Add a 'waiting' column to pg_stat_activity to carry the same information

that ps_status provides by appending 'waiting' to the PS display.  This
completes the project of making it feasible to turn off process title
updates and instead rely on pg_stat_activity.  Per my suggestion a few
weeks ago.

src/backend/catalog/system_views.sql

@@ -3,7 +3,7 @@
  *
  * Copyright (c) 1996-2006, PostgreSQL Global Development Group
  *
- * $PostgreSQL: pgsql/src/backend/catalog/system_views.sql,v 1.29 2006/07/27 08:30:41 petere Exp $
+ * $PostgreSQL: pgsql/src/backend/catalog/system_views.sql,v 1.30 2006/08/19 01:36:24 tgl Exp $
  */
 
 CREATE VIEW pg_roles AS 
@@ -332,7 +332,8 @@ CREATE VIEW pg_stat_activity AS
             pg_stat_get_backend_pid(S.backendid) AS procpid, 
             pg_stat_get_backend_userid(S.backendid) AS usesysid, 
             U.rolname AS usename, 
-            pg_stat_get_backend_activity(S.backendid) AS current_query, 
+            pg_stat_get_backend_activity(S.backendid) AS current_query,
+            pg_stat_get_backend_waiting(S.backendid) AS waiting,
             pg_stat_get_backend_activity_start(S.backendid) AS query_start,
             pg_stat_get_backend_start(S.backendid) AS backend_start,
             pg_stat_get_backend_client_addr(S.backendid) AS client_addr,

src/backend/postmaster/pgstat.c

@@ -13,7 +13,7 @@
  *
  *	Copyright (c) 2001-2006, PostgreSQL Global Development Group
  *
- *	$PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.136 2006/07/16 18:17:14 tgl Exp $
+ *	$PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.137 2006/08/19 01:36:24 tgl Exp $
  * ----------
  */
 #include "postgres.h"
@@ -1358,6 +1358,7 @@ pgstat_bestart(void)
 	beentry->st_databaseid = MyDatabaseId;
 	beentry->st_userid = userid;
 	beentry->st_clientaddr = clientaddr;
+	beentry->st_waiting = false;
 	beentry->st_activity[0] = '\0';
 	/* Also make sure the last byte in the string area is always 0 */
 	beentry->st_activity[PGBE_ACTIVITY_SIZE - 1] = '\0';
@@ -1445,6 +1446,31 @@ pgstat_report_activity(const char *cmd_str)
 }
 
 
+/* ----------
+ * pgstat_report_waiting() -
+ *
+ *	Called from lock manager to report beginning or end of a lock wait.
+ * ----------
+ */
+void
+pgstat_report_waiting(bool waiting)
+{
+	volatile PgBackendStatus *beentry;
+
+	if (!pgstat_collect_querystring)
+		return;
+
+	/*
+	 * Since this is a single-byte field in a struct that only this process
+	 * may modify, there seems no need to bother with the st_changecount
+	 * protocol.  The update must appear atomic in any case.
+	 */
+	beentry = MyBEEntry;
+
+	beentry->st_waiting = waiting;
+}
+
+
 /* ----------
  * pgstat_read_current_status() -
  *

src/backend/storage/lmgr/lock.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/lmgr/lock.c,v 1.170 2006/07/31 20:09:05 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/lmgr/lock.c,v 1.171 2006/08/19 01:36:28 tgl Exp $
  *
  * NOTES
  *	  A lock table is a shared memory hash table.  When
@@ -36,6 +36,7 @@
 #include "access/twophase.h"
 #include "access/twophase_rmgr.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "storage/lmgr.h"
 #include "utils/memutils.h"
 #include "utils/ps_status.h"
@@ -1114,6 +1115,7 @@ WaitOnLock(LOCALLOCK *locallock, ResourceOwner owner)
 	LOCK_PRINT("WaitOnLock: sleeping on lock",
 			   locallock->lock, locallock->tag.mode);
 
+	/* Report change to waiting status */
 	if (update_process_title)
 	{
 		old_status = get_ps_display(&len);
@@ -1123,7 +1125,8 @@ WaitOnLock(LOCALLOCK *locallock, ResourceOwner owner)
 		set_ps_display(new_status, false);
 		new_status[len] = '\0';		/* truncate off " waiting" */
 	}
-	
+	pgstat_report_waiting(true);
+
 	awaitedLock = locallock;
 	awaitedOwner = owner;
 
@@ -1160,11 +1163,13 @@ WaitOnLock(LOCALLOCK *locallock, ResourceOwner owner)
 
 	awaitedLock = NULL;
 
+	/* Report change to non-waiting status */
 	if (update_process_title)
 	{
 		set_ps_display(new_status, false);
 		pfree(new_status);
 	}
+	pgstat_report_waiting(false);
 
 	LOCK_PRINT("WaitOnLock: wakeup on lock",
 			   locallock->lock, locallock->tag.mode);

src/backend/utils/adt/pgstatfuncs.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/pgstatfuncs.c,v 1.32 2006/07/14 14:52:24 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/pgstatfuncs.c,v 1.33 2006/08/19 01:36:29 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -42,6 +42,7 @@ extern Datum pg_stat_get_backend_pid(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_backend_dbid(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_backend_userid(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_backend_activity(PG_FUNCTION_ARGS);
+extern Datum pg_stat_get_backend_waiting(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_backend_activity_start(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_backend_start(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_backend_client_addr(PG_FUNCTION_ARGS);
@@ -377,6 +378,25 @@ pg_stat_get_backend_activity(PG_FUNCTION_ARGS)
 }
 
 
+Datum
+pg_stat_get_backend_waiting(PG_FUNCTION_ARGS)
+{
+	int32		beid = PG_GETARG_INT32(0);
+	bool		result;
+	PgBackendStatus *beentry;
+
+	if ((beentry = pgstat_fetch_stat_beentry(beid)) == NULL)
+		PG_RETURN_NULL();
+
+	if (!superuser() && beentry->st_userid != GetUserId())
+		PG_RETURN_NULL();
+
+	result = beentry->st_waiting;
+
+	PG_RETURN_BOOL(result);
+}
+
+
 Datum
 pg_stat_get_backend_activity_start(PG_FUNCTION_ARGS)
 {