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.

1 files changed, 21 insertions, 7 deletions

diff --git a/contrib/tablefunc/tablefunc.c b/contrib/tablefunc/tablefunc.c
index d05fc1a76b6..37a6e723a65 100644
--- a/contrib/tablefunc/tablefunc.c
+++ b/contrib/tablefunc/tablefunc.c
@@ -87,6 +87,7 @@ normal_rand(PG_FUNCTION_ARGS)
 	float8				stddev;
 	float8				carry_val;
 	bool				use_carry;
+	MemoryContext		oldcontext;
 
 	/* stuff done only on the first call of the function */
  	if(SRF_IS_FIRSTCALL())
@@ -94,6 +95,9 @@ normal_rand(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);
+
 		/* total number of tuples to be returned */
 		funcctx->max_calls = PG_GETARG_UINT32(0);
 
@@ -119,6 +123,8 @@ normal_rand(PG_FUNCTION_ARGS)
 		 * purpose it doesn't matter, just cast it as an unsigned value
 		 */
 		srandom(PG_GETARG_UINT32(3));
+
+		MemoryContextSwitchTo(oldcontext);
     }
 
 	/* stuff done on every call of the function */
@@ -260,10 +266,11 @@ crosstab(PG_FUNCTION_ARGS)
 	AttInMetadata	   *attinmeta;
 	SPITupleTable	   *spi_tuptable = NULL;
 	TupleDesc			spi_tupdesc;
-	char			   *lastrowid;
+	char			   *lastrowid = NULL;
 	crosstab_fctx	   *fctx;
 	int					i;
 	int					num_categories;
+	MemoryContext		oldcontext;
 
 	/* stuff done only on the first call of the function */
  	if(SRF_IS_FIRSTCALL())
@@ -275,13 +282,12 @@ crosstab(PG_FUNCTION_ARGS)
 		TupleDesc		tupdesc = NULL;
 		int				ret;
 		int				proc;
-		MemoryContext	oldcontext;
 
 		/* create a function context for cross-call persistence */
  		funcctx = SRF_FIRSTCALL_INIT();
 
-		/* SPI switches context on us, so save it first */
-		oldcontext = CurrentMemoryContext;
+		/* switch to memory context appropriate for multiple function calls */
+		oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
 
 		/* Connect to SPI manager */
 		if ((ret = SPI_connect()) < 0)
@@ -317,8 +323,8 @@ crosstab(PG_FUNCTION_ARGS)
 	 		SRF_RETURN_DONE(funcctx);
 		}
 
-		/* back to the original memory context */
-		MemoryContextSwitchTo(oldcontext);
+		/* SPI switches context on us, so reset it */
+		MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
 
 		/* get the typeid that represents our return type */
 		functypeid = get_func_rettype(funcid);
@@ -381,6 +387,8 @@ crosstab(PG_FUNCTION_ARGS)
 
 		/* total number of tuples to be returned */
 		funcctx->max_calls = proc;
+
+		MemoryContextSwitchTo(oldcontext);
     }
 
 	/* stuff done on every call of the function */
@@ -432,7 +440,7 @@ crosstab(PG_FUNCTION_ARGS)
 			for (i = 0; i < num_categories; i++)
 			{
 				HeapTuple	spi_tuple;
-				char	   *rowid;
+				char	   *rowid = NULL;
 
 				/* see if we've gone too far already */
 				if (call_cntr >= max_calls)
@@ -496,7 +504,13 @@ crosstab(PG_FUNCTION_ARGS)
 			xpfree(fctx->lastrowid);
 
 			if (values[0] != NULL)
+			{
+				/* switch to memory context appropriate for multiple function calls */
+				oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
+
 				lastrowid = fctx->lastrowid = pstrdup(values[0]);
+				MemoryContextSwitchTo(oldcontext);
+			}
 
 			if (!allnulls)
 			{