SPI_exec shouldn't return SPI_OK_SELECT if it hasn't actually returned

a tuple table.  Fixes core dump in pltcl (and probably other PLs) when
executing a query rewritten by a rule.  Per bug report from Wolfgang Walter.

Author: tglsfdc

src/backend/executor/spi.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/spi.c,v 1.84 2003/01/21 22:06:12 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/spi.c,v 1.85 2003/01/29 15:24:46 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -124,6 +124,14 @@ SPI_finish(void)
 	MemoryContextDelete(_SPI_current->execCxt);
 	MemoryContextDelete(_SPI_current->procCxt);
 
+	/*
+	 * Reset result variables, especially SPI_tuptable which is probably
+	 * pointing at a just-deleted tuptable
+	 */
+	SPI_processed = 0;
+	SPI_lastoid = InvalidOid;
+	SPI_tuptable = NULL;
+
 	/*
 	 * After _SPI_begin_call _SPI_connected == _SPI_curid. Now we are
 	 * closing connection to SPI and returning to upper Executor and so
@@ -1314,6 +1322,11 @@ _SPI_pquery(QueryDesc *queryDesc, bool runit, int tcount)
 		SPI_lastoid = save_lastoid;
 		SPI_tuptable = _SPI_current->tuptable;
 	}
+	else if (res == SPI_OK_SELECT)
+	{
+		/* Don't return SPI_OK_SELECT if we discarded the result */
+		res = SPI_OK_UTILITY;
+	}
 
 	ExecutorEnd(queryDesc);