8000 Fix memory leak in ARRAY(SELECT ...) subqueries. · sureandrew/postgres@b02cd9c · GitHub
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Fix memory leak in ARRAY(SELECT ...) subqueries.
Repeated execution of an uncorrelated ARRAY_SUBLINK sub-select (which I think can only happen if the sub-select is embedded in a larger, correlated subquery) would leak memory for the duration of the query, due to not reclaiming the array generated in the previous execution. Per bug #6698 from Armando Miraglia. Diagnosis and fix idea by Heikki, patch itself by me. This has been like this all along, so back-patch to all supported versions.
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2 files changed

+14
-5
lines changed

2 files changed

+14
-5
lines changed

‎src/backend/executor/nodeSubplan.c

Lines changed: 13 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -657,6 +657,7 @@ ExecInitSubPlan(SubPlan *subplan, PlanState *parent)
657657
* initialize my state
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*/
659659
sstate->curTuple = NULL;
660+
sstate->curArray = PointerGetDatum(NULL);
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sstate->projLeft = NULL;
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sstate->projRight = NULL;
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sstate->hashtable = NULL;
@@ -991,16 +992,23 @@ ExecSetParamPlan(SubPlanState *node, ExprContext *econtext)
991992
int paramid = linitial_int(subplan->setParam);
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ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
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994-
prm->execPlan = NULL;
995-
/* We build the result in query context so it won't disappear */
995+
/*
996+
* We build the result array in query context so it won't disappear;
997+
* to avoid leaking memory across repeated calls, we have to remember
998+
* the latest value, much as for curTuple above.
999+
*/
1000+
if (node->curArray != PointerGetDatum(NULL))
1001+
pfree(DatumGetPointer(node->curArray));
9961002
if (astate != NULL)
997-
prm->value = makeArrayResult(astate,
998-
econtext->ecxt_per_query_memory);
1003+
node->curArray = makeArrayResult(astate,
1004+
econtext->ecxt_per_query_memory);
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else
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{
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MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
1002-
prm->value = PointerGetDatum(construct_empty_array(subplan->firstColType));
1008+
node->curArray = PointerGetDatum(construct_empty_array(subplan->firstColType));
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}
1010+
prm->execPlan = NULL;
1011+
prm->value = node->curArray;
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prm->isnull = false;
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}
10061014
else if (!found)

‎src/include/nodes/execnodes.h

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -611,6 +611,7 @@ typedef struct SubPlanState
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ExprState *testexpr; /* state of combining expression */
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List *args; /* states of argument expression(s) */
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HeapTuple curTuple; /* copy of most recent tuple from subplan */
614+
Datum curArray; /* most recent array from ARRAY() subplan */
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/* these are used when hashing the subselect's output: */
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ProjectionInfo *projLeft; /* for projecting lefthand exprs */
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ProjectionInfo *projRight; /* for projecting subselect output */

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