Add a txn_start column to pg_stat_activity. This makes it easier to

identify long-running transactions. Since we already need to record
the transaction-start time (e.g. for now()), we don't need any
additional system calls to report this information.

Catversion bumped, initdb required.

src/backend/access/transam/xact.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.229 2006/11/23 01:14:59 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.230 2006/12/06 18:06:47 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1416,6 +1416,7 @@ StartTransaction(void)
 	 * GetCurrentTimestamp() call (which'd be expensive anyway).
 	 */
 	xactStartTimestamp = stmtStartTimestamp;
+	pgstat_report_txn_timestamp(xactStartTimestamp);
 
 	/*
 	 * initialize current transaction state fields
@@ -1628,6 +1629,7 @@ CommitTransaction(void)
 	/* smgrcommit already done */
 	AtEOXact_Files();
 	pgstat_count_xact_commit();
+	pgstat_report_txn_timestamp(0);
 
 	CurrentResourceOwner = NULL;
 	ResourceOwnerDelete(TopTransactionResourceOwner);
@@ -1994,6 +1996,7 @@ AbortTransaction(void)
 	smgrabort();
 	AtEOXact_Files();
 	pgstat_count_xact_rollback();
+	pgstat_report_txn_timestamp(0);
 
 	/*
 	 * State remains TRANS_ABORT until CleanupTransaction().

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 1.32 2006/11/24 21:18:42 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/catalog/system_views.sql,v 1.33 2006/12/06 18:06:47 neilc Exp $
  */
 
 CREATE VIEW pg_roles AS 
@@ -335,6 +335,7 @@ CREATE VIEW pg_stat_activity AS
             U.rolname AS usename, 
             pg_stat_get_backend_activity(S.backendid) AS current_query,
             pg_stat_get_backend_waiting(S.backendid) AS waiting,
+            pg_stat_get_backend_txn_start(S.backendid) AS txn_start,
             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 1.140 2006/11/21 20:59:52 tgl Exp $
+ *	$PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.141 2006/12/06 18:06:47 neilc Exp $
  * ----------
  */
 #include "postgres.h"
@@ -1355,6 +1355,7 @@ pgstat_bestart(void)
 	beentry->st_procpid = MyProcPid;
 	beentry->st_proc_start_timestamp = proc_start_timestamp;
 	beentry->st_activity_start_timestamp = 0;
+	beentry->st_txn_start_timestamp = 0;
 	beentry->st_databaseid = MyDatabaseId;
 	beentry->st_userid = userid;
 	beentry->st_clientaddr = clientaddr;
@@ -1443,6 +1444,29 @@ pgstat_report_activity(const char *cmd_str)
 	Assert((beentry->st_changecount & 1) == 0);
 }
 
+/*
+ * Set the current transaction start timestamp to the specified
+ * value. If there is no current active transaction, this is signified
+ * by 0.
+ */
+void
+pgstat_report_txn_timestamp(TimestampTz tstamp)
+{
+	volatile PgBackendStatus *beentry = MyBEEntry;
+
+	if (!pgstat_collect_querystring || !beentry)
+		return;
+
+	/*
+	 * Update my status entry, following the protocol of bumping
+	 * st_changecount before and after.  We use a volatile pointer
+	 * here to ensure the compiler doesn't try to get cute.
+	 */
+	beentry->st_changecount++;
+	beentry->st_txn_start_timestamp = tstamp;
+	beentry->st_changecount++;
+	Assert((beentry->st_changecount & 1) == 0);
+}
 
 /* ----------
  * pgstat_report_waiting() -

src/backend/utils/adt/pgstatfuncs.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/pgstatfuncs.c,v 1.34 2006/10/04 00:29:59 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/pgstatfuncs.c,v 1.35 2006/12/06 18:06:47 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -44,6 +44,7 @@ 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_txn_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);
 extern Datum pg_stat_get_backend_client_port(PG_FUNCTION_ARGS);
@@ -422,6 +423,29 @@ pg_stat_get_backend_activity_start(PG_FUNCTION_ARGS)
 	PG_RETURN_TIMESTAMPTZ(result);
 }
 
+
+Datum
+pg_stat_get_backend_txn_start(PG_FUNCTION_ARGS)
+{
+	int32		beid = PG_GETARG_INT32(0);
+	TimestampTz 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_txn_start_timestamp;
+
+	if (result == 0)			/* not in a transaction */
+		PG_RETURN_NULL();
+
+	PG_RETURN_TIMESTAMPTZ(result);
+}
+
+
 Datum
 pg_stat_get_backend_start(PG_FUNCTION_ARGS)
 {