Reimplementation of UNION/INTERSECT/EXCEPT. INTERSECT/EXCEPT now meet the

SQL92 semantics, including support for ALL option.  All three can be used
in subqueries and views.  DISTINCT and ORDER BY work now in views, too.
This rewrite fixes many problems with cross-datatype UNIONs and INSERT/SELECT
where the SELECT yields different datatypes than the INSERT needs.  I did
that by making UNION subqueries and SELECT in INSERT be treated like
subselects-in-FROM, thereby allowing an extra level of targetlist where the
datatype conversions can be inserted safely.
INITDB NEEDED!

1 files changed, 14 insertions, 4 deletions

diff --git a/src/backend/executor/nodeSubplan.c b/src/backend/executor/nodeSubplan.c
index aee6911e5e4..933dcc83425 100644
--- a/src/backend/executor/nodeSubplan.c
+++ b/src/backend/executor/nodeSubplan.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/nodeSubplan.c,v 1.27 2000/08/24 03:29:03 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/nodeSubplan.c,v 1.28 2000/10/05 19:11:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -328,7 +328,14 @@ ExecInitSubPlan(SubPlan *node, EState *estate, Plan *parent)
 /* ----------------------------------------------------------------
  *		ExecSetParamPlan
  *
- *		Executes plan of node and sets parameters.
+ *		Executes an InitPlan subplan and sets its output parameters.
+ *
+ * This is called from ExecEvalParam() when the value of a PARAM_EXEC
+ * parameter is requested and the param's execPlan field is set (indicating
+ * that the param has not yet been evaluated).  This allows lazy evaluation
+ * of initplans: we don't run the subplan until/unless we need its output.
+ * Note that this routine MUST clear the execPlan fields of the plan's
+ * output parameters after evaluating them!
  * ----------------------------------------------------------------
  */
 void
@@ -424,13 +431,13 @@ ExecSetParamPlan(SubPlan *node, ExprContext *econtext)
 		}
 	}
 
-	MemoryContextSwitchTo(oldcontext);
-
 	if (plan->extParam == NULL) /* un-correlated ... */
 	{
 		ExecEndNode(plan, plan);
 		node->needShutdown = false;
 	}
+
+	MemoryContextSwitchTo(oldcontext);
 }
 
 /* ----------------------------------------------------------------
@@ -470,6 +477,9 @@ ExecReScanSetParamPlan(SubPlan *node, Plan *parent)
 	 * node->plan->chgParam is not NULL... ExecReScan (plan, NULL, plan);
 	 */
 
+	/*
+	 * Mark this subplan's output parameters as needing recalculation
+	 */
 	foreach(lst, node->setParam)
 	{
 		ParamExecData *prm = &(plan->state->es_param_exec_vals[lfirsti(lst)]);