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Commitd297c91

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Avoid leaking memory while evaluating arguments for a table function.
ExecMakeTableFunctionResult evaluated the arguments for a function-in-FROMin the query-lifespan memory context. This is insignificant in simplecases where the function relation is scanned only once; but if the functionis in a sub-SELECT or is on the inside of a nested loop, any memoryconsumed during argument evaluation can add up quickly. (The potential fortrouble here had been foreseen long ago, per existing comments; but we'dnot previously seen a complaint from the field about it.) To fix, createan additional temporary context just for this purpose.Per an example from MauMau. Back-patch to all active branches.
1 parent2f69338 commitd297c91

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4 files changed

+29
-4
lines changed

4 files changed

+29
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lines changed

‎src/backend/executor/execQual.c

Lines changed: 11 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -1935,6 +1935,7 @@ ExecMakeFunctionResultNoSets(FuncExprState *fcache,
19351935
Tuplestorestate*
19361936
ExecMakeTableFunctionResult(ExprState*funcexpr,
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ExprContext*econtext,
1938+
MemoryContextargContext,
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TupleDescexpectedDesc,
19391940
boolrandomAccess)
19401941
{
@@ -2013,13 +2014,19 @@ ExecMakeTableFunctionResult(ExprState *funcexpr,
20132014
/*
20142015
* Evaluate the function's argument list.
20152016
*
2016-
* Note: ideally, we'd do this in the per-tuple context, but then the
2017-
* argument values would disappear when we reset the context in the
2018-
* inner loop. So do it in caller context. Perhaps we should make a
2019-
* separate context just to hold the evaluated arguments?
2017+
* We can't do this in the per-tuple context: the argument values
2018+
* would disappear when we reset that context in the inner loop. And
2019+
* the caller's CurrentMemoryContext is typically a query-lifespan
2020+
* context, so we don't want to leak memory there. We require the
2021+
* caller to pass a separate memory context that can be used for this,
2022+
* and can be reset each time through to avoid bloat.
20202023
*/
2024+
MemoryContextReset(argContext);
2025+
oldcontext=MemoryContextSwitchTo(argContext);
20212026
fcinfo.flinfo=&(fcache->func);
20222027
argDone=ExecEvalFuncArgs(&fcinfo,fcache->args,econtext);
2028+
MemoryContextSwitchTo(oldcontext);
2029+
20232030
/* We don't allow sets in the arguments of the table function */
20242031
if (argDone!=ExprSingleResult)
20252032
ereport(ERROR,

‎src/backend/executor/nodeFunctionscan.c

Lines changed: 15 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -25,6 +25,7 @@
2525
#include"executor/nodeFunctionscan.h"
2626
#include"funcapi.h"
2727
#include"utils/builtins.h"
28+
#include"utils/memutils.h"
2829

2930

3031
staticTupleTableSlot*FunctionNext(FunctionScanState*node);
@@ -64,6 +65,7 @@ FunctionNext(FunctionScanState *node)
6465
node->tuplestorestate=tuplestorestate=
6566
ExecMakeTableFunctionResult(node->funcexpr,
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node->ss.ps.ps_ExprContext,
68+
node->argcontext,
6769
node->tupdesc,
6870
node->eflags&EXEC_FLAG_BACKWARD);
6971
}
@@ -217,6 +219,19 @@ ExecInitFunctionScan(FunctionScan *node, EState *estate, int eflags)
217219
ExecAssignResultTypeFromTL(&scanstate->ss.ps);
218220
ExecAssignScanProjectionInfo(&scanstate->ss);
219221

222+
/*
223+
* Create a memory context that ExecMakeTableFunctionResult can use to
224+
* evaluate function arguments in. We can't use the per-tuple context for
225+
* this because it gets reset too often; but we don't want to leak
226+
* evaluation results into the query-lifespan context either. We just
227+
* need one context, because we evaluate each function separately.
228+
*/
229+
scanstate->argcontext=AllocSetContextCreate(CurrentMemoryContext,
230+
"Table function arguments",
231+
ALLOCSET_DEFAULT_MINSIZE,
232+
ALLOCSET_DEFAULT_INITSIZE,
233+
ALLOCSET_DEFAULT_MAXSIZE);
234+
220235
returnscanstate;
221236
}
222237

‎src/include/executor/executor.h

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -188,6 +188,7 @@ extern Datum GetAttributeByName(HeapTupleHeader tuple, const char *attname,
188188
bool*isNull);
189189
externTuplestorestate*ExecMakeTableFunctionResult(ExprState*funcexpr,
190190
ExprContext*econtext,
191+
MemoryContextargContext,
191192
TupleDescexpectedDesc,
192193
boolrandomAccess);
193194
externDatumExecEvalExprSwitchContext(ExprState*expression,ExprContext*econtext,

‎src/include/nodes/execnodes.h

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1240,6 +1240,7 @@ typedef struct SubqueryScanState
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*tupdescexpected return tuple description
12411241
*tuplestorestateprivate state of tuplestore.c
12421242
*funcexprstate for function expression being evaluated
1243+
*argcontextmemory context to evaluate function arguments in
12431244
* ----------------
12441245
*/
12451246
typedefstructFunctionScanState
@@ -1249,6 +1250,7 @@ typedef struct FunctionScanState
12491250
TupleDesctupdesc;
12501251
Tuplestorestate*tuplestorestate;
12511252
ExprState*funcexpr;
1253+
MemoryContextargcontext;
12521254
}FunctionScanState;
12531255

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/* ----------------

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