Revert my bad decision of about a year ago to make PortalDefineQuery

responsible for copying the query string into the new Portal.  Such copying
is unnecessary in the common code path through exec_simple_query, and in
this case it can be enormously expensive because the string might contain
a large number of individual commands; we were copying the entire, long
string for each command, resulting in O(N^2) behavior for N commands.
(This is the cause of bug #4079.)  A second problem with it is that
PortalDefineQuery really can't risk error, because if it elog's before
having set up the Portal, we will leak the plancache refcount that the
caller is trying to hand off to the portal.  So go back to the design in
which the caller is responsible for making sure everything is copied into
the portal if necessary.

1 files changed, 18 insertions, 4 deletions

diff --git a/src/backend/executor/spi.c b/src/backend/executor/spi.c
index 42187fe43ad..f7d41373b4a 100644
--- a/src/backend/executor/spi.c
+++ b/src/backend/executor/spi.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/spi.c,v 1.192 2008/04/01 03:09:30 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/spi.c,v 1.193 2008/04/02 18:31:50 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -918,6 +918,7 @@ SPI_cursor_open(const char *name, SPIPlanPtr plan,
 	CachedPlanSource *plansource;
 	CachedPlan *cplan;
 	List	   *stmt_list;
+	char	   *query_string;
 	ParamListInfo paramLI;
 	Snapshot	snapshot;
 	MemoryContext oldcontext;
@@ -968,10 +969,22 @@ SPI_cursor_open(const char *name, SPIPlanPtr plan,
 		portal = CreatePortal(name, false, false);
 	}
 
+	/*
+	 * Prepare to copy stuff into the portal's memory context.  We do all this
+	 * copying first, because it could possibly fail (out-of-memory) and we
+	 * don't want a failure to occur between RevalidateCachedPlan and
+	 * PortalDefineQuery; that would result in leaking our plancache refcount.
+	 */
+	oldcontext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
+
+	/* Copy the plan's query string, if available, into the portal */
+	query_string = plansource->query_string;
+	if (query_string)
+		query_string = pstrdup(query_string);
+
 	/* If the plan has parameters, copy them into the portal */
 	if (plan->nargs > 0)
 	{
-		oldcontext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
 		/* sizeof(ParamListInfoData) includes the first array element */
 		paramLI = (ParamListInfo) palloc(sizeof(ParamListInfoData) +
 								 (plan->nargs - 1) *sizeof(ParamExternData));
@@ -1000,11 +1013,12 @@ SPI_cursor_open(const char *name, SPIPlanPtr plan,
 									   paramTypByVal, paramTypLen);
 			}
 		}
-		MemoryContextSwitchTo(oldcontext);
 	}
 	else
 		paramLI = NULL;
 
+	MemoryContextSwitchTo(oldcontext);
+
 	if (plan->saved)
 	{
 		/* Replan if needed, and increment plan refcount for portal */
@@ -1025,7 +1039,7 @@ SPI_cursor_open(const char *name, SPIPlanPtr plan,
 	 */
 	PortalDefineQuery(portal,
 					  NULL,		/* no statement name */
-					  plansource->query_string,
+					  query_string,
 					  plansource->commandTag,
 					  stmt_list,
 					  cplan);