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.

9 files changed, 173 insertions, 18 deletions

diff --git a/src/backend/catalog/namespace.c b/src/backend/catalog/namespace.c
index 6baa9a798b5..16853b3d791 100644
--- a/src/backend/catalog/namespace.c
+++ b/src/backend/catalog/namespace.c
@@ -13,7 +13,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/catalog/namespace.c,v 1.93 2007/03/23 19:53:51 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/catalog/namespace.c,v 1.94 2007/04/12 06:53:46 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1941,6 +1941,26 @@ InitTempTableNamespace(void)
 }
 
 /*
+ * Remove all temp tables from the temporary namespace.
+ */
+void
+ResetTempTableNamespace(void)
+{
+	char		namespaceName[NAMEDATALEN];
+	Oid			namespaceId;
+
+	/* find oid */
+	snprintf(namespaceName, sizeof(namespaceName), "pg_temp_%d", MyBackendId);
+	namespaceId = GetSysCacheOid(NAMESPACENAME,
+								 CStringGetDatum(namespaceName),
+								 0, 0, 0);
+
+	/* clean if exists */
+	if (OidIsValid(namespaceId))
+		RemoveTempRelations(namespaceId);
+}
+
+/*
  * End-of-transaction cleanup for namespaces.
  */
 void
diff --git a/src/backend/commands/async.c b/src/backend/commands/async.c
index f96ff139643..55b99f8c922 100644
--- a/src/backend/commands/async.c
+++ b/src/backend/commands/async.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/async.c,v 1.135 2007/01/05 22:19:25 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/async.c,v 1.136 2007/04/12 06:53:46 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -127,7 +127,6 @@ static bool unlistenExitRegistered = false;
 bool		Trace_notify = false;
 
 
-static void Async_UnlistenAll(void);
 static void Async_UnlistenOnExit(int code, Datum arg);
 static void ProcessIncomingNotify(void);
 static void NotifyMyFrontEnd(char *relname, int32 listenerPID);
@@ -335,7 +334,7 @@ Async_Unlisten(const char *relname)
  *
  *--------------------------------------------------------------
  */
-static void
+void
 Async_UnlistenAll(void)
 {
 	Relation	lRel;
diff --git a/src/backend/commands/portalcmds.c b/src/backend/commands/portalcmds.c
index 98b200d2cff..d759ed4ac2d 100644
--- a/src/backend/commands/portalcmds.c
+++ b/src/backend/commands/portalcmds.c
@@ -14,7 +14,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/portalcmds.c,v 1.62 2007/03/13 00:33:39 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/portalcmds.c,v 1.63 2007/04/12 06:53:46 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -236,11 +236,18 @@ PerformPortalClose(const char *name)
 {
 	Portal		portal;
 
+	/* NULL means CLOSE ALL */
+	if (name == NULL)
+	{
+		PortalHashTableDeleteAll();
+		return;
+	}
+
 	/*
 	 * Disallow empty-string cursor name (conflicts with protocol-level
 	 * unnamed portal).
 	 */
-	if (!name || name[0] == '\0')
+	if (name[0] == '\0')
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_CURSOR_NAME),
 				 errmsg("invalid cursor name: must not be empty")));
diff --git a/src/backend/commands/prepare.c b/src/backend/commands/prepare.c
index 2c284cb9be0..fe1a8532f07 100644
--- a/src/backend/commands/prepare.c
+++ b/src/backend/commands/prepare.c
@@ -10,7 +10,7 @@
  * Copyright (c) 2002-2007, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/prepare.c,v 1.70 2007/03/13 00:33:39 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/prepare.c,v 1.71 2007/04/12 06:53:46 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -575,7 +575,10 @@ FetchPreparedStatementTargetList(PreparedStatement *stmt)
 void
 DeallocateQuery(DeallocateStmt *stmt)
 {
-	DropPreparedStatement(stmt->name, true);
+	if (stmt->name)
+		DropPreparedStatement(stmt->name, true);
+	else
+		DropAllPreparedStatements();
 }
 
 /*
@@ -602,6 +605,31 @@ DropPreparedStatement(const char *stmt_name, bool showError)
 }
 
 /*
+ * Drop all cached statements.
+ */
+void
+DropAllPreparedStatements(void)
+{
+	HASH_SEQ_STATUS seq;
+	PreparedStatement *entry;
+
+	/* nothing cached */
+	if (!prepared_queries)
+		return;
+
+	/* walk over cache */
+	hash_seq_init(&seq, prepared_queries);
+	while ((entry = hash_seq_search(&seq)) != NULL)
+	{
+		/* Release the plancache entry */
+		DropCachedPlan(entry->plansource);
+
+		/* Now we can remove the hash table entry */
+		hash_search(prepared_queries, entry->stmt_name, HASH_REMOVE, NULL);
+	}
+}
+
+/*
  * Implements the 'EXPLAIN EXECUTE' utility statement.
  */
 void
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 56278f56e5d..6aa81eec3ef 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.587 2007/04/08 00:26:34 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.588 2007/04/12 06:53:46 neilc Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -1667,6 +1667,12 @@ ClosePortalStmt:
 					n->portalname = $2;
 					$$ = (Node *)n;
 				}
+			| CLOSE ALL
+				{
+					ClosePortalStmt *n = makeNode(ClosePortalStmt);
+					n->portalname = NULL;
+					$$ = (Node *)n;
+				}
 		;
 
 
@@ -5591,6 +5597,18 @@ DeallocateStmt: DEALLOCATE name
 						n->name = $3;
 						$$ = (Node *) n;
 					}
+				| DEALLOCATE ALL
+					{
+						DeallocateStmt *n = makeNode(DeallocateStmt);
+						n->name = NULL;
+						$$ = (Node *) n;
+					}
+				| DEALLOCATE PREPARE ALL
+					{
+						DeallocateStmt *n = makeNode(DeallocateStmt);
+						n->name = NULL;
+						$$ = (Node *) n;
+					}
 		;
 
 /*****************************************************************************
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 864b6d1dd63..88adb625d55 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/tcop/utility.c,v 1.276 2007/04/02 03:49:39 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/tcop/utility.c,v 1.277 2007/04/12 06:53:47 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -990,7 +990,7 @@ ProcessUtility(Node *parsetree,
 			{
 				VariableResetStmt *n = (VariableResetStmt *) parsetree;
 
-				ResetPGVariable(n->name);
+				ResetPGVariable(n->name, isTopLevel);
 			}
 			break;
 
@@ -1387,7 +1387,13 @@ CreateCommandTag(Node *parsetree)
 			break;
 
 		case T_ClosePortalStmt:
-			tag = "CLOSE CURSOR";
+			{
+				ClosePortalStmt *stmt = (ClosePortalStmt *) parsetree;
+				if (stmt->portalname == NULL)
+					tag = "CLOSE CURSOR ALL";
+				else
+					tag = "CLOSE CURSOR";
+			}
 			break;
 
 		case T_FetchStmt:
@@ -1746,7 +1752,13 @@ CreateCommandTag(Node *parsetree)
 			break;
 
 		case T_VariableResetStmt:
-			tag = "RESET";
+			{
+				VariableResetStmt *stmt = (VariableResetStmt *) parsetree;
+				if (pg_strcasecmp(stmt->name, "session") == 0)
+					tag = "RESET SESSION";
+				else
+					tag = "RESET";
+			}
 			break;
 
 		case T_CreateTrigStmt:
@@ -1856,7 +1868,13 @@ CreateCommandTag(Node *parsetree)
 			break;
 
 		case T_DeallocateStmt:
-			tag = "DEALLOCATE";
+			{
+				DeallocateStmt *stmt = (DeallocateStmt *) parsetree;
+				if (stmt->name == NULL)
+					tag = "DEALLOCATE ALL";
+				else
+					tag = "DEALLOCATE";
+			}
 			break;
 
 		/* already-planned queries */
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 $
  *
  *-------------------------------------------------------------------------
  */
@@ -881,6 +881,15 @@ PlanCacheCallback(Datum arg, Oid relid)
 }
 
 /*
+ * ResetPlanCache: drop all cached plans.
+ */
+void
+ResetPlanCache(void)
+{
+	PlanCacheCallback((Datum) 0, InvalidOid);
+}
+
+/*
  * ScanQueryForRelids callback function for PlanCacheCallback
  */
 static void
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"
@@ -4952,13 +4954,44 @@ GetPGVariableResultDesc(const char *name)
 }
 
 /*
+ * 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.