From 38423232a5c7689bf41a9ab47086fbd6edecfd73 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Thu, 18 Dec 2003 20:21:37 +0000
Subject: [PATCH] Ensure set-returning functions in the targetlist of a plan
 node will be shut down cleanly if the plan node is ReScanned before the SRFs
 are run to completion.  This fixes the problem for SQL-language functions,
 but still need work on functions using the SRF_XXX() macros.

---
 src/backend/executor/execAmi.c   | 26 +++++++++++++++++++-------
 src/backend/executor/execUtils.c | 21 ++++++++++++++++++++-
 src/include/executor/executor.h  |  3 ++-
 3 files changed, 41 insertions(+), 9 deletions(-)

diff --git a/src/backend/executor/execAmi.c b/src/backend/executor/execAmi.c
index 60a7d59bef8..d9a24a34484 100644
--- a/src/backend/executor/execAmi.c
+++ b/src/backend/executor/execAmi.c
@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- *	$PostgreSQL: pgsql/src/backend/executor/execAmi.c,v 1.76 2003/11/29 19:51:48 pgsql Exp $
+ *	$PostgreSQL: pgsql/src/backend/executor/execAmi.c,v 1.77 2003/12/18 20:21:37 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -39,13 +39,20 @@
 #include "executor/nodeUnique.h"
 
 
-/* ----------------------------------------------------------------
- *		ExecReScan
+/*
+ * ExecReScan
+ *		Reset a plan node so that its output can be re-scanned.
  *
- *		takes the new expression context as an argument, so that
- *		index scans needn't have their scan keys updated separately
- *		- marcel 09/20/94
- * ----------------------------------------------------------------
+ * Note that if the plan node has parameters that have changed value,
+ * the output might be different from last time.
+ *
+ * The second parameter is currently only used to pass a NestLoop plan's
+ * econtext down to its inner child plan, in case that is an indexscan that
+ * needs access to variables of the current outer tuple.  (The handling of
+ * this parameter is currently pretty inconsistent: some callers pass NULL
+ * and some pass down their parent's value; so don't rely on it in other
+ * situations.  It'd probably be better to remove the whole thing and use
+ * the generalized parameter mechanism instead.)
  */
 void
 ExecReScan(PlanState *node, ExprContext *exprCtxt)
@@ -85,6 +92,11 @@ ExecReScan(PlanState *node, ExprContext *exprCtxt)
 			UpdateChangedParamSet(node->righttree, node->chgParam);
 	}
 
+	/* Shut down any SRFs in the plan node's targetlist */
+	if (node->ps_ExprContext)
+		ReScanExprContext(node->ps_ExprContext);
+
+	/* And do node-type-specific processing */
 	switch (nodeTag(node))
 	{
 		case T_ResultState:
diff --git a/src/backend/executor/execUtils.c b/src/backend/executor/execUtils.c
index 2de056e1df4..cb11f4fc367 100644
--- a/src/backend/executor/execUtils.c
+++ b/src/backend/executor/execUtils.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/execUtils.c,v 1.107 2003/11/29 19:51:48 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/execUtils.c,v 1.108 2003/12/18 20:21:37 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -18,6 +18,7 @@
  *		FreeExecutorState
  *		CreateExprContext
  *		FreeExprContext
+ *		ReScanExprContext
  *
  *		ExecAssignExprContext	Common code for plan node init routines.
  *		ExecAssignResultType
@@ -352,6 +353,24 @@ FreeExprContext(ExprContext *econtext)
 	pfree(econtext);
 }
 
+/*
+ * ReScanExprContext
+ *
+ *		Reset an expression context in preparation for a rescan of its
+ *		plan node.  This requires calling any registered shutdown callbacks,
+ *		since any partially complete set-returning-functions must be canceled.
+ *
+ * Note we make no assumption about the caller's memory context.
+ */
+void
+ReScanExprContext(ExprContext *econtext)
+{
+	/* Call any registered callbacks */
+	ShutdownExprContext(econtext);
+	/* And clean up the memory used */
+	MemoryContextReset(econtext->ecxt_per_tuple_memory);
+}
+
 /*
  * Build a per-output-tuple ExprContext for an EState.
  *
diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h
index 022b759c86e..8f1dc7fafaf 100644
--- a/src/include/executor/executor.h
+++ b/src/include/executor/executor.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/executor/executor.h,v 1.103 2003/11/29 22:41:01 pgsql Exp $
+ * $PostgreSQL: pgsql/src/include/executor/executor.h,v 1.104 2003/12/18 20:21:37 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -201,6 +201,7 @@ extern EState *CreateExecutorState(void);
 extern void FreeExecutorState(EState *estate);
 extern ExprContext *CreateExprContext(EState *estate);
 extern void FreeExprContext(ExprContext *econtext);
+extern void ReScanExprContext(ExprContext *econtext);
 
 #define ResetExprContext(econtext) \
 	MemoryContextReset((econtext)->ecxt_per_tuple_memory)