate,`
`233`	`233`	`cplan=GetCachedPlan(entry->plansource,paramLI,NULL,NULL);`
`234`	`234`	`plan_list=cplan->stmt_list;`
`235`	`235`
	`236`	`+/*`
	`237`	`+ * DO NOT add any logic that could possibly throw an error between`
	`238`	`+ * GetCachedPlan and PortalDefineQuery, or you'll leak the plan refcount.`
	`239`	`+ */`
	`240`	`+PortalDefineQuery(portal,`
	`241`	`+NULL,`
	`242`	`+query_string,`
	`243`	`+entry->plansource->commandTag,`
	`244`	`+plan_list,`
	`245`	`+cplan);`
	`246`	`+`
`236`	`247`	`/*`
`237`	`248`	`* For CREATE TABLE ... AS EXECUTE, we must verify that the prepared`
`238`	`249`	`* statement is one that produces tuples. Currently we insist that it be`
`@@ -276,13 +287,6 @@ ExecuteQuery(ParseState *pstate,`
`276`	`287`	`count=FETCH_ALL;`
`277`	`288`	`}`
`278`	`289`
`279`		`-PortalDefineQuery(portal,`
`280`		`-NULL,`
`281`		`-query_string,`
`282`		`-entry->plansource->commandTag,`
`283`		`-plan_list,`
`284`		`-cplan);`
`285`		`-`
`286`	`290`	`/*`
`287`	`291`	`* Run the portal as appropriate.`
`288`	`292`	`*/`

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Commit131ea3e

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`‎src/backend/commands/prepare.c`

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