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Commit299298b

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Fix transient memory leak for SRFs in FROM.
Ina9c35cf I changed ExecMakeTableFunctionResult() to dynamicallyallocate the FunctionCallInfo used to call the SRF. Unfortunately Idid not account for the fact that the surrounding memory context hasquery lifetime, leading to a leak till the end of the query.In most cases the leak is fairly inconsequential, but if theFunctionScan is done many times in the query, the leak can addup. This happens e.g. if the function scan is on the inner side of anested loop, due to a lateral join.EXPLAIN SELECT sum(f) FROM generate_series(1, 100000000) g(i), generate_series(i, i+1) f;quickly shows the leak.Instead of explicitly freeing the FunctionCallInfo it seems better tomake sure all the per-set temporary state inExecMakeTableFunctionResult() is cleaned up wholesale. Currentlythat's probably just the FunctionCallInfo allocation, but sincethere's some initialization work, and since there's already anappropriate context, this seems like a more robust approach.Bug: #16112Reported-By: Ben CornettAuthor: Andres FreundReviewed-By: Tom LaneDiscussion:https://postgr.es/m/16112-4448bbf55a404189%40postgresql.orgBackpatch: 12,a9c35cf
1 parent0a89e93 commit299298b

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1 file changed

+29
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‎src/backend/executor/execSRF.c

Lines changed: 29 additions & 21 deletions
Original file line numberDiff line numberDiff line change
@@ -114,10 +114,23 @@ ExecMakeTableFunctionResult(SetExprState *setexpr,
114114
ReturnSetInforsinfo;
115115
HeapTupleDatatmptup;
116116
MemoryContextcallerContext;
117-
MemoryContextoldcontext;
118117
boolfirst_time= true;
119118

120-
callerContext=CurrentMemoryContext;
119+
/*
120+
* Execute per-tablefunc actions in appropriate context.
121+
*
122+
* The FunctionCallInfo needs to live across all the calls to a
123+
* ValuePerCall function, so it can't be allocated in the per-tuple
124+
* context. Similarly, the function arguments need to be evaluated in a
125+
* context that is longer lived than the per-tuple context: The argument
126+
* values would otherwise disappear when we reset that context in the
127+
* inner loop. As the caller's CurrentMemoryContext is typically a
128+
* query-lifespan context, we don't want to leak memory there. We require
129+
* the caller to pass a separate memory context that can be used for this,
130+
* and can be reset each time through to avoid bloat.
131+
*/
132+
MemoryContextReset(argContext);
133+
callerContext=MemoryContextSwitchTo(argContext);
121134

122135
funcrettype=exprType((Node*)setexpr->expr);
123136

@@ -163,21 +176,9 @@ ExecMakeTableFunctionResult(SetExprState *setexpr,
163176
list_length(setexpr->args),
164177
setexpr->fcinfo->fncollation,
165178
NULL, (Node*)&rsinfo);
166-
167-
/*
168-
* Evaluate the function's argument list.
169-
*
170-
* We can't do this in the per-tuple context: the argument values
171-
* would disappear when we reset that context in the inner loop. And
172-
* the caller's CurrentMemoryContext is typically a query-lifespan
173-
* context, so we don't want to leak memory there. We require the
174-
* caller to pass a separate memory context that can be used for this,
175-
* and can be reset each time through to avoid bloat.
176-
*/
177-
MemoryContextReset(argContext);
178-
oldcontext=MemoryContextSwitchTo(argContext);
179+
/* evaluate the function's argument list */
180+
Assert(CurrentMemoryContext==argContext);
179181
ExecEvalFuncArgs(fcinfo,setexpr->args,econtext);
180-
MemoryContextSwitchTo(oldcontext);
181182

182183
/*
183184
* If function is strict, and there are any NULL arguments, skip
@@ -217,7 +218,7 @@ ExecMakeTableFunctionResult(SetExprState *setexpr,
217218
CHECK_FOR_INTERRUPTS();
218219

219220
/*
220-
*reset per-tuple memory context before each call of the function or
221+
*Reset per-tuple memory context before each call of the function or
221222
* expression. This cleans up any local memory the function may leak
222223
* when called.
223224
*/
@@ -257,7 +258,9 @@ ExecMakeTableFunctionResult(SetExprState *setexpr,
257258
*/
258259
if (first_time)
259260
{
260-
oldcontext=MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
261+
MemoryContextoldcontext=
262+
MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
263+
261264
tupstore=tuplestore_begin_heap(randomAccess, false,work_mem);
262265
rsinfo.setResult=tupstore;
263266
if (!returnsTuple)
@@ -285,13 +288,15 @@ ExecMakeTableFunctionResult(SetExprState *setexpr,
285288

286289
if (tupdesc==NULL)
287290
{
291+
MemoryContextoldcontext=
292+
MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
293+
288294
/*
289295
* This is the first non-NULL result from the
290296
* function. Use the type info embedded in the
291297
* rowtype Datum to look up the needed tupdesc. Make
292298
* a copy for the query.
293299
*/
294-
oldcontext=MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
295300
tupdesc=lookup_rowtype_tupdesc_copy(HeapTupleHeaderGetTypeId(td),
296301
HeapTupleHeaderGetTypMod(td));
297302
rsinfo.setDesc=tupdesc;
@@ -378,15 +383,18 @@ ExecMakeTableFunctionResult(SetExprState *setexpr,
378383
*/
379384
if (rsinfo.setResult==NULL)
380385
{
381-
MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
386+
MemoryContextoldcontext=
387+
MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
388+
382389
tupstore=tuplestore_begin_heap(randomAccess, false,work_mem);
383390
rsinfo.setResult=tupstore;
391+
MemoryContextSwitchTo(oldcontext);
392+
384393
if (!returnsSet)
385394
{
386395
intnatts=expectedDesc->natts;
387396
bool*nullflags;
388397

389-
MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);
390398
nullflags= (bool*)palloc(natts*sizeof(bool));
391399
memset(nullflags, true,natts*sizeof(bool));
392400
tuplestore_putvalues(tupstore,expectedDesc,NULL,nullflags);

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