Adjust nodeFunctionscan.c to reset transient memory context between calls

to the table function, thus preventing memory leakage accumulation across
calls.  This means that SRFs need to be careful to distinguish permanent
and local storage; adjust code and documentation accordingly.  Patch by
Joe Conway, very minor tweaks by Tom Lane.

3 files changed, 36 insertions, 34 deletions

diff --git a/src/backend/utils/adt/lockfuncs.c b/src/backend/utils/adt/lockfuncs.c
index 83d0d1051df..199efbacd26 100644
--- a/src/backend/utils/adt/lockfuncs.c
+++ b/src/backend/utils/adt/lockfuncs.c
@@ -5,7 +5,7 @@
  * Copyright (c) 2002, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *		$Header: /cvsroot/pgsql/src/backend/utils/adt/lockfuncs.c,v 1.3 2002/08/29 00:17:05 tgl Exp $
+ *		$Header: /cvsroot/pgsql/src/backend/utils/adt/lockfuncs.c,v 1.4 2002/08/29 17:14:33 tgl Exp $
  */
 #include "postgres.h"
 
@@ -24,15 +24,20 @@ static int next_lock(int locks[]);
 Datum
 pg_lock_status(PG_FUNCTION_ARGS)
 {
-	FuncCallContext		*funccxt;
-	LockData			*lockData;
+	FuncCallContext	   *funcctx;
+	LockData		   *lockData;
+	MemoryContext		oldcontext;
 
 	if (SRF_IS_FIRSTCALL())
 	{
-		MemoryContext	oldcxt;
 		TupleDesc		tupdesc;
 
-		funccxt = SRF_FIRSTCALL_INIT();
+		/* create a function context for cross-call persistence */
+		funcctx = SRF_FIRSTCALL_INIT();
+
+		/* switch to memory context appropriate for multiple function calls */
+		oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
+
 		tupdesc = CreateTemplateTupleDesc(5, WITHOUTOID);
 		TupleDescInitEntry(tupdesc, (AttrNumber) 1, "relation",
 						   OIDOID, -1, 0, false);
@@ -45,10 +50,8 @@ pg_lock_status(PG_FUNCTION_ARGS)
 		TupleDescInitEntry(tupdesc, (AttrNumber) 5, "isgranted",
 						   BOOLOID, -1, 0, false);
 
-		funccxt->slot = TupleDescGetSlot(tupdesc);
-		funccxt->attinmeta = TupleDescGetAttInMetadata(tupdesc);
-
-		oldcxt = MemoryContextSwitchTo(funccxt->fmctx);
+		funcctx->slot = TupleDescGetSlot(tupdesc);
+		funcctx->attinmeta = TupleDescGetAttInMetadata(tupdesc);
 
 		/*
 		 * Preload all the locking information that we will eventually format
@@ -56,15 +59,15 @@ pg_lock_status(PG_FUNCTION_ARGS)
 		 * MemoryContext is reset when the SRF finishes, we don't need to
 		 * free it ourselves.
 		 */
-		funccxt->user_fctx = (LockData *) palloc(sizeof(LockData));
+		funcctx->user_fctx = (LockData *) palloc(sizeof(LockData));
 
-		GetLockStatusData(funccxt->user_fctx);
+		GetLockStatusData(funcctx->user_fctx);
 
-		MemoryContextSwitchTo(oldcxt);
+		MemoryContextSwitchTo(oldcontext);
 	}
 
-	funccxt	= SRF_PERCALL_SETUP();
-	lockData = (LockData *) funccxt->user_fctx;
+	funcctx	= SRF_PERCALL_SETUP();
+	lockData = (LockData *) funcctx->user_fctx;
 
 	while (lockData->currIdx < lockData->nelements)
 	{
@@ -82,7 +85,7 @@ pg_lock_status(PG_FUNCTION_ARGS)
 		holder		= &(lockData->holders[currIdx]);
 		lock		= &(lockData->locks[currIdx]);
 		proc		= &(lockData->procs[currIdx]);
-		num_attrs	= funccxt->attinmeta->tupdesc->natts;
+		num_attrs	= funcctx->attinmeta->tupdesc->natts;
 
 		values = (char **) palloc(sizeof(*values) * num_attrs);
 
@@ -133,12 +136,12 @@ pg_lock_status(PG_FUNCTION_ARGS)
 
 		strncpy(values[3], GetLockmodeName(mode), 32);
 
-		tuple = BuildTupleFromCStrings(funccxt->attinmeta, values);
-		result = TupleGetDatum(funccxt->slot, tuple);
-		SRF_RETURN_NEXT(funccxt, result);
+		tuple = BuildTupleFromCStrings(funcctx->attinmeta, values);
+		result = TupleGetDatum(funcctx->slot, tuple);
+		SRF_RETURN_NEXT(funcctx, result);
 	}
 
-	SRF_RETURN_DONE(funccxt);
+	SRF_RETURN_DONE(funcctx);
 }
 
 static LOCKMODE
diff --git a/src/backend/utils/fmgr/funcapi.c b/src/backend/utils/fmgr/funcapi.c
index 28311c26b7b..35ba972fe12 100644
--- a/src/backend/utils/fmgr/funcapi.c
+++ b/src/backend/utils/fmgr/funcapi.c
@@ -7,7 +7,7 @@
  * Copyright (c) 2002, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/utils/fmgr/funcapi.c,v 1.3 2002/08/29 00:17:05 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/fmgr/funcapi.c,v 1.4 2002/08/29 17:14:33 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -39,16 +39,12 @@ init_MultiFuncCall(PG_FUNCTION_ARGS)
 	{
 		/*
 		 * First call
+		 *
+		 * Allocate suitably long-lived space and zero it
 		 */
-		MemoryContext oldcontext;
-
-		/* switch to the appropriate memory context */
-		oldcontext = MemoryContextSwitchTo(fcinfo->flinfo->fn_mcxt);
-
-		/*
-		 * allocate space and zero it
-		 */
-		retval = (FuncCallContext *) palloc(sizeof(FuncCallContext));
+		retval = (FuncCallContext *)
+			MemoryContextAlloc(fcinfo->flinfo->fn_mcxt,
+							   sizeof(FuncCallContext));
 		MemSet(retval, 0, sizeof(FuncCallContext));
 
 		/*
@@ -59,15 +55,12 @@ init_MultiFuncCall(PG_FUNCTION_ARGS)
 		retval->slot = NULL;
 		retval->user_fctx = NULL;
 		retval->attinmeta = NULL;
-		retval->fmctx = fcinfo->flinfo->fn_mcxt;
+		retval->multi_call_memory_ctx = fcinfo->flinfo->fn_mcxt;
 
 		/*
 		 * save the pointer for cross-call use
 		 */
 		fcinfo->flinfo->fn_extra = retval;
-
-		/* back to the original memory context */
-		MemoryContextSwitchTo(oldcontext);
 	}
 	else	/* second and subsequent calls */
 	{
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 660cd124ba9..5114fcc38f2 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -5,7 +5,7 @@
  * command, configuration file, and command line options.
  * See src/backend/utils/misc/README for more information.
  *
- * $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.85 2002/08/29 00:17:05 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.86 2002/08/29 17:14:33 tgl Exp $
  *
  * Copyright 2000 by PostgreSQL Global Development Group
  * Written by Peter Eisentraut <peter_e@gmx.net>.
@@ -2421,6 +2421,7 @@ show_all_settings(PG_FUNCTION_ARGS)
 	int					max_calls;
 	TupleTableSlot	   *slot;
 	AttInMetadata	   *attinmeta;
+	MemoryContext		oldcontext;
 
 	/* stuff done only on the first call of the function */
  	if(SRF_IS_FIRSTCALL())
@@ -2428,6 +2429,9 @@ show_all_settings(PG_FUNCTION_ARGS)
 		/* create a function context for cross-call persistence */
  		funcctx = SRF_FIRSTCALL_INIT();
 
+		/* switch to memory context appropriate for multiple function calls */
+		oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
+
 		/* need a tuple descriptor representing two TEXT columns */
 		tupdesc = CreateTemplateTupleDesc(2, WITHOUTOID);
 		TupleDescInitEntry(tupdesc, (AttrNumber) 1, "name",
@@ -2450,6 +2454,8 @@ show_all_settings(PG_FUNCTION_ARGS)
 
 		/* total number of tuples to be returned */
 		funcctx->max_calls = GetNumConfigOptions();
+
+		MemoryContextSwitchTo(oldcontext);
     }
 
 	/* stuff done on every call of the function */