From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sun, 10 Apr 2005 18:04:20 +0000 (+0000)
Subject: SQL functions returning pass-by-reference types were copying the results
X-Git-Tag: REL9_0_0~10439
X-Git-Url: http://git.osdn.net/view?a=commitdiff_plain;h=313de22c853bb00564c876ab1c1a3b64cb7eb0ee;p=pg-rex%2Fsyncrep.git

SQL functions returning pass-by-reference types were copying the results
into the wrong memory context, resulting in a query-lifespan memory leak.
Bug is new in 8.0, I believe.  Per report from Rae Stiening.
---

diff --git a/src/backend/executor/functions.c b/src/backend/executor/functions.c
index 521d656ff1..893ef64f03 100644
--- a/src/backend/executor/functions.c
+++ b/src/backend/executor/functions.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/functions.c,v 1.96 2005/04/06 16:34:04 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/functions.c,v 1.97 2005/04/10 18:04:20 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -86,12 +86,13 @@ static execution_state *init_execution_state(List *queryTree_list,
 static void init_sql_fcache(FmgrInfo *finfo);
 static void postquel_start(execution_state *es, SQLFunctionCachePtr fcache);
 static TupleTableSlot *postquel_getnext(execution_state *es);
-static void postquel_end(execution_state *es, SQLFunctionCachePtr fcache);
+static void postquel_end(execution_state *es);
 static void postquel_sub_params(SQLFunctionCachePtr fcache,
 					FunctionCallInfo fcinfo);
 static Datum postquel_execute(execution_state *es,
 				 FunctionCallInfo fcinfo,
-				 SQLFunctionCachePtr fcache);
+				 SQLFunctionCachePtr fcache,
+				 MemoryContext resultcontext);
 static void sql_exec_error_callback(void *arg);
 static void ShutdownSQLFunction(Datum arg);
 
@@ -384,7 +385,7 @@ postquel_getnext(execution_state *es)
 }
 
 static void
-postquel_end(execution_state *es, SQLFunctionCachePtr fcache)
+postquel_end(execution_state *es)
 {
 	Snapshot	saveActiveSnapshot;
 
@@ -454,10 +455,12 @@ postquel_sub_params(SQLFunctionCachePtr fcache,
 static Datum
 postquel_execute(execution_state *es,
 				 FunctionCallInfo fcinfo,
-				 SQLFunctionCachePtr fcache)
+				 SQLFunctionCachePtr fcache,
+				 MemoryContext resultcontext)
 {
 	TupleTableSlot *slot;
 	Datum		value;
+	MemoryContext oldcontext;
 
 	if (es->status == F_EXEC_START)
 		postquel_start(es, fcache);
@@ -470,7 +473,7 @@ postquel_execute(execution_state *es,
 		 * We fall out here for all cases except where we have obtained
 		 * a row from a function's final SELECT.
 		 */
-		postquel_end(es, fcache);
+		postquel_end(es);
 		fcinfo->isnull = true;
 		return (Datum) NULL;
 	}
@@ -482,8 +485,12 @@ postquel_execute(execution_state *es,
 	Assert(LAST_POSTQUEL_COMMAND(es));
 
 	/*
-	 * Set up to return the function value.
+	 * Set up to return the function value.  For pass-by-reference
+	 * datatypes, be sure to allocate the result in resultcontext,
+	 * not the current memory context (which has query lifespan).
 	 */
+	oldcontext = MemoryContextSwitchTo(resultcontext);
+
 	if (fcache->returnsTuple)
 	{
 		/*
@@ -492,7 +499,7 @@ postquel_execute(execution_state *es,
 		 * reasons why we do this:
 		 *
 		 * 1. To copy the tuple out of the child execution context and
-		 * into our own context.
+		 * into the desired result context.
 		 *
 		 * 2. To remove any junk attributes present in the raw subselect
 		 * result.  (This is probably not absolutely necessary, but it
@@ -553,8 +560,8 @@ postquel_execute(execution_state *es,
 	{
 		/*
 		 * Returning a scalar, which we have to extract from the first
-		 * column of the SELECT result, and then copy into current
-		 * execution context if needed.
+		 * column of the SELECT result, and then copy into result
+		 * context if needed.
 		 */
 		value = slot_getattr(slot, 1, &(fcinfo->isnull));
 
@@ -562,12 +569,14 @@ postquel_execute(execution_state *es,
 			value = datumCopy(value, fcache->typbyval, fcache->typlen);
 	}
 
+	MemoryContextSwitchTo(oldcontext);
+
 	/*
 	 * If this is a single valued function we have to end the function
 	 * execution now.
 	 */
 	if (!fcinfo->flinfo->fn_retset)
-		postquel_end(es, fcache);
+		postquel_end(es);
 
 	return value;
 }
@@ -627,7 +636,7 @@ fmgr_sql(PG_FUNCTION_ARGS)
 	 */
 	while (es)
 	{
-		result = postquel_execute(es, fcinfo, fcache);
+		result = postquel_execute(es, fcinfo, fcache, oldcontext);
 		if (es->status != F_EXEC_DONE)
 			break;
 		es = es->next;
@@ -824,7 +833,7 @@ ShutdownSQLFunction(Datum arg)
 	{
 		/* Shut down anything still running */
 		if (es->status == F_EXEC_RUN)
-			postquel_end(es, fcache);
+			postquel_end(es);
 		/* Reset states to START in case we're called again */
 		es->status = F_EXEC_START;
 		es = es->next;