diff -rcN postgresql-8.3.12/src/backend/tcop/postgres.c postgresql-8.3.12_dev/src/backend/tcop/postgres.c
*** postgresql-8.3.12/src/backend/tcop/postgres.c	2010-10-01 22:36:12.000000000 +0900
--- postgresql-8.3.12_dev/src/backend/tcop/postgres.c	2010-12-16 15:46:43.000000000 +0900
***************
*** 914,919 ****
--- 914,921 ----
  		/*
  		 * Set up a snapshot if parse analysis/planning will need one.
  		 */
+ 		oldcontext = MemoryContextSwitchTo(MessageContext);
+ 
  		if (analyze_requires_snapshot(parsetree))
  		{
  			mySnapshot = CopySnapshot(GetTransactionSnapshot());
***************
*** 926,932 ****
  		 * Switch to appropriate context for constructing querytrees (again,
  		 * these must outlive the execution context).
  		 */
- 		oldcontext = MemoryContextSwitchTo(MessageContext);
  
  		querytree_list = pg_analyze_and_rewrite(parsetree, query_string,
  												NULL, 0);
--- 928,933 ----