From d13e903beaecd45a3721e4c2a7f9ff842ce94a79 Mon Sep 17 00:00:00 2001
From: Neil Conway
Date: Thu, 12 Apr 2007 06:53:49 +0000
Subject: RESET SESSION, plus related new DDL commands. Patch from Marko Kreen,
 reviewed by Neil Conway. This patch adds the following DDL command variants:
 RESET SESSION, RESET TEMP, RESET PLANS, CLOSE ALL, and DEALLOCATE ALL. RESET
 SESSION is intended for use by connection pool software and the like, in
 order to reset a client session to something close to its initial state.

Note that while most of these command variants can be executed
inside a transaction block (but are not transaction-aware!),
RESET SESSION cannot. While this is inconsistent, it is intended
to catch programmer mistakes: RESET SESSION in an open transaction
block is probably unintended.
---
 src/backend/utils/cache/plancache.c | 11 ++++++++++-
 src/backend/utils/misc/guc.c        | 37 +++++++++++++++++++++++++++++++++++--
 src/backend/utils/mmgr/portalmem.c  | 25 ++++++++++++++++++++++++-
 3 files changed, 69 insertions(+), 4 deletions(-)

(limited to 'src/backend/utils')

diff --git a/src/backend/utils/cache/plancache.c b/src/backend/utils/cache/plancache.c
index f02a58e29b1..6165e59c6e6 100644
--- a/src/backend/utils/cache/plancache.c
+++ b/src/backend/utils/cache/plancache.c
@@ -33,7 +33,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/cache/plancache.c,v 1.5 2007/03/26 00:36:19 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/cache/plancache.c,v 1.6 2007/04/12 06:53:47 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -880,6 +880,15 @@ PlanCacheCallback(Datum arg, Oid relid)
 	}
 }
 
+/*
+ * ResetPlanCache: drop all cached plans.
+ */
+void
+ResetPlanCache(void)
+{
+	PlanCacheCallback((Datum) 0, InvalidOid);
+}
+
 /*
  * ScanQueryForRelids callback function for PlanCacheCallback
  */
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index f921c75a60b..385411c0582 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -10,7 +10,7 @@
  * Written by Peter Eisentraut <peter_e@gmx.net>.
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.383 2007/03/19 23:38:30 wieck Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.384 2007/04/12 06:53:47 neilc Exp $
  *
  *--------------------------------------------------------------------
  */
@@ -32,6 +32,7 @@
 #include "access/xact.h"
 #include "catalog/namespace.h"
 #include "commands/async.h"
+#include "commands/prepare.h"
 #include "commands/vacuum.h"
 #include "commands/variable.h"
 #include "commands/trigger.h"
@@ -61,6 +62,7 @@
 #include "utils/memutils.h"
 #include "utils/pg_locale.h"
 #include "utils/plancache.h"
+#include "utils/portal.h"
 #include "utils/ps_status.h"
 #include "utils/tzparser.h"
 #include "utils/xml.h"
@@ -4951,14 +4953,45 @@ GetPGVariableResultDesc(const char *name)
 	return tupdesc;
 }
 
+/*
+ * RESET SESSION command.
+ */
+static void
+ResetSession(bool isTopLevel)
+{
+	/*
+	 * Disallow RESET SESSION in a transaction block. This is arguably
+	 * inconsistent (we don't make a similar check in the command
+	 * sequence that RESET SESSION is equivalent to), but the idea is
+	 * to catch mistakes: RESET SESSION inside a transaction block
+	 * would leave the transaction still uncommitted.
+	 */
+	PreventTransactionChain(isTopLevel, "RESET SESSION");
+
+	SetPGVariable("session_authorization", NIL, false);
+	ResetAllOptions();
+	DropAllPreparedStatements();
+	PortalHashTableDeleteAll();
+	Async_UnlistenAll();
+	ResetPlanCache();
+	ResetTempTableNamespace();
+}
+
 /*
  * RESET command
  */
 void
-ResetPGVariable(const char *name)
+ResetPGVariable(const char *name, bool isTopLevel)
 {
 	if (pg_strcasecmp(name, "all") == 0)
 		ResetAllOptions();
+	else if (pg_strcasecmp(name, "session") == 0)
+		ResetSession(isTopLevel);
+	else if (pg_strcasecmp(name, "temp") == 0 ||
+			 pg_strcasecmp(name, "temporary") == 0)
+		ResetTempTableNamespace();
+	else if (pg_strcasecmp(name, "plans") == 0)
+		ResetPlanCache();
 	else
 		set_config_option(name,
 						  NULL,
diff --git a/src/backend/utils/mmgr/portalmem.c b/src/backend/utils/mmgr/portalmem.c
index 043ea1e57a4..eeba207dc94 100644
--- a/src/backend/utils/mmgr/portalmem.c
+++ b/src/backend/utils/mmgr/portalmem.c
@@ -12,7 +12,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/mmgr/portalmem.c,v 1.100 2007/03/13 00:33:42 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/mmgr/portalmem.c,v 1.101 2007/04/12 06:53:48 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -452,6 +452,29 @@ PortalDrop(Portal portal, bool isTopCommit)
 	pfree(portal);
 }
 
+/*
+ * Delete all declared cursors.
+ *
+ * Used by commands: CLOSE ALL, RESET SESSION
+ */
+void
+PortalHashTableDeleteAll(void)
+{
+	HASH_SEQ_STATUS status;
+	PortalHashEnt *hentry;
+
+	if (PortalHashTable == NULL)
+		return;
+
+	hash_seq_init(&status, PortalHashTable);
+	while ((hentry = hash_seq_search(&status)) != NULL)
+	{
+		Portal portal = hentry->portal;
+		if (portal->status != PORTAL_ACTIVE)
+			PortalDrop(portal, false);
+	}
+}
+
 
 /*
  * Pre-commit processing for portals.
-- 
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