Take the statistics collector out of the loop for monitoring backends'

current commands; instead, store current-status information in shared
memory.  This substantially reduces the overhead of stats_command_string
and also ensures that pg_stat_activity is fully up to date at all times.
Per my recent proposal.

9 files changed, 697 insertions, 1040 deletions

diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index 50486f8cef2..f6949f14377 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/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 1.128 2006/06/18 15:38:37 petere Exp $
+ *	$PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.129 2006/06/19 01:51:21 tgl Exp $
  * ----------
  */
 #include "postgres.h"
@@ -84,7 +84,6 @@
  * ----------
  */
 #define PGSTAT_DB_HASH_SIZE		16
-#define PGSTAT_BE_HASH_SIZE		512
 #define PGSTAT_TAB_HASH_SIZE	512
 
 
@@ -94,9 +93,9 @@
  */
 bool		pgstat_collect_startcollector = true;
 bool		pgstat_collect_resetonpmstart = false;
-bool		pgstat_collect_querystring = false;
 bool		pgstat_collect_tuplelevel = false;
 bool		pgstat_collect_blocklevel = false;
+bool		pgstat_collect_querystring = false;
 
 /* ----------
  * Local data
@@ -104,13 +103,13 @@ bool		pgstat_collect_blocklevel = false;
  */
 NON_EXEC_STATIC int pgStatSock = -1;
 NON_EXEC_STATIC int pgStatPipe[2] = {-1, -1};
+
 static struct sockaddr_storage pgStatAddr;
+
 static pid_t pgStatCollectorPid = 0;
 
 static time_t last_pgstat_start_time;
 
-static long pgStatNumMessages = 0;
-
 static bool pgStatRunningInCollector = false;
 
 /*
@@ -135,8 +134,9 @@ static int	pgStatXactRollback = 0;
 
 static TransactionId pgStatDBHashXact = InvalidTransactionId;
 static HTAB *pgStatDBHash = NULL;
-static PgStat_StatBeEntry *pgStatBeTable = NULL;
-static int	pgStatNumBackends = 0;
+static TransactionId pgStatLocalStatusXact = InvalidTransactionId;
+static PgBackendStatus *localBackendStatusTable = NULL;
+static int	localNumBackends = 0;
 
 static volatile bool	need_statwrite;
 
@@ -166,21 +166,15 @@ static void pgstat_die(SIGNAL_ARGS);
 static void pgstat_beshutdown_hook(int code, Datum arg);
 
 static PgStat_StatDBEntry *pgstat_get_db_entry(Oid databaseid, bool create);
-static int	pgstat_add_backend(PgStat_MsgHdr *msg);
-static void pgstat_sub_backend(int procpid);
 static void pgstat_drop_database(Oid databaseid);
 static void pgstat_write_statsfile(void);
-static void pgstat_read_statsfile(HTAB **dbhash, Oid onlydb,
-					  PgStat_StatBeEntry **betab,
-					  int *numbackends);
+static void pgstat_read_statsfile(HTAB **dbhash, Oid onlydb);
 static void backend_read_statsfile(void);
+static void pgstat_read_current_status(void);
 
 static void pgstat_setheader(PgStat_MsgHdr *hdr, StatMsgType mtype);
 static void pgstat_send(void *msg, int len);
 
-static void pgstat_recv_bestart(PgStat_MsgBestart *msg, int len);
-static void pgstat_recv_beterm(PgStat_MsgBeterm *msg, int len);
-static void pgstat_recv_activity(PgStat_MsgActivity *msg, int len);
 static void pgstat_recv_tabstat(PgStat_MsgTabstat *msg, int len);
 static void pgstat_recv_tabpurge(PgStat_MsgTabpurge *msg, int len);
 static void pgstat_recv_dropdb(PgStat_MsgDropdb *msg, int len);
@@ -221,10 +215,11 @@ pgstat_init(void)
 #define TESTBYTEVAL ((char) 199)
 
 	/*
-	 * Force start of collector daemon if something to collect
+	 * Force start of collector daemon if something to collect.  Note that
+	 * pgstat_collect_querystring is now an independent facility that does
+	 * not require the collector daemon.
 	 */
-	if (pgstat_collect_querystring ||
-		pgstat_collect_tuplelevel ||
+	if (pgstat_collect_tuplelevel ||
 		pgstat_collect_blocklevel)
 		pgstat_collect_startcollector = true;
 
@@ -451,7 +446,6 @@ startup_failed:
 
 	/* Adjust GUC variables to suppress useless activity */
 	pgstat_collect_startcollector = false;
-	pgstat_collect_querystring = false;
 	pgstat_collect_tuplelevel = false;
 	pgstat_collect_blocklevel = false;
 }
@@ -626,52 +620,6 @@ pgstat_start(void)
 }
 
 
-/* ----------
- * pgstat_beterm() -
- *
- *	Called from postmaster to tell collector a backend terminated.
- * ----------
- */
-void
-pgstat_beterm(int pid)
-{
-	PgStat_MsgBeterm msg;
-
-	if (pgStatSock < 0)
-		return;
-
-	/* can't use pgstat_setheader() because it's not called in a backend */
-	MemSet(&(msg.m_hdr), 0, sizeof(msg.m_hdr));
-	msg.m_hdr.m_type = PGSTAT_MTYPE_BETERM;
-	msg.m_hdr.m_procpid = pid;
-
-	pgstat_send(&msg, sizeof(msg));
-}
-
-
-/* ----------
- * pgstat_report_autovac() -
- *
- *	Called from autovacuum.c to report startup of an autovacuum process.
- *	We are called before InitPostgres is done, so can't rely on MyDatabaseId;
- *	the db OID must be passed in, instead.
- * ----------
- */
-void
-pgstat_report_autovac(Oid dboid)
-{
-	PgStat_MsgAutovacStart msg;
-
-	if (pgStatSock < 0)
-		return;
-
-	pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_AUTOVAC_START);
-	msg.m_databaseid = dboid;
-	msg.m_start_time = GetCurrentTimestamp();
-
-	pgstat_send(&msg, sizeof(msg));
-}
-
 /* ------------------------------------------------------------
  * Public functions used by backends follow
  *------------------------------------------------------------
@@ -679,135 +627,6 @@ pgstat_report_autovac(Oid dboid)
 
 
 /* ----------
- * pgstat_bestart() -
- *
- *	Tell the collector that this new backend is soon ready to process
- *	queries. Called from InitPostgres.
- * ----------
- */
-void
-pgstat_bestart(void)
-{
-	PgStat_MsgBestart msg;
-
-	if (pgStatSock < 0)
-		return;
-
-	/*
-	 * We may not have a MyProcPort (eg, if this is the autovacuum process).
-	 * Send an all-zeroes client address, which is dealt with specially in
-	 * pg_stat_get_backend_client_addr and pg_stat_get_backend_client_port.
-	 */
-	pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_BESTART);
-	msg.m_databaseid = MyDatabaseId;
-	msg.m_userid = GetSessionUserId();
-	if (MyProcPort)
-		memcpy(&msg.m_clientaddr, &MyProcPort->raddr, sizeof(msg.m_clientaddr));
-	else
-		MemSet(&msg.m_clientaddr, 0, sizeof(msg.m_clientaddr));
-	pgstat_send(&msg, sizeof(msg));
-
-	/*
-	 * Set up a process-exit hook to ensure we flush the last batch of
-	 * statistics to the collector.
-	 */
-	on_shmem_exit(pgstat_beshutdown_hook, 0);
-}
-
-/* ---------
- * pgstat_report_vacuum() -
- *
- *	Tell the collector about the table we just vacuumed.
- * ---------
- */
-void
-pgstat_report_vacuum(Oid tableoid, bool shared,
-					 bool analyze, PgStat_Counter tuples)
-{
-	PgStat_MsgVacuum msg;
-
-	if (pgStatSock < 0 ||
-		!pgstat_collect_tuplelevel)
-		return;
-
-	pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_VACUUM);
-	msg.m_databaseid = shared ? InvalidOid : MyDatabaseId;
-	msg.m_tableoid = tableoid;
-	msg.m_analyze = analyze;
-	msg.m_autovacuum = IsAutoVacuumProcess(); /* is this autovacuum? */
-	msg.m_vacuumtime = GetCurrentTimestamp();
-	msg.m_tuples = tuples;
-	pgstat_send(&msg, sizeof(msg));
-}
-
-/* --------
- * pgstat_report_analyze() -
- *
- *	Tell the collector about the table we just analyzed.
- * --------
- */
-void
-pgstat_report_analyze(Oid tableoid, bool shared, PgStat_Counter livetuples,
-					  PgStat_Counter deadtuples)
-{
-	PgStat_MsgAnalyze msg;
-
-	if (pgStatSock < 0 ||
-		!pgstat_collect_tuplelevel)
-		return;
-
-	pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_ANALYZE);
-	msg.m_databaseid = shared ? InvalidOid : MyDatabaseId;
-	msg.m_tableoid = tableoid;
-	msg.m_autovacuum = IsAutoVacuumProcess(); /* is this autovacuum? */
-	msg.m_analyzetime = GetCurrentTimestamp();
-	msg.m_live_tuples = livetuples;
-	msg.m_dead_tuples = deadtuples;
-	pgstat_send(&msg, sizeof(msg));
-}
-
-/*
- * Flush any remaining statistics counts out to the collector at process
- * exit.   Without this, operations triggered during backend exit (such as
- * temp table deletions) won't be counted.
- */
-static void
-pgstat_beshutdown_hook(int code, Datum arg)
-{
-	pgstat_report_tabstat();
-}
-
-
-/* ----------
- * pgstat_report_activity() -
- *
- *	Called from tcop/postgres.c to tell the collector what the backend
- *	is actually doing (usually "<IDLE>" or the start of the query to
- *	be executed).
- * ----------
- */
-void
-pgstat_report_activity(const char *cmd_str)
-{
-	PgStat_MsgActivity msg;
-	int			len;
-
-	if (!pgstat_collect_querystring || pgStatSock < 0)
-		return;
-
-	len = strlen(cmd_str);
-	len = pg_mbcliplen(cmd_str, len, PGSTAT_ACTIVITY_SIZE - 1);
-
-	memcpy(msg.m_cmd_str, cmd_str, len);
-	msg.m_cmd_str[len] = '\0';
-	len += offsetof(PgStat_MsgActivity, m_cmd_str) + 1;
-
-	pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_ACTIVITY);
-	pgstat_send(&msg, len);
-}
-
-
-/* ----------
  * pgstat_report_tabstat() -
  *
  *	Called from tcop/postgres.c to send the so far collected
@@ -820,8 +639,7 @@ pgstat_report_tabstat(void)
 	int			i;
 
 	if (pgStatSock < 0 ||
-		(!pgstat_collect_querystring &&
-		 !pgstat_collect_tuplelevel &&
+		(!pgstat_collect_tuplelevel &&
 		 !pgstat_collect_blocklevel))
 	{
 		/* Not reporting stats, so just flush whatever we have */
@@ -1086,6 +904,83 @@ pgstat_reset_counters(void)
 
 
 /* ----------
+ * pgstat_report_autovac() -
+ *
+ *	Called from autovacuum.c to report startup of an autovacuum process.
+ *	We are called before InitPostgres is done, so can't rely on MyDatabaseId;
+ *	the db OID must be passed in, instead.
+ * ----------
+ */
+void
+pgstat_report_autovac(Oid dboid)
+{
+	PgStat_MsgAutovacStart msg;
+
+	if (pgStatSock < 0)
+		return;
+
+	pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_AUTOVAC_START);
+	msg.m_databaseid = dboid;
+	msg.m_start_time = GetCurrentTimestamp();
+
+	pgstat_send(&msg, sizeof(msg));
+}
+
+
+/* ---------
+ * pgstat_report_vacuum() -
+ *
+ *	Tell the collector about the table we just vacuumed.
+ * ---------
+ */
+void
+pgstat_report_vacuum(Oid tableoid, bool shared,
+					 bool analyze, PgStat_Counter tuples)
+{
+	PgStat_MsgVacuum msg;
+
+	if (pgStatSock < 0 ||
+		!pgstat_collect_tuplelevel)
+		return;
+
+	pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_VACUUM);
+	msg.m_databaseid = shared ? InvalidOid : MyDatabaseId;
+	msg.m_tableoid = tableoid;
+	msg.m_analyze = analyze;
+	msg.m_autovacuum = IsAutoVacuumProcess(); /* is this autovacuum? */
+	msg.m_vacuumtime = GetCurrentTimestamp();
+	msg.m_tuples = tuples;
+	pgstat_send(&msg, sizeof(msg));
+}
+
+/* --------
+ * pgstat_report_analyze() -
+ *
+ *	Tell the collector about the table we just analyzed.
+ * --------
+ */
+void
+pgstat_report_analyze(Oid tableoid, bool shared, PgStat_Counter livetuples,
+					  PgStat_Counter deadtuples)
+{
+	PgStat_MsgAnalyze msg;
+
+	if (pgStatSock < 0 ||
+		!pgstat_collect_tuplelevel)
+		return;
+
+	pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_ANALYZE);
+	msg.m_databaseid = shared ? InvalidOid : MyDatabaseId;
+	msg.m_tableoid = tableoid;
+	msg.m_autovacuum = IsAutoVacuumProcess(); /* is this autovacuum? */
+	msg.m_analyzetime = GetCurrentTimestamp();
+	msg.m_live_tuples = livetuples;
+	msg.m_dead_tuples = deadtuples;
+	pgstat_send(&msg, sizeof(msg));
+}
+
+
+/* ----------
  * pgstat_ping() -
  *
  *	Send some junk data to the collector to increase traffic.
@@ -1231,8 +1126,7 @@ pgstat_initstats(PgStat_Info *stats, Relation rel)
 void
 pgstat_count_xact_commit(void)
 {
-	if	(!pgstat_collect_querystring &&
-		 !pgstat_collect_tuplelevel &&
+	if	(!pgstat_collect_tuplelevel &&
 		 !pgstat_collect_blocklevel)
 		return;
 
@@ -1263,8 +1157,7 @@ pgstat_count_xact_commit(void)
 void
 pgstat_count_xact_rollback(void)
 {
-	if	(!pgstat_collect_querystring &&
-		 !pgstat_collect_tuplelevel &&
+	if	(!pgstat_collect_tuplelevel &&
 		 !pgstat_collect_blocklevel)
 		return;
 
@@ -1375,20 +1268,21 @@ pgstat_fetch_stat_tabentry(Oid relid)
  * pgstat_fetch_stat_beentry() -
  *
  *	Support function for the SQL-callable pgstat* functions. Returns
- *	the actual activity slot of one active backend. The caller is
- *	responsible for a check if the actual user is permitted to see
- *	that info (especially the querystring).
+ *	our local copy of the current-activity entry for one backend.
+ *
+ *	NB: caller is responsible for a check if the user is permitted to see
+ *	this info (especially the querystring).
  * ----------
  */
-PgStat_StatBeEntry *
+PgBackendStatus *
 pgstat_fetch_stat_beentry(int beid)
 {
-	backend_read_statsfile();
+	pgstat_read_current_status();
 
-	if (beid < 1 || beid > pgStatNumBackends)
+	if (beid < 1 || beid > localNumBackends)
 		return NULL;
 
-	return &pgStatBeTable[beid - 1];
+	return &localBackendStatusTable[beid - 1];
 }
 
 
@@ -1402,12 +1296,262 @@ pgstat_fetch_stat_beentry(int beid)
 int
 pgstat_fetch_stat_numbackends(void)
 {
-	backend_read_statsfile();
+	pgstat_read_current_status();
 
-	return pgStatNumBackends;
+	return localNumBackends;
 }
 
 
+/* ------------------------------------------------------------
+ * Functions for management of the shared-memory PgBackendStatus array
+ * ------------------------------------------------------------
+ */
+
+static PgBackendStatus *BackendStatusArray = NULL;
+static PgBackendStatus *MyBEEntry = NULL;
+
+
+/*
+ * Report shared-memory space needed by CreateSharedBackendStatus.
+ */
+Size
+BackendStatusShmemSize(void)
+{
+	Size		size;
+
+	size = mul_size(sizeof(PgBackendStatus), MaxBackends);
+	return size;
+}
+
+/*
+ * Initialize the shared status array during postmaster startup.
+ */
+void
+CreateSharedBackendStatus(void)
+{
+	Size		size = BackendStatusShmemSize();
+	bool		found;
+
+	/* Create or attach to the shared array */
+	BackendStatusArray = (PgBackendStatus *)
+		ShmemInitStruct("Backend Status Array", size, &found);
+
+	if (!found)
+	{
+		/*
+		 * We're the first - initialize.
+		 */
+		MemSet(BackendStatusArray, 0, size);
+	}
+}
+
+
+/* ----------
+ * pgstat_bestart() -
+ *
+ *	Initialize this backend's entry in the PgBackendStatus array,
+ *	and set up an on-proc-exit hook that will clear it again.
+ *	Called from InitPostgres.  MyBackendId and MyDatabaseId must be set.
+ * ----------
+ */
+void
+pgstat_bestart(void)
+{
+	volatile PgBackendStatus *beentry;
+	TimestampTz proc_start_timestamp;
+	Oid			userid;
+	SockAddr	clientaddr;
+
+	Assert(MyBackendId >= 1 && MyBackendId <= MaxBackends);
+	MyBEEntry = &BackendStatusArray[MyBackendId - 1];
+
+	/*
+	 * To minimize the time spent modifying the entry, fetch all the
+	 * needed data first.
+	 */
+	proc_start_timestamp = GetCurrentTimestamp();
+	userid = GetSessionUserId();
+
+	/*
+	 * We may not have a MyProcPort (eg, if this is the autovacuum process).
+	 * If so, use all-zeroes client address, which is dealt with specially in
+	 * pg_stat_get_backend_client_addr and pg_stat_get_backend_client_port.
+	 */
+	if (MyProcPort)
+		memcpy(&clientaddr, &MyProcPort->raddr, sizeof(clientaddr));
+	else
+		MemSet(&clientaddr, 0, sizeof(clientaddr));
+
+	/*
+	 * Initialize my status entry, following the protocol of bumping
+	 * st_changecount before and after; and make sure it's even afterwards.
+	 * We use a volatile pointer here to ensure the compiler doesn't try to
+	 * get cute.
+	 */
+	beentry = MyBEEntry;
+	do {
+		beentry->st_changecount++;
+	} while ((beentry->st_changecount & 1) == 0);
+
+	beentry->st_procpid = MyProcPid;
+	beentry->st_proc_start_timestamp = proc_start_timestamp;
+	beentry->st_activity_start_timestamp = 0;
+	beentry->st_databaseid = MyDatabaseId;
+	beentry->st_userid = userid;
+	beentry->st_clientaddr = clientaddr;
+	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';
+
+	beentry->st_changecount++;
+	Assert((beentry->st_changecount & 1) == 0);
+
+	/*
+	 * Set up a process-exit hook to clean up.
+	 */
+	on_shmem_exit(pgstat_beshutdown_hook, 0);
+}
+
+/*
+ * Shut down a single backend's statistics reporting at process exit.
+ *
+ * Flush any remaining statistics counts out to the collector.
+ * Without this, operations triggered during backend exit (such as
+ * temp table deletions) won't be counted.
+ *
+ * Lastly, clear out our entry in the PgBackendStatus array.
+ */
+static void
+pgstat_beshutdown_hook(int code, Datum arg)
+{
+	volatile PgBackendStatus *beentry;
+
+	pgstat_report_tabstat();
+
+	/*
+	 * Clear 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 = MyBEEntry;
+	beentry->st_changecount++;
+
+	beentry->st_procpid = 0;	/* mark invalid */
+
+	beentry->st_changecount++;
+	Assert((beentry->st_changecount & 1) == 0);
+}
+
+
+/* ----------
+ * pgstat_report_activity() -
+ *
+ *	Called from tcop/postgres.c to report what the backend is actually doing
+ *	(usually "<IDLE>" or the start of the query to be executed).
+ * ----------
+ */
+void
+pgstat_report_activity(const char *cmd_str)
+{
+	volatile PgBackendStatus *beentry;
+	TimestampTz start_timestamp;
+	int			len;
+
+	if (!pgstat_collect_querystring)
+		return;
+
+	/*
+	 * To minimize the time spent modifying the entry, fetch all the
+	 * needed data first.
+	 */
+	start_timestamp = GetCurrentTimestamp();
+
+	len = strlen(cmd_str);
+	len = pg_mbcliplen(cmd_str, len, PGBE_ACTIVITY_SIZE - 1);
+
+	/*
+	 * 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 = MyBEEntry;
+	beentry->st_changecount++;
+
+	beentry->st_activity_start_timestamp = start_timestamp;
+	memcpy((char *) beentry->st_activity, cmd_str, len);
+	beentry->st_activity[len] = '\0';
+
+	beentry->st_changecount++;
+	Assert((beentry->st_changecount & 1) == 0);
+}
+
+
+/* ----------
+ * pgstat_read_current_status() -
+ *
+ *	Copy the current contents of the PgBackendStatus array to local memory,
+ *	if not already done in this transaction.
+ * ----------
+ */
+static void
+pgstat_read_current_status(void)
+{
+	TransactionId topXid = GetTopTransactionId();
+	volatile PgBackendStatus *beentry;
+	PgBackendStatus *localentry;
+	int			i;
+
+	Assert(!pgStatRunningInCollector);
+	if (TransactionIdEquals(pgStatLocalStatusXact, topXid))
+		return;					/* already done */
+
+	localBackendStatusTable = (PgBackendStatus *)
+		MemoryContextAlloc(TopTransactionContext,
+						   sizeof(PgBackendStatus) * MaxBackends);
+	localNumBackends = 0;
+
+	beentry = BackendStatusArray;
+	localentry = localBackendStatusTable;
+	for (i = 1; i <= MaxBackends; i++)
+	{
+		/*
+		 * Follow the protocol of retrying if st_changecount changes while
+		 * we copy the entry, or if it's odd.  (The check for odd is needed
+		 * to cover the case where we are able to completely copy the entry
+		 * while the source backend is between increment steps.)  We use a
+		 * volatile pointer here to ensure the compiler doesn't try to get
+		 * cute.
+		 */
+		for (;;)
+		{
+			int		save_changecount = beentry->st_changecount;
+
+			/*
+			 * XXX if PGBE_ACTIVITY_SIZE is really large, it might be best
+			 * to use strcpy not memcpy for copying the activity string?
+			 */
+			memcpy(localentry, (char *) beentry, sizeof(PgBackendStatus));
+
+			if (save_changecount == beentry->st_changecount &&
+				(save_changecount & 1) == 0)
+				break;
+
+			/* Make sure we can break out of loop if stuck... */
+			CHECK_FOR_INTERRUPTS();
+		}
+
+		beentry++;
+		/* Only valid entries get included into the local array */
+		if (localentry->st_procpid > 0)
+		{
+			localentry++;
+			localNumBackends++;
+		}
+	}
+
+	pgStatLocalStatusXact = topXid;
+}
+
 
 /* ------------------------------------------------------------
  * Local support functions follow
@@ -1425,8 +1569,6 @@ static void
 pgstat_setheader(PgStat_MsgHdr *hdr, StatMsgType mtype)
 {
 	hdr->m_type = mtype;
-	hdr->m_backendid = MyBackendId;
-	hdr->m_procpid = MyProcPid;
 }
 
 
@@ -1613,13 +1755,7 @@ PgstatCollectorMain(int argc, char *argv[])
 	 * zero.
 	 */
 	pgStatRunningInCollector = true;
-	pgstat_read_statsfile(&pgStatDBHash, InvalidOid, NULL, NULL);
-
-	/*
-	 * Create the known backends table
-	 */
-	pgStatBeTable = (PgStat_StatBeEntry *)
-		palloc0(sizeof(PgStat_StatBeEntry) * MaxBackends);
+	pgstat_read_statsfile(&pgStatDBHash, InvalidOid);
 
 	readPipe = pgStatPipe[0];
 
@@ -1727,14 +1863,6 @@ PgstatCollectorMain(int argc, char *argv[])
 				case PGSTAT_MTYPE_DUMMY:
 					break;
 
-				case PGSTAT_MTYPE_BESTART:
-					pgstat_recv_bestart((PgStat_MsgBestart *) &msg, nread);
-					break;
-
-				case PGSTAT_MTYPE_BETERM:
-					pgstat_recv_beterm((PgStat_MsgBeterm *) &msg, nread);
-					break;
-
 				case PGSTAT_MTYPE_TABSTAT:
 					pgstat_recv_tabstat((PgStat_MsgTabstat *) &msg, nread);
 					break;
@@ -1743,10 +1871,6 @@ PgstatCollectorMain(int argc, char *argv[])
 					pgstat_recv_tabpurge((PgStat_MsgTabpurge *) &msg, nread);
 					break;
 
-				case PGSTAT_MTYPE_ACTIVITY:
-					pgstat_recv_activity((PgStat_MsgActivity *) &msg, nread);
-					break;
-
 				case PGSTAT_MTYPE_DROPDB:
 					pgstat_recv_dropdb((PgStat_MsgDropdb *) &msg, nread);
 					break;
@@ -1773,11 +1897,6 @@ PgstatCollectorMain(int argc, char *argv[])
 			}
 
 			/*
-			 * Globally count messages.
-			 */
-			pgStatNumMessages++;
-
-			/*
 			 * If this is the first message after we wrote the stats file the
 			 * last time, enable the alarm interrupt to make it be written
 			 * again later.
@@ -2066,66 +2185,6 @@ pgstat_die(SIGNAL_ARGS)
 }
 
 
-/* ----------
- * pgstat_add_backend() -
- *
- *	Support function to keep our backend list up to date.
- * ----------
- */
-static int
-pgstat_add_backend(PgStat_MsgHdr *msg)
-{
-	PgStat_StatBeEntry *beentry;
-
-	/*
-	 * Check that the backend ID is valid
-	 */
-	if (msg->m_backendid < 1 || msg->m_backendid > MaxBackends)
-	{
-		ereport(LOG,
-				(errmsg("invalid server process ID %d", msg->m_backendid)));
-		return -1;
-	}
-
-	/*
-	 * Get the slot for this backendid.
-	 */
-	beentry = &pgStatBeTable[msg->m_backendid - 1];
-
-	/*
-	 * If the slot contains the PID of this backend, everything is fine and we
-	 * have nothing to do. Note that all the slots are zero'd out when the
-	 * collector is started. We assume that a slot is "empty" iff procpid ==
-	 * 0.
-	 */
-	if (beentry->procpid > 0 && beentry->procpid == msg->m_procpid)
-		return 0;
-
-	/* Must be able to distinguish between empty and non-empty slots */
-	Assert(msg->m_procpid > 0);
-
-	/*
-	 * Put this new backend into the slot (possibly overwriting an old entry,
-	 * if we missed its BETERM or the BETERM hasn't arrived yet).
-	 */
-	beentry->procpid = msg->m_procpid;
-	beentry->start_timestamp = GetCurrentTimestamp();
-	beentry->activity_start_timestamp = 0;
-	beentry->activity[0] = '\0';
-
-	/*
-	 * We can't initialize the rest of the data in this slot until we see the
-	 * BESTART message. Therefore, we set the database and user to sentinel
-	 * values, to indicate "undefined". There is no easy way to do this for
-	 * the client address, so make sure to check that the database or user are
-	 * defined before accessing the client address.
-	 */
-	beentry->userid = InvalidOid;
-	beentry->databaseid = InvalidOid;
-
-	return 0;
-}
-
 /*
  * Lookup the hash table entry for the specified database. If no hash
  * table entry exists, initialize it, if the create parameter is true.
@@ -2171,38 +2230,6 @@ pgstat_get_db_entry(Oid databaseid, bool create)
 	return result;
 }
 
-/* ----------
- * pgstat_sub_backend() -
- *
- *	Remove a backend from the actual backends list.
- * ----------
- */
-static void
-pgstat_sub_backend(int procpid)
-{
-	int			i;
-
-	/*
-	 * Search in the known-backends table for the slot containing this PID.
-	 */
-	for (i = 0; i < MaxBackends; i++)
-	{
-		if (pgStatBeTable[i].procpid == procpid)
-		{
-			/*
-			 * That's him.  Mark the backend slot empty.
-			 */
-			pgStatBeTable[i].procpid = 0;
-			return;
-		}
-	}
-
-	/*
-	 * No big problem if not found. This can happen if UDP messages arrive out
-	 * of order here.
-	 */
-}
-
 
 /* ----------
  * pgstat_write_statsfile() -
@@ -2218,7 +2245,6 @@ pgstat_write_statsfile(void)
 	PgStat_StatDBEntry *dbentry;
 	PgStat_StatTabEntry *tabentry;
 	FILE	   *fpout;
-	int			i;
 	int32		format_id;
 
 	/*
@@ -2271,29 +2297,6 @@ pgstat_write_statsfile(void)
 	}
 
 	/*
-	 * Write out the known running backends to the stats file.
-	 */
-	i = MaxBackends;
-	fputc('M', fpout);
-	fwrite(&i, sizeof(i), 1, fpout);
-
-	for (i = 0; i < MaxBackends; i++)
-	{
-		PgStat_StatBeEntry *beentry = &pgStatBeTable[i];
-
-		if (beentry->procpid > 0)
-		{
-			int		len;
-
-			len = offsetof(PgStat_StatBeEntry, activity) +
-				strlen(beentry->activity) + 1;
-			fputc('B', fpout);
-			fwrite(&len, sizeof(len), 1, fpout);
-			fwrite(beentry, len, 1, fpout);
-		}
-	}
-
-	/*
 	 * No more output to be done. Close the temp file and replace the old
 	 * pgstat.stat with it.  The ferror() check replaces testing for error
 	 * after each individual fputc or fwrite above.
@@ -2327,43 +2330,26 @@ pgstat_write_statsfile(void)
 	}
 }
 
-/*
- * qsort/bsearch comparison routine for PIDs
- *
- * We assume PIDs are nonnegative, so there's no overflow risk
- */
-static int
-comparePids(const void *v1, const void *v2)
-{
-	return *((const int *) v1) - *((const int *) v2);
-}
 
 /* ----------
  * pgstat_read_statsfile() -
  *
- *	Reads in an existing statistics collector and initializes the
- *	databases' hash table (whose entries point to the tables' hash tables)
- *	and the current backend table.
+ *	Reads in an existing statistics collector file and initializes the
+ *	databases' hash table (whose entries point to the tables' hash tables).
  * ----------
  */
 static void
-pgstat_read_statsfile(HTAB **dbhash, Oid onlydb,
-					  PgStat_StatBeEntry **betab, int *numbackends)
+pgstat_read_statsfile(HTAB **dbhash, Oid onlydb)
 {
 	PgStat_StatDBEntry *dbentry;
 	PgStat_StatDBEntry dbbuf;
 	PgStat_StatTabEntry *tabentry;
 	PgStat_StatTabEntry tabbuf;
-	PgStat_StatBeEntry *beentry;
 	HASHCTL		hash_ctl;
 	HTAB	   *tabhash = NULL;
 	FILE	   *fpin;
 	int32		format_id;
-	int			len;
-	int			maxbackends = 0;
-	int			havebackends = 0;
 	bool		found;
-	int		   *live_pids;
 	MemoryContext use_mcxt;
 	int			mcxt_flags;
 
@@ -2373,26 +2359,16 @@ pgstat_read_statsfile(HTAB **dbhash, Oid onlydb,
 	 * TopTransactionContext instead, so the caller must only know the last
 	 * XactId when this call happened to know if his tables are still valid or
 	 * already gone!
-	 *
-	 * Also, if running in a regular backend, we check backend entries against
-	 * the PGPROC array so that we can detect stale entries.  This lets us
-	 * discard entries whose BETERM message got lost for some reason.
 	 */
 	if (pgStatRunningInCollector || IsAutoVacuumProcess())
 	{
 		use_mcxt = NULL;
 		mcxt_flags = 0;
-		live_pids = NULL;
 	}
 	else
 	{
 		use_mcxt = TopTransactionContext;
 		mcxt_flags = HASH_CONTEXT;
-		live_pids = GetAllBackendPids();
-		/* Sort the PID array so we can use bsearch */
-		if (live_pids[0] > 1)
-			qsort((void *) &live_pids[1], live_pids[0], sizeof(int),
-				  comparePids);
 	}
 
 	/*
@@ -2407,15 +2383,6 @@ pgstat_read_statsfile(HTAB **dbhash, Oid onlydb,
 						  HASH_ELEM | HASH_FUNCTION | mcxt_flags);
 
 	/*
-	 * Initialize the number of known backends to zero, just in case we do a
-	 * silent error return below.
-	 */
-	if (numbackends != NULL)
-		*numbackends = 0;
-	if (betab != NULL)
-		*betab = NULL;
-
-	/*
 	 * Try to open the status file. If it doesn't exist, the backends simply
 	 * return zero for anything and the collector simply starts from scratch
 	 * with empty counters.
@@ -2472,7 +2439,6 @@ pgstat_read_statsfile(HTAB **dbhash, Oid onlydb,
 
 				memcpy(dbentry, &dbbuf, sizeof(PgStat_StatDBEntry));
 				dbentry->tables = NULL;
-				dbentry->n_backends = 0;
 
 				/*
 				 * Don't collect tables if not the requested DB (or the
@@ -2542,111 +2508,6 @@ pgstat_read_statsfile(HTAB **dbhash, Oid onlydb,
 				break;
 
 				/*
-				 * 'M'	The maximum number of backends to expect follows.
-				 */
-			case 'M':
-				if (betab == NULL || numbackends == NULL)
-					goto done;
-				if (fread(&maxbackends, 1, sizeof(maxbackends), fpin) !=
-					sizeof(maxbackends))
-				{
-					ereport(pgStatRunningInCollector ? LOG : WARNING,
-							(errmsg("corrupted pgstat.stat file")));
-					goto done;
-				}
-				if (maxbackends == 0)
-					goto done;
-
-				/*
-				 * Allocate space (in TopTransactionContext too) for the
-				 * backend table.
-				 */
-				if (use_mcxt == NULL)
-					*betab = (PgStat_StatBeEntry *)
-						palloc(sizeof(PgStat_StatBeEntry) * maxbackends);
-				else
-					*betab = (PgStat_StatBeEntry *)
-						MemoryContextAlloc(use_mcxt,
-								   sizeof(PgStat_StatBeEntry) * maxbackends);
-				break;
-
-				/*
-				 * 'B'	A PgStat_StatBeEntry follows.
-				 */
-			case 'B':
-				if (betab == NULL || numbackends == NULL || *betab == NULL)
-					goto done;
-
-				if (havebackends >= maxbackends)
-					goto done;
-
-				/* Read and validate the entry length */
-				if (fread(&len, 1, sizeof(len), fpin) != sizeof(len))
-				{
-					ereport(pgStatRunningInCollector ? LOG : WARNING,
-							(errmsg("corrupted pgstat.stat file")));
-					goto done;
-				}
-				if (len <= offsetof(PgStat_StatBeEntry, activity) ||
-					len > sizeof(PgStat_StatBeEntry))
-				{
-					ereport(pgStatRunningInCollector ? LOG : WARNING,
-							(errmsg("corrupted pgstat.stat file")));
-					goto done;
-				}
-
-				/*
-				 * Read it directly into the table.
-				 */
-				beentry = &(*betab)[havebackends];
-
-				if (fread(beentry, 1, len, fpin) != len)
-				{
-					ereport(pgStatRunningInCollector ? LOG : WARNING,
-							(errmsg("corrupted pgstat.stat file")));
-					goto done;
-				}
-
-				/*
-				 * If possible, check PID to verify still running
-				 */
-				if (live_pids &&
-					(live_pids[0] == 0 ||
-					 bsearch((void *) &beentry->procpid,
-							 (void *) &live_pids[1],
-							 live_pids[0],
-							 sizeof(int),
-							 comparePids) == NULL))
-				{
-					/*
-					 * Note: we could send a BETERM message to tell the
-					 * collector to drop the entry, but I'm a bit worried
-					 * about race conditions.  For now, just silently ignore
-					 * dead entries; they'll get recycled eventually anyway.
-					 */
-
-					/* Don't accept the entry */
-					memset(beentry, 0, sizeof(PgStat_StatBeEntry));
-					break;
-				}
-
-				/*
-				 * Count backends per database here.
-				 */
-				dbentry = (PgStat_StatDBEntry *)
-					hash_search(*dbhash,
-								&(beentry->databaseid),
-								HASH_FIND,
-								NULL);
-				if (dbentry)
-					dbentry->n_backends++;
-
-				havebackends++;
-				*numbackends = havebackends;
-
-				break;
-
-				/*
 				 * 'E'	The EOF marker of a complete stats file.
 				 */
 			case 'E':
@@ -2667,7 +2528,7 @@ done:
  * If not done for this transaction, read the statistics collector
  * stats file into some hash tables.
  *
- * Because we store the hash tables in TopTransactionContext, the result
+ * Because we store the tables in TopTransactionContext, the result
  * is good for the entire current main transaction.
  *
  * Inside the autovacuum process, the statfile is assumed to be valid
@@ -2684,8 +2545,7 @@ backend_read_statsfile(void)
 		if (pgStatDBHash)
 			return;
 		Assert(!pgStatRunningInCollector);
-		pgstat_read_statsfile(&pgStatDBHash, InvalidOid,
-							  &pgStatBeTable, &pgStatNumBackends);
+		pgstat_read_statsfile(&pgStatDBHash, InvalidOid);
 	}
 	else
 	{
@@ -2694,183 +2554,12 @@ backend_read_statsfile(void)
 		if (!TransactionIdEquals(pgStatDBHashXact, topXid))
 		{
 			Assert(!pgStatRunningInCollector);
-			pgstat_read_statsfile(&pgStatDBHash, MyDatabaseId,
-								  &pgStatBeTable, &pgStatNumBackends);
+			pgstat_read_statsfile(&pgStatDBHash, MyDatabaseId);
 			pgStatDBHashXact = topXid;
 		}
 	}
 }
 
-
-/* ----------
- * pgstat_recv_bestart() -
- *
- *	Process a backend startup message.
- * ----------
- */
-static void
-pgstat_recv_bestart(PgStat_MsgBestart *msg, int len)
-{
-	PgStat_StatBeEntry *entry;
-
-	/*
-	 * If the backend is known dead, we ignore the message -- we don't want to
-	 * update the backend entry's state since this BESTART message refers to
-	 * an old, dead backend
-	 */
-	if (pgstat_add_backend(&msg->m_hdr) != 0)
-		return;
-
-	entry = &(pgStatBeTable[msg->m_hdr.m_backendid - 1]);
-	entry->userid = msg->m_userid;
-	memcpy(&entry->clientaddr, &msg->m_clientaddr, sizeof(entry->clientaddr));
-	entry->databaseid = msg->m_databaseid;
-}
-
-
-/* ----------
- * pgstat_recv_beterm() -
- *
- *	Process a backend termination message.
- * ----------
- */
-static void
-pgstat_recv_beterm(PgStat_MsgBeterm *msg, int len)
-{
-	pgstat_sub_backend(msg->m_hdr.m_procpid);
-}
-
-/* ----------
- * pgstat_recv_autovac() -
- *
- *	Process an autovacuum signalling message.
- * ----------
- */
-static void
-pgstat_recv_autovac(PgStat_MsgAutovacStart *msg, int len)
-{
-	PgStat_StatDBEntry *dbentry;
-
-	/*
-	 * Lookup the database in the hashtable.  Don't create the entry if it
-	 * doesn't exist, because autovacuum may be processing a template
-	 * database.  If this isn't the case, the database is most likely to have
-	 * an entry already.  (If it doesn't, not much harm is done anyway --
-	 * it'll get created as soon as somebody actually uses the database.)
-	 */
-	dbentry = pgstat_get_db_entry(msg->m_databaseid, false);
-	if (dbentry == NULL)
-		return;
-
-	/*
-	 * Store the last autovacuum time in the database entry.
-	 */
-	dbentry->last_autovac_time = msg->m_start_time;
-}
-
-/* ----------
- * pgstat_recv_vacuum() -
- *
- *	Process a VACUUM message.
- * ----------
- */
-static void
-pgstat_recv_vacuum(PgStat_MsgVacuum *msg, int len)
-{
-	PgStat_StatDBEntry *dbentry;
-	PgStat_StatTabEntry *tabentry;
-
-	/*
-	 * Don't create either the database or table entry if it doesn't already
-	 * exist.  This avoids bloating the stats with entries for stuff that is
-	 * only touched by vacuum and not by live operations.
-	 */
-	dbentry = pgstat_get_db_entry(msg->m_databaseid, false);
-	if (dbentry == NULL)
-		return;
-
-	tabentry = hash_search(dbentry->tables, &(msg->m_tableoid),
-						   HASH_FIND, NULL);
-	if (tabentry == NULL)
-		return;
-
-	if (msg->m_autovacuum) 
-		tabentry->autovac_vacuum_timestamp = msg->m_vacuumtime;
-	else 
-		tabentry->vacuum_timestamp = msg->m_vacuumtime; 
-	tabentry->n_live_tuples = msg->m_tuples;
-	tabentry->n_dead_tuples = 0;
-	if (msg->m_analyze)
-	{
-		tabentry->last_anl_tuples = msg->m_tuples;
-		if (msg->m_autovacuum)
-			tabentry->autovac_analyze_timestamp = msg->m_vacuumtime;
-		else
-			tabentry->analyze_timestamp = msg->m_vacuumtime;
-	}
-}
-
-/* ----------
- * pgstat_recv_analyze() -
- *
- *	Process an ANALYZE message.
- * ----------
- */
-static void
-pgstat_recv_analyze(PgStat_MsgAnalyze *msg, int len)
-{
-	PgStat_StatDBEntry *dbentry;
-	PgStat_StatTabEntry *tabentry;
-
-	/*
-	 * Don't create either the database or table entry if it doesn't already
-	 * exist.  This avoids bloating the stats with entries for stuff that is
-	 * only touched by analyze and not by live operations.
-	 */
-	dbentry = pgstat_get_db_entry(msg->m_databaseid, false);
-	if (dbentry == NULL)
-		return;
-
-	tabentry = hash_search(dbentry->tables, &(msg->m_tableoid),
-						   HASH_FIND, NULL);
-	if (tabentry == NULL)
-		return;
-
-	if (msg->m_autovacuum) 
-		tabentry->autovac_analyze_timestamp = msg->m_analyzetime;
-	else 
-		tabentry->analyze_timestamp = msg->m_analyzetime;
-	tabentry->n_live_tuples = msg->m_live_tuples;
-	tabentry->n_dead_tuples = msg->m_dead_tuples;
-	tabentry->last_anl_tuples = msg->m_live_tuples + msg->m_dead_tuples;
-}
-
-/* ----------
- * pgstat_recv_activity() -
- *
- *	Remember what the backend is doing.
- * ----------
- */
-static void
-pgstat_recv_activity(PgStat_MsgActivity *msg, int len)
-{
-	PgStat_StatBeEntry *entry;
-
-	/*
-	 * Here we check explicitly for 0 return, since we don't want to mangle
-	 * the activity of an active backend by a delayed packet from a dead one.
-	 */
-	if (pgstat_add_backend(&msg->m_hdr) != 0)
-		return;
-
-	entry = &(pgStatBeTable[msg->m_hdr.m_backendid - 1]);
-
-	StrNCpy(entry->activity, msg->m_cmd_str, PGSTAT_ACTIVITY_SIZE);
-
-	entry->activity_start_timestamp = GetCurrentTimestamp();
-}
-
-
 /* ----------
  * pgstat_recv_tabstat() -
  *
@@ -2886,12 +2575,6 @@ pgstat_recv_tabstat(PgStat_MsgTabstat *msg, int len)
 	int			i;
 	bool		found;
 
-	/*
-	 * Make sure the backend is counted for.
-	 */
-	if (pgstat_add_backend(&msg->m_hdr) < 0)
-		return;
-
 	dbentry = pgstat_get_db_entry(msg->m_databaseid, true);
 
 	/*
@@ -2975,12 +2658,6 @@ pgstat_recv_tabpurge(PgStat_MsgTabpurge *msg, int len)
 	PgStat_StatDBEntry *dbentry;
 	int			i;
 
-	/*
-	 * Make sure the backend is counted for.
-	 */
-	if (pgstat_add_backend(&msg->m_hdr) < 0)
-		return;
-
 	dbentry = pgstat_get_db_entry(msg->m_databaseid, false);
 
 	/*
@@ -3014,12 +2691,6 @@ pgstat_recv_dropdb(PgStat_MsgDropdb *msg, int len)
 	PgStat_StatDBEntry *dbentry;
 
 	/*
-	 * Make sure the backend is counted for.
-	 */
-	if (pgstat_add_backend(&msg->m_hdr) < 0)
-		return;
-
-	/*
 	 * Lookup the database in the hashtable.
 	 */
 	dbentry = pgstat_get_db_entry(msg->m_databaseid, false);
@@ -3055,12 +2726,6 @@ pgstat_recv_resetcounter(PgStat_MsgResetcounter *msg, int len)
 	PgStat_StatDBEntry *dbentry;
 
 	/*
-	 * Make sure the backend is counted for.
-	 */
-	if (pgstat_add_backend(&msg->m_hdr) < 0)
-		return;
-
-	/*
 	 * Lookup the database in the hashtable.  Nothing to do if not there.
 	 */
 	dbentry = pgstat_get_db_entry(msg->m_databaseid, false);
@@ -3090,3 +2755,108 @@ pgstat_recv_resetcounter(PgStat_MsgResetcounter *msg, int len)
 								  &hash_ctl,
 								  HASH_ELEM | HASH_FUNCTION);
 }
+
+/* ----------
+ * pgstat_recv_autovac() -
+ *
+ *	Process an autovacuum signalling message.
+ * ----------
+ */
+static void
+pgstat_recv_autovac(PgStat_MsgAutovacStart *msg, int len)
+{
+	PgStat_StatDBEntry *dbentry;
+
+	/*
+	 * Lookup the database in the hashtable.  Don't create the entry if it
+	 * doesn't exist, because autovacuum may be processing a template
+	 * database.  If this isn't the case, the database is most likely to have
+	 * an entry already.  (If it doesn't, not much harm is done anyway --
+	 * it'll get created as soon as somebody actually uses the database.)
+	 */
+	dbentry = pgstat_get_db_entry(msg->m_databaseid, false);
+	if (dbentry == NULL)
+		return;
+
+	/*
+	 * Store the last autovacuum time in the database entry.
+	 */
+	dbentry->last_autovac_time = msg->m_start_time;
+}
+
+/* ----------
+ * pgstat_recv_vacuum() -
+ *
+ *	Process a VACUUM message.
+ * ----------
+ */
+static void
+pgstat_recv_vacuum(PgStat_MsgVacuum *msg, int len)
+{
+	PgStat_StatDBEntry *dbentry;
+	PgStat_StatTabEntry *tabentry;
+
+	/*
+	 * Don't create either the database or table entry if it doesn't already
+	 * exist.  This avoids bloating the stats with entries for stuff that is
+	 * only touched by vacuum and not by live operations.
+	 */
+	dbentry = pgstat_get_db_entry(msg->m_databaseid, false);
+	if (dbentry == NULL)
+		return;
+
+	tabentry = hash_search(dbentry->tables, &(msg->m_tableoid),
+						   HASH_FIND, NULL);
+	if (tabentry == NULL)
+		return;
+
+	if (msg->m_autovacuum) 
+		tabentry->autovac_vacuum_timestamp = msg->m_vacuumtime;
+	else 
+		tabentry->vacuum_timestamp = msg->m_vacuumtime; 
+	tabentry->n_live_tuples = msg->m_tuples;
+	tabentry->n_dead_tuples = 0;
+	if (msg->m_analyze)
+	{
+		tabentry->last_anl_tuples = msg->m_tuples;
+		if (msg->m_autovacuum)
+			tabentry->autovac_analyze_timestamp = msg->m_vacuumtime;
+		else
+			tabentry->analyze_timestamp = msg->m_vacuumtime;
+	}
+}
+
+/* ----------
+ * pgstat_recv_analyze() -
+ *
+ *	Process an ANALYZE message.
+ * ----------
+ */
+static void
+pgstat_recv_analyze(PgStat_MsgAnalyze *msg, int len)
+{
+	PgStat_StatDBEntry *dbentry;
+	PgStat_StatTabEntry *tabentry;
+
+	/*
+	 * Don't create either the database or table entry if it doesn't already
+	 * exist.  This avoids bloating the stats with entries for stuff that is
+	 * only touched by analyze and not by live operations.
+	 */
+	dbentry = pgstat_get_db_entry(msg->m_databaseid, false);
+	if (dbentry == NULL)
+		return;
+
+	tabentry = hash_search(dbentry->tables, &(msg->m_tableoid),
+						   HASH_FIND, NULL);
+	if (tabentry == NULL)
+		return;
+
+	if (msg->m_autovacuum) 
+		tabentry->autovac_analyze_timestamp = msg->m_analyzetime;
+	else 
+		tabentry->analyze_timestamp = msg->m_analyzetime;
+	tabentry->n_live_tuples = msg->m_live_tuples;
+	tabentry->n_dead_tuples = msg->m_dead_tuples;
+	tabentry->last_anl_tuples = msg->m_live_tuples + msg->m_dead_tuples;
+}
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index fc4a9bcdc33..aac116b466a 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -37,7 +37,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.486 2006/06/18 15:38:37 petere Exp $
+ *	  $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.487 2006/06/19 01:51:21 tgl Exp $
  *
  * NOTES
  *
@@ -2109,9 +2109,6 @@ reaper(SIGNAL_ARGS)
 		{
 			AutoVacPID = 0;
 			autovac_stopped();
-			/* Tell the collector about process termination */
-			pgstat_beterm(pid);
-
 			if (exitstatus != 0)
 				HandleChildCrash(pid, exitstatus,
 								 _("autovacuum process"));
@@ -2252,8 +2249,6 @@ CleanupBackend(int pid,
 #ifdef EXEC_BACKEND
 			ShmemBackendArrayRemove(pid);
 #endif
-			/* Tell the collector about backend termination */
-			pgstat_beterm(pid);
 			break;
 		}
 	}
@@ -2299,8 +2294,6 @@ HandleChildCrash(int pid, int exitstatus, const char *procname)
 #ifdef EXEC_BACKEND
 			ShmemBackendArrayRemove(pid);
 #endif
-			/* Tell the collector about backend termination */
-			pgstat_beterm(pid);
 			/* Keep looping so we can signal remaining backends */
 		}
 		else
diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c
index 872a33ff16b..4beba862de7 100644
--- a/src/backend/storage/ipc/ipci.c
+++ b/src/backend/storage/ipc/ipci.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/ipc/ipci.c,v 1.83 2006/05/08 00:00:10 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/ipc/ipci.c,v 1.84 2006/06/19 01:51:21 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -21,6 +21,7 @@
 #include "access/twophase.h"
 #include "access/xlog.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/bgwriter.h"
 #include "postmaster/postmaster.h"
 #include "storage/bufmgr.h"
@@ -86,6 +87,7 @@ CreateSharedMemoryAndSemaphores(bool makePrivate, int port)
 		size = add_size(size, MultiXactShmemSize());
 		size = add_size(size, LWLockShmemSize());
 		size = add_size(size, ProcArrayShmemSize());
+		size = add_size(size, BackendStatusShmemSize());
 		size = add_size(size, SInvalShmemSize());
 		size = add_size(size, FreeSpaceShmemSize());
 		size = add_size(size, BgWriterShmemSize());
@@ -167,6 +169,7 @@ CreateSharedMemoryAndSemaphores(bool makePrivate, int port)
 	if (!IsUnderPostmaster)
 		InitProcGlobal();
 	CreateSharedProcArray();
+	CreateSharedBackendStatus();
 
 	/*
 	 * Set up shared-inval messaging
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index 1cee032b524..f899b7a0e81 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -23,7 +23,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.11 2006/03/05 15:58:37 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.12 2006/06/19 01:51:21 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -733,42 +733,6 @@ IsBackendPid(int pid)
 }
 
 /*
- * GetAllBackendPids -- get an array of all current backends' PIDs
- *
- * The result is a palloc'd array with the number of active backends in
- * entry [0], their PIDs in entries [1] .. [n].  The caller must bear in
- * mind that the result may already be obsolete when returned.
- */
-int *
-GetAllBackendPids(void)
-{
-	int		   *result;
-	int			npids;
-	ProcArrayStruct *arrayP = procArray;
-	int			index;
-
-	result = (int *) palloc((MaxBackends + 1) * sizeof(int));
-	npids = 0;
-
-	LWLockAcquire(ProcArrayLock, LW_SHARED);
-
-	for (index = 0; index < arrayP->numProcs; index++)
-	{
-		PGPROC	   *proc = arrayP->procs[index];
-
-		if (proc->pid != 0)		/* ignore dummy procs */
-			result[++npids] = proc->pid;
-	}
-
-	LWLockRelease(ProcArrayLock);
-
-	Assert(npids <= MaxBackends);
-
-	result[0] = npids;
-	return result;
-}
-
-/*
  * CountActiveBackends --- count backends (other than myself) that are in
  *		active transactions.  This is used as a heuristic to decide if
  *		a pre-XLOG-flush delay is worthwhile during commit.
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index eaf379389e4..dc03beec4de 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/pgstatfuncs.c,v 1.29 2006/05/19 19:08:26 alvherre Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/pgstatfuncs.c,v 1.30 2006/06/19 01:51:21 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -61,11 +61,9 @@ extern Datum pg_stat_get_db_blocks_hit(PG_FUNCTION_ARGS);
 Datum
 pg_stat_get_numscans(PG_FUNCTION_ARGS)
 {
-	PgStat_StatTabEntry *tabentry;
-	Oid			relid;
+	Oid			relid = PG_GETARG_OID(0);
 	int64		result;
-
-	relid = PG_GETARG_OID(0);
+	PgStat_StatTabEntry *tabentry;
 
 	if ((tabentry = pgstat_fetch_stat_tabentry(relid)) == NULL)
 		result = 0;
@@ -79,11 +77,9 @@ pg_stat_get_numscans(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_tuples_returned(PG_FUNCTION_ARGS)
 {
-	PgStat_StatTabEntry *tabentry;
-	Oid			relid;
+	Oid			relid = PG_GETARG_OID(0);
 	int64		result;
-
-	relid = PG_GETARG_OID(0);
+	PgStat_StatTabEntry *tabentry;
 
 	if ((tabentry = pgstat_fetch_stat_tabentry(relid)) == NULL)
 		result = 0;
@@ -97,11 +93,9 @@ pg_stat_get_tuples_returned(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_tuples_fetched(PG_FUNCTION_ARGS)
 {
-	PgStat_StatTabEntry *tabentry;
-	Oid			relid;
+	Oid			relid = PG_GETARG_OID(0);
 	int64		result;
-
-	relid = PG_GETARG_OID(0);
+	PgStat_StatTabEntry *tabentry;
 
 	if ((tabentry = pgstat_fetch_stat_tabentry(relid)) == NULL)
 		result = 0;
@@ -115,11 +109,9 @@ pg_stat_get_tuples_fetched(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_tuples_inserted(PG_FUNCTION_ARGS)
 {
-	PgStat_StatTabEntry *tabentry;
-	Oid			relid;
+	Oid			relid = PG_GETARG_OID(0);
 	int64		result;
-
-	relid = PG_GETARG_OID(0);
+	PgStat_StatTabEntry *tabentry;
 
 	if ((tabentry = pgstat_fetch_stat_tabentry(relid)) == NULL)
 		result = 0;
@@ -133,11 +125,9 @@ pg_stat_get_tuples_inserted(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_tuples_updated(PG_FUNCTION_ARGS)
 {
-	PgStat_StatTabEntry *tabentry;
-	Oid			relid;
+	Oid			relid = PG_GETARG_OID(0);
 	int64		result;
-
-	relid = PG_GETARG_OID(0);
+	PgStat_StatTabEntry *tabentry;
 
 	if ((tabentry = pgstat_fetch_stat_tabentry(relid)) == NULL)
 		result = 0;
@@ -151,11 +141,9 @@ pg_stat_get_tuples_updated(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_tuples_deleted(PG_FUNCTION_ARGS)
 {
-	PgStat_StatTabEntry *tabentry;
-	Oid			relid;
+	Oid			relid = PG_GETARG_OID(0);
 	int64		result;
-
-	relid = PG_GETARG_OID(0);
+	PgStat_StatTabEntry *tabentry;
 
 	if ((tabentry = pgstat_fetch_stat_tabentry(relid)) == NULL)
 		result = 0;
@@ -169,11 +157,9 @@ pg_stat_get_tuples_deleted(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_blocks_fetched(PG_FUNCTION_ARGS)
 {
-	PgStat_StatTabEntry *tabentry;
-	Oid			relid;
+	Oid			relid = PG_GETARG_OID(0);
 	int64		result;
-
-	relid = PG_GETARG_OID(0);
+	PgStat_StatTabEntry *tabentry;
 
 	if ((tabentry = pgstat_fetch_stat_tabentry(relid)) == NULL)
 		result = 0;
@@ -187,11 +173,9 @@ pg_stat_get_blocks_fetched(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_blocks_hit(PG_FUNCTION_ARGS)
 {
-	PgStat_StatTabEntry *tabentry;
-	Oid			relid;
+	Oid			relid = PG_GETARG_OID(0);
 	int64		result;
-
-	relid = PG_GETARG_OID(0);
+	PgStat_StatTabEntry *tabentry;
 
 	if ((tabentry = pgstat_fetch_stat_tabentry(relid)) == NULL)
 		result = 0;
@@ -204,11 +188,9 @@ pg_stat_get_blocks_hit(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_last_vacuum_time(PG_FUNCTION_ARGS)
 {
-	PgStat_StatTabEntry *tabentry;
-	Oid			relid;
+	Oid			relid = PG_GETARG_OID(0);
 	TimestampTz	result;
-
-	relid = PG_GETARG_OID(0);
+	PgStat_StatTabEntry *tabentry;
 
 	if ((tabentry = pgstat_fetch_stat_tabentry(relid)) == NULL)
 		result = 0;
@@ -224,11 +206,9 @@ pg_stat_get_last_vacuum_time(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_last_autovacuum_time(PG_FUNCTION_ARGS)
 {
-	PgStat_StatTabEntry *tabentry;
-	Oid			relid;
+	Oid			relid = PG_GETARG_OID(0);
 	TimestampTz	result;
-
-	relid = PG_GETARG_OID(0);
+	PgStat_StatTabEntry *tabentry;
 
 	if ((tabentry = pgstat_fetch_stat_tabentry(relid)) == NULL)
 		result = 0;
@@ -244,11 +224,9 @@ pg_stat_get_last_autovacuum_time(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_last_analyze_time(PG_FUNCTION_ARGS)
 {
-	PgStat_StatTabEntry *tabentry;
-	Oid			relid;
+	Oid			relid = PG_GETARG_OID(0);
 	TimestampTz	result;
-
-	relid = PG_GETARG_OID(0);
+	PgStat_StatTabEntry *tabentry;
 
 	if ((tabentry = pgstat_fetch_stat_tabentry(relid)) == NULL)
 		result = 0;
@@ -264,11 +242,9 @@ pg_stat_get_last_analyze_time(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_last_autoanalyze_time(PG_FUNCTION_ARGS)
 {
-	PgStat_StatTabEntry *tabentry;
-	Oid			relid;
+	Oid			relid = PG_GETARG_OID(0);
 	TimestampTz	result;
-
-	relid = PG_GETARG_OID(0);
+	PgStat_StatTabEntry *tabentry;
 
 	if ((tabentry = pgstat_fetch_stat_tabentry(relid)) == NULL)
 		result = 0;
@@ -342,75 +318,59 @@ pg_stat_reset(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_backend_pid(PG_FUNCTION_ARGS)
 {
-	PgStat_StatBeEntry *beentry;
-	int32		beid;
-
-	beid = PG_GETARG_INT32(0);
+	int32		beid = PG_GETARG_INT32(0);
+	PgBackendStatus *beentry;
 
 	if ((beentry = pgstat_fetch_stat_beentry(beid)) == NULL)
 		PG_RETURN_NULL();
 
-	PG_RETURN_INT32(beentry->procpid);
+	PG_RETURN_INT32(beentry->st_procpid);
 }
 
 
 Datum
 pg_stat_get_backend_dbid(PG_FUNCTION_ARGS)
 {
-	PgStat_StatBeEntry *beentry;
-	int32		beid;
-
-	beid = PG_GETARG_INT32(0);
+	int32		beid = PG_GETARG_INT32(0);
+	PgBackendStatus *beentry;
 
 	if ((beentry = pgstat_fetch_stat_beentry(beid)) == NULL)
 		PG_RETURN_NULL();
 
-	/* Not initialized yet? */
-	if (!OidIsValid(beentry->databaseid))
-		PG_RETURN_NULL();
-
-	PG_RETURN_OID(beentry->databaseid);
+	PG_RETURN_OID(beentry->st_databaseid);
 }
 
 
 Datum
 pg_stat_get_backend_userid(PG_FUNCTION_ARGS)
 {
-	PgStat_StatBeEntry *beentry;
-	int32		beid;
-
-	beid = PG_GETARG_INT32(0);
+	int32		beid = PG_GETARG_INT32(0);
+	PgBackendStatus *beentry;
 
 	if ((beentry = pgstat_fetch_stat_beentry(beid)) == NULL)
 		PG_RETURN_NULL();
 
-	/* Not initialized yet? */
-	if (!OidIsValid(beentry->userid))
-		PG_RETURN_NULL();
-
-	PG_RETURN_OID(beentry->userid);
+	PG_RETURN_OID(beentry->st_userid);
 }
 
 
 Datum
 pg_stat_get_backend_activity(PG_FUNCTION_ARGS)
 {
-	PgStat_StatBeEntry *beentry;
-	int32		beid;
-	int			len;
-	char	   *activity;
+	int32		beid = PG_GETARG_INT32(0);
 	text	   *result;
-
-	beid = PG_GETARG_INT32(0);
+	PgBackendStatus *beentry;
+	int			len;
+	const char *activity;
 
 	if ((beentry = pgstat_fetch_stat_beentry(beid)) == NULL)
 		activity = "<backend information not available>";
-	else if (!superuser() && beentry->userid != GetUserId())
+	else if (!superuser() && beentry->st_userid != GetUserId())
 		activity = "<insufficient privilege>";
-	else if (*(beentry->activity) == '\0')
+	else if (*(beentry->st_activity) == '\0')
 		activity = "<command string not enabled>";
 	else
-		activity = beentry->activity;
+		activity = beentry->st_activity;
 
 	len = strlen(activity);
 	result = palloc(VARHDRSZ + len);
@@ -426,15 +386,15 @@ pg_stat_get_backend_activity_start(PG_FUNCTION_ARGS)
 {
 	int32		beid = PG_GETARG_INT32(0);
 	TimestampTz result;
-	PgStat_StatBeEntry *beentry;
+	PgBackendStatus *beentry;
 
 	if ((beentry = pgstat_fetch_stat_beentry(beid)) == NULL)
 		PG_RETURN_NULL();
 
-	if (!superuser() && beentry->userid != GetUserId())
+	if (!superuser() && beentry->st_userid != GetUserId())
 		PG_RETURN_NULL();
 
-	result = beentry->activity_start_timestamp;
+	result = beentry->st_activity_start_timestamp;
 
 	/*
 	 * No time recorded for start of current query -- this is the case if the
@@ -451,15 +411,15 @@ pg_stat_get_backend_start(PG_FUNCTION_ARGS)
 {
 	int32		beid = PG_GETARG_INT32(0);
 	TimestampTz result;
-	PgStat_StatBeEntry *beentry;
+	PgBackendStatus *beentry;
 
 	if ((beentry = pgstat_fetch_stat_beentry(beid)) == NULL)
 		PG_RETURN_NULL();
 
-	if (!superuser() && beentry->userid != GetUserId())
+	if (!superuser() && beentry->st_userid != GetUserId())
 		PG_RETURN_NULL();
 
-	result = beentry->start_timestamp;
+	result = beentry->st_proc_start_timestamp;
 
 	if (result == 0)			/* probably can't happen? */
 		PG_RETURN_NULL();
@@ -471,31 +431,25 @@ pg_stat_get_backend_start(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_backend_client_addr(PG_FUNCTION_ARGS)
 {
-	PgStat_StatBeEntry *beentry;
+	int32		beid = PG_GETARG_INT32(0);
+	PgBackendStatus *beentry;
 	SockAddr	zero_clientaddr;
-	int32		beid;
 	char		remote_host[NI_MAXHOST];
 	int			ret;
 
-	beid = PG_GETARG_INT32(0);
-
 	if ((beentry = pgstat_fetch_stat_beentry(beid)) == NULL)
 		PG_RETURN_NULL();
 
-	/* Not initialized yet? */
-	if (!OidIsValid(beentry->userid))
-		PG_RETURN_NULL();
-
-	if (!superuser() && beentry->userid != GetUserId())
+	if (!superuser() && beentry->st_userid != GetUserId())
 		PG_RETURN_NULL();
 
 	/* A zeroed client addr means we don't know */
 	memset(&zero_clientaddr, 0, sizeof(zero_clientaddr));
-	if (memcmp(&(beentry->clientaddr), &zero_clientaddr,
+	if (memcmp(&(beentry->st_clientaddr), &zero_clientaddr,
 			   sizeof(zero_clientaddr) == 0))
 		PG_RETURN_NULL();
 
-	switch (beentry->clientaddr.addr.ss_family)
+	switch (beentry->st_clientaddr.addr.ss_family)
 	{
 		case AF_INET:
 #ifdef HAVE_IPV6
@@ -507,7 +461,8 @@ pg_stat_get_backend_client_addr(PG_FUNCTION_ARGS)
 	}
 
 	remote_host[0] = '\0';
-	ret = pg_getnameinfo_all(&beentry->clientaddr.addr, beentry->clientaddr.salen,
+	ret = pg_getnameinfo_all(&beentry->st_clientaddr.addr,
+							 beentry->st_clientaddr.salen,
 							 remote_host, sizeof(remote_host),
 							 NULL, 0,
 							 NI_NUMERICHOST | NI_NUMERICSERV);
@@ -521,31 +476,25 @@ pg_stat_get_backend_client_addr(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_backend_client_port(PG_FUNCTION_ARGS)
 {
-	PgStat_StatBeEntry *beentry;
+	int32		beid = PG_GETARG_INT32(0);
+	PgBackendStatus *beentry;
 	SockAddr	zero_clientaddr;
-	int32		beid;
 	char		remote_port[NI_MAXSERV];
 	int			ret;
 
-	beid = PG_GETARG_INT32(0);
-
 	if ((beentry = pgstat_fetch_stat_beentry(beid)) == NULL)
 		PG_RETURN_NULL();
 
-	/* Not initialized yet? */
-	if (!OidIsValid(beentry->userid))
-		PG_RETURN_NULL();
-
-	if (!superuser() && beentry->userid != GetUserId())
+	if (!superuser() && beentry->st_userid != GetUserId())
 		PG_RETURN_NULL();
 
 	/* A zeroed client addr means we don't know */
 	memset(&zero_clientaddr, 0, sizeof(zero_clientaddr));
-	if (memcmp(&(beentry->clientaddr), &zero_clientaddr,
+	if (memcmp(&(beentry->st_clientaddr), &zero_clientaddr,
 			   sizeof(zero_clientaddr) == 0))
 		PG_RETURN_NULL();
 
-	switch (beentry->clientaddr.addr.ss_family)
+	switch (beentry->st_clientaddr.addr.ss_family)
 	{
 		case AF_INET:
 #ifdef HAVE_IPV6
@@ -559,31 +508,35 @@ pg_stat_get_backend_client_port(PG_FUNCTION_ARGS)
 	}
 
 	remote_port[0] = '\0';
-	ret = pg_getnameinfo_all(&beentry->clientaddr.addr,
-							 beentry->clientaddr.salen,
+	ret = pg_getnameinfo_all(&beentry->st_clientaddr.addr,
+							 beentry->st_clientaddr.salen,
 							 NULL, 0,
 							 remote_port, sizeof(remote_port),
 							 NI_NUMERICHOST | NI_NUMERICSERV);
 	if (ret)
 		PG_RETURN_NULL();
 
-	PG_RETURN_DATUM(DirectFunctionCall1(int4in, CStringGetDatum(remote_port)));
+	PG_RETURN_DATUM(DirectFunctionCall1(int4in,
+										CStringGetDatum(remote_port)));
 }
 
 
 Datum
 pg_stat_get_db_numbackends(PG_FUNCTION_ARGS)
 {
-	PgStat_StatDBEntry *dbentry;
-	Oid			dbid;
+	Oid			dbid = PG_GETARG_OID(0);
 	int32		result;
+	int			tot_backends = pgstat_fetch_stat_numbackends();
+	int			beid;
 
-	dbid = PG_GETARG_OID(0);
+	result = 0;
+	for (beid = 1; beid <= tot_backends; beid++)
+	{
+		PgBackendStatus *beentry = pgstat_fetch_stat_beentry(beid);
 
-	if ((dbentry = pgstat_fetch_stat_dbentry(dbid)) == NULL)
-		result = 0;
-	else
-		result = (int32) (dbentry->n_backends);
+		if (beentry && beentry->st_databaseid == dbid)
+			result++;
+	}
 
 	PG_RETURN_INT32(result);
 }
@@ -592,11 +545,9 @@ pg_stat_get_db_numbackends(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_db_xact_commit(PG_FUNCTION_ARGS)
 {
-	PgStat_StatDBEntry *dbentry;
-	Oid			dbid;
+	Oid			dbid = PG_GETARG_OID(0);
 	int64		result;
-
-	dbid = PG_GETARG_OID(0);
+	PgStat_StatDBEntry *dbentry;
 
 	if ((dbentry = pgstat_fetch_stat_dbentry(dbid)) == NULL)
 		result = 0;
@@ -610,11 +561,9 @@ pg_stat_get_db_xact_commit(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_db_xact_rollback(PG_FUNCTION_ARGS)
 {
-	PgStat_StatDBEntry *dbentry;
-	Oid			dbid;
+	Oid			dbid = PG_GETARG_OID(0);
 	int64		result;
-
-	dbid = PG_GETARG_OID(0);
+	PgStat_StatDBEntry *dbentry;
 
 	if ((dbentry = pgstat_fetch_stat_dbentry(dbid)) == NULL)
 		result = 0;
@@ -628,11 +577,9 @@ pg_stat_get_db_xact_rollback(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_db_blocks_fetched(PG_FUNCTION_ARGS)
 {
-	PgStat_StatDBEntry *dbentry;
-	Oid			dbid;
+	Oid			dbid = PG_GETARG_OID(0);
 	int64		result;
-
-	dbid = PG_GETARG_OID(0);
+	PgStat_StatDBEntry *dbentry;
 
 	if ((dbentry = pgstat_fetch_stat_dbentry(dbid)) == NULL)
 		result = 0;
@@ -646,11 +593,9 @@ pg_stat_get_db_blocks_fetched(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_db_blocks_hit(PG_FUNCTION_ARGS)
 {
-	PgStat_StatDBEntry *dbentry;
-	Oid			dbid;
+	Oid			dbid = PG_GETARG_OID(0);
 	int64		result;
-
-	dbid = PG_GETARG_OID(0);
+	PgStat_StatDBEntry *dbentry;
 
 	if ((dbentry = pgstat_fetch_stat_dbentry(dbid)) == NULL)
 		result = 0;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 9ef561d4c12..8c3931c8383 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 1.321 2006/06/05 02:49:58 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.322 2006/06/19 01:51:21 tgl Exp $
  *
  *--------------------------------------------------------------------
  */
@@ -701,16 +701,6 @@ static struct config_bool ConfigureNamesBool[] =
 		false, NULL, NULL
 	},
 	{
-		{"stats_command_string", PGC_SUSET, STATS_COLLECTOR,
-			gettext_noop("Collects statistics about executing commands."),
-			gettext_noop("Enables the collection of statistics on the currently "
-					"executing command of each session, along with the time "
-						 "at which that command began execution.")
-		},
-		&pgstat_collect_querystring,
-		false, NULL, NULL
-	},
-	{
 		{"stats_row_level", PGC_SUSET, STATS_COLLECTOR,
 			gettext_noop("Collects row-level statistics on database activity."),
 			NULL
@@ -728,6 +718,17 @@ static struct config_bool ConfigureNamesBool[] =
 	},
 
 	{
+		{"stats_command_string", PGC_SUSET, STATS_COLLECTOR,
+			gettext_noop("Collects information about executing commands."),
+			gettext_noop("Enables the collection of information on the currently "
+					"executing command of each session, along with the time "
+						 "at which that command began execution.")
+		},
+		&pgstat_collect_querystring,
+		false, NULL, NULL
+	},
+
+	{
 		{"autovacuum", PGC_SIGHUP, AUTOVACUUM,
 			gettext_noop("Starts the autovacuum subprocess."),
 			NULL
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index ee5adaa2ff2..26b2be6d6ef 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -320,21 +320,21 @@
 # RUNTIME STATISTICS
 #---------------------------------------------------------------------------
 
-# - Statistics Monitoring -
-
-#log_parser_stats = off
-#log_planner_stats = off
-#log_executor_stats = off
-#log_statement_stats = off
-
 # - Query/Index Statistics Collector -
 
-#stats_start_collector = on
 #stats_command_string = off
+#stats_start_collector = on		# needed for block or row stats
 #stats_block_level = off
 #stats_row_level = off
 #stats_reset_on_server_start = off
 
+# - Statistics Monitoring -
+
+#log_parser_stats = off
+#log_planner_stats = off
+#log_executor_stats = off
+#log_statement_stats = off
+
 
 #---------------------------------------------------------------------------
 # AUTOVACUUM PARAMETERS
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0e4094bf3e9..83a45d7217f 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -5,7 +5,7 @@
  *
  *	Copyright (c) 2001-2006, PostgreSQL Global Development Group
  *
- *	$PostgreSQL: pgsql/src/include/pgstat.h,v 1.46 2006/05/30 02:35:39 momjian Exp $
+ *	$PostgreSQL: pgsql/src/include/pgstat.h,v 1.47 2006/06/19 01:51:21 tgl Exp $
  * ----------
  */
 #ifndef PGSTAT_H
@@ -16,16 +16,14 @@
 #include "utils/rel.h"
 #include "utils/timestamp.h"
 
+
 /* ----------
- * The types of backend/postmaster -> collector messages
+ * The types of backend -> collector messages
  * ----------
  */
 typedef enum StatMsgType
 {
 	PGSTAT_MTYPE_DUMMY,
-	PGSTAT_MTYPE_BESTART,
-	PGSTAT_MTYPE_BETERM,
-	PGSTAT_MTYPE_ACTIVITY,
 	PGSTAT_MTYPE_TABSTAT,
 	PGSTAT_MTYPE_TABPURGE,
 	PGSTAT_MTYPE_DROPDB,
@@ -56,8 +54,6 @@ typedef struct PgStat_MsgHdr
 {
 	StatMsgType m_type;
 	int			m_size;
-	int			m_backendid;
-	int			m_procpid;
 } PgStat_MsgHdr;
 
 /* ----------
@@ -68,6 +64,17 @@ typedef struct PgStat_MsgHdr
  */
 #define PGSTAT_MSG_PAYLOAD	(1000 - sizeof(PgStat_MsgHdr))
 
+
+/* ----------
+ * PgStat_MsgDummy				A dummy message, ignored by the collector
+ * ----------
+ */
+typedef struct PgStat_MsgDummy
+{
+	PgStat_MsgHdr m_hdr;
+} PgStat_MsgDummy;
+
+
 /* ----------
  * PgStat_TableEntry			Per-table info in a MsgTabstat
  *
@@ -96,37 +103,67 @@ typedef struct PgStat_TableEntry
 	PgStat_Counter t_blocks_hit;
 } PgStat_TableEntry;
 
+/* ----------
+ * PgStat_MsgTabstat			Sent by the backend to report table
+ *								and buffer access statistics.
+ * ----------
+ */
+#define PGSTAT_NUM_TABENTRIES  \
+	((PGSTAT_MSG_PAYLOAD - sizeof(Oid) - 3 * sizeof(int))  \
+	 / sizeof(PgStat_TableEntry))
+
+typedef struct PgStat_MsgTabstat
+{
+	PgStat_MsgHdr m_hdr;
+	Oid			m_databaseid;
+	int			m_nentries;
+	int			m_xact_commit;
+	int			m_xact_rollback;
+	PgStat_TableEntry m_entry[PGSTAT_NUM_TABENTRIES];
+} PgStat_MsgTabstat;
+
 
 /* ----------
- * PgStat_MsgDummy				A dummy message, ignored by the collector
+ * PgStat_MsgTabpurge			Sent by the backend to tell the collector
+ *								about dead tables.
  * ----------
  */
-typedef struct PgStat_MsgDummy
+#define PGSTAT_NUM_TABPURGE  \
+	((PGSTAT_MSG_PAYLOAD - sizeof(Oid) - sizeof(int))  \
+	 / sizeof(Oid))
+
+typedef struct PgStat_MsgTabpurge
 {
 	PgStat_MsgHdr m_hdr;
-	char		m_dummy[512];
-} PgStat_MsgDummy;
+	Oid			m_databaseid;
+	int			m_nentries;
+	Oid			m_tableid[PGSTAT_NUM_TABPURGE];
+} PgStat_MsgTabpurge;
+
 
 /* ----------
- * PgStat_MsgBestart			Sent by the backend on startup
+ * PgStat_MsgDropdb				Sent by the backend to tell the collector
+ *								about a dropped database
  * ----------
  */
-typedef struct PgStat_MsgBestart
+typedef struct PgStat_MsgDropdb
 {
 	PgStat_MsgHdr m_hdr;
 	Oid			m_databaseid;
-	Oid			m_userid;
-	SockAddr	m_clientaddr;
-} PgStat_MsgBestart;
+} PgStat_MsgDropdb;
+
 
 /* ----------
- * PgStat_MsgBeterm				Sent by the postmaster after backend exit
+ * PgStat_MsgResetcounter		Sent by the backend to tell the collector
+ *								to reset counters
  * ----------
  */
-typedef struct PgStat_MsgBeterm
+typedef struct PgStat_MsgResetcounter
 {
 	PgStat_MsgHdr m_hdr;
-} PgStat_MsgBeterm;
+	Oid			m_databaseid;
+} PgStat_MsgResetcounter;
+
 
 /* ----------
  * PgStat_MsgAutovacStart		Sent by the autovacuum daemon to signal
@@ -140,6 +177,7 @@ typedef struct PgStat_MsgAutovacStart
 	TimestampTz m_start_time;
 } PgStat_MsgAutovacStart;
 
+
 /* ----------
  * PgStat_MsgVacuum				Sent by the backend or autovacuum daemon
  *								after VACUUM or VACUUM ANALYZE
@@ -156,6 +194,7 @@ typedef struct PgStat_MsgVacuum
 	PgStat_Counter m_tuples;
 } PgStat_MsgVacuum;
 
+
 /* ----------
  * PgStat_MsgAnalyze			Sent by the backend or autovacuum daemon
  *								after ANALYZE
@@ -174,80 +213,6 @@ typedef struct PgStat_MsgAnalyze
 
 
 /* ----------
- * PgStat_MsgActivity			Sent by the backends when they start
- *								to parse a query.
- * ----------
- */
-#define PGSTAT_ACTIVITY_SIZE	PGSTAT_MSG_PAYLOAD
-
-typedef struct PgStat_MsgActivity
-{
-	PgStat_MsgHdr m_hdr;
-	char		m_cmd_str[PGSTAT_ACTIVITY_SIZE];
-} PgStat_MsgActivity;
-
-/* ----------
- * PgStat_MsgTabstat			Sent by the backend to report table
- *								and buffer access statistics.
- * ----------
- */
-#define PGSTAT_NUM_TABENTRIES  \
-	((PGSTAT_MSG_PAYLOAD - sizeof(Oid) - 3 * sizeof(int))  \
-	 / sizeof(PgStat_TableEntry))
-
-typedef struct PgStat_MsgTabstat
-{
-	PgStat_MsgHdr m_hdr;
-	Oid			m_databaseid;
-	int			m_nentries;
-	int			m_xact_commit;
-	int			m_xact_rollback;
-	PgStat_TableEntry m_entry[PGSTAT_NUM_TABENTRIES];
-} PgStat_MsgTabstat;
-
-/* ----------
- * PgStat_MsgTabpurge			Sent by the backend to tell the collector
- *								about dead tables.
- * ----------
- */
-#define PGSTAT_NUM_TABPURGE  \
-	((PGSTAT_MSG_PAYLOAD - sizeof(Oid) - sizeof(int))  \
-	 / sizeof(Oid))
-
-typedef struct PgStat_MsgTabpurge
-{
-	PgStat_MsgHdr m_hdr;
-	Oid			m_databaseid;
-	int			m_nentries;
-	Oid			m_tableid[PGSTAT_NUM_TABPURGE];
-} PgStat_MsgTabpurge;
-
-
-/* ----------
- * PgStat_MsgDropdb				Sent by the backend to tell the collector
- *								about a dropped database
- * ----------
- */
-typedef struct PgStat_MsgDropdb
-{
-	PgStat_MsgHdr m_hdr;
-	Oid			m_databaseid;
-} PgStat_MsgDropdb;
-
-
-/* ----------
- * PgStat_MsgResetcounter		Sent by the backend to tell the collector
- *								to reset counters
- * ----------
- */
-typedef struct PgStat_MsgResetcounter
-{
-	PgStat_MsgHdr m_hdr;
-	Oid			m_databaseid;
-} PgStat_MsgResetcounter;
-
-
-/* ----------
  * PgStat_Msg					Union over all possible messages.
  * ----------
  */
@@ -255,8 +220,6 @@ typedef union PgStat_Msg
 {
 	PgStat_MsgHdr msg_hdr;
 	PgStat_MsgDummy msg_dummy;
-	PgStat_MsgBestart msg_bestart;
-	PgStat_MsgActivity msg_activity;
 	PgStat_MsgTabstat msg_tabstat;
 	PgStat_MsgTabpurge msg_tabpurge;
 	PgStat_MsgDropdb msg_dropdb;
@@ -275,19 +238,15 @@ typedef union PgStat_Msg
  * ------------------------------------------------------------
  */
 
-#define PGSTAT_FILE_FORMAT_ID	0x01A5BC95
+#define PGSTAT_FILE_FORMAT_ID	0x01A5BC96
 
 /* ----------
  * PgStat_StatDBEntry			The collector's data per database
- *
- * Note: n_backends is not maintained within the collector.  It's computed
- * when a backend reads the stats file for use.
  * ----------
  */
 typedef struct PgStat_StatDBEntry
 {
 	Oid			databaseid;
-	int			n_backends;
 	PgStat_Counter n_xact_commit;
 	PgStat_Counter n_xact_rollback;
 	PgStat_Counter n_blocks_fetched;
@@ -303,45 +262,12 @@ typedef struct PgStat_StatDBEntry
 
 
 /* ----------
- * PgStat_StatBeEntry			The collector's data per backend
- * ----------
- */
-typedef struct PgStat_StatBeEntry
-{
-	/* An entry is non-empty iff procpid > 0 */
-	int			procpid;
-	TimestampTz start_timestamp;
-	TimestampTz activity_start_timestamp;
-
-	/*
-	 * These fields are initialized by the BESTART message. If we have
-	 * received messages from a backend before we have received its BESTART,
-	 * these fields will be uninitialized: userid and databaseid will be
-	 * InvalidOid, and clientaddr will be undefined.
-	 */
-	Oid			userid;
-	Oid			databaseid;
-	SockAddr	clientaddr;
-
-	/*
-	 * activity[] must be last in the struct, because we only write as much
-	 * of it as needed to the stats file.
-	 */
-	char		activity[PGSTAT_ACTIVITY_SIZE];
-} PgStat_StatBeEntry;
-
-
-/* ----------
  * PgStat_StatTabEntry			The collector's data per table (or index)
  * ----------
  */
 typedef struct PgStat_StatTabEntry
 {
 	Oid			tableid;
-	TimestampTz vacuum_timestamp; /* user initiated vacuum */
-	TimestampTz autovac_vacuum_timestamp; /* autovacuum initiated */
-	TimestampTz analyze_timestamp; /* user initiated */
-	TimestampTz autovac_analyze_timestamp; /* autovacuum initiated */
 
 	PgStat_Counter numscans;
 
@@ -358,27 +284,81 @@ typedef struct PgStat_StatTabEntry
 
 	PgStat_Counter blocks_fetched;
 	PgStat_Counter blocks_hit;
+
+	TimestampTz vacuum_timestamp; /* user initiated vacuum */
+	TimestampTz autovac_vacuum_timestamp; /* autovacuum initiated */
+	TimestampTz analyze_timestamp; /* user initiated */
+	TimestampTz autovac_analyze_timestamp; /* autovacuum initiated */
 } PgStat_StatTabEntry;
 
 
 /* ----------
+ * Shared-memory data structures
+ * ----------
+ */
+
+/* Max length of st_activity string ... perhaps replace with a GUC var? */
+#define PGBE_ACTIVITY_SIZE	1024
+
+/* ----------
+ * PgBackendStatus
+ *
+ * Each live backend maintains a PgBackendStatus struct in shared memory
+ * showing its current activity.  (The structs are allocated according to
+ * BackendId, but that is not critical.)  Note that the collector process
+ * has no involvement in, or even access to, these structs.
+ * ----------
+ */
+typedef struct PgBackendStatus
+{
+	/*
+	 * To avoid locking overhead, we use the following protocol: a backend
+	 * increments st_changecount before modifying its entry, and again after
+	 * finishing a modification.  A would-be reader should note the value
+	 * of st_changecount, copy the entry into private memory, then check
+	 * st_changecount again.  If the value hasn't changed, and if it's even,
+	 * the copy is valid; otherwise start over.  This makes updates cheap
+	 * while reads are potentially expensive, but that's the tradeoff we want.
+	 */
+	int			st_changecount;
+
+	/* The entry is valid iff st_procpid > 0, unused if st_procpid == 0 */
+	int			st_procpid;
+
+	/* Times of backend process start and current activity start */
+	TimestampTz st_proc_start_timestamp;
+	TimestampTz st_activity_start_timestamp;
+
+	/* Database OID, owning user's OID, connection client address */
+	Oid			st_databaseid;
+	Oid			st_userid;
+	SockAddr	st_clientaddr;
+
+	/* current command string; MUST be null-terminated */
+	char		st_activity[PGBE_ACTIVITY_SIZE];
+} PgBackendStatus;
+
+
+/* ----------
  * GUC parameters
  * ----------
  */
 extern bool pgstat_collect_startcollector;
 extern bool pgstat_collect_resetonpmstart;
-extern bool pgstat_collect_querystring;
 extern bool pgstat_collect_tuplelevel;
 extern bool pgstat_collect_blocklevel;
+extern bool pgstat_collect_querystring;
 
 
 /* ----------
  * Functions called from postmaster
  * ----------
  */
+extern Size BackendStatusShmemSize(void);
+extern void CreateSharedBackendStatus(void);
+
 extern void pgstat_init(void);
 extern int	pgstat_start(void);
-extern void pgstat_beterm(int pid);
 extern void pgstat_reset_all(void);
 
 #ifdef EXEC_BACKEND
@@ -391,21 +371,23 @@ extern void PgstatCollectorMain(int argc, char *argv[]);
  * Functions called from backends
  * ----------
  */
-extern void pgstat_bestart(void);
-
 extern void pgstat_ping(void);
-extern void pgstat_report_activity(const char *what);
+
 extern void pgstat_report_tabstat(void);
+extern void pgstat_vacuum_tabstat(void);
+extern void pgstat_drop_relation(Oid relid);
+
+extern void pgstat_reset_counters(void);
+
 extern void pgstat_report_autovac(Oid dboid);
 extern void pgstat_report_vacuum(Oid tableoid, bool shared,
 					 bool analyze, PgStat_Counter tuples);
 extern void pgstat_report_analyze(Oid tableoid, bool shared,
 					  PgStat_Counter livetuples,
 					  PgStat_Counter deadtuples);
-extern void pgstat_vacuum_tabstat(void);
-extern void pgstat_drop_relation(Oid relid);
 
-extern void pgstat_reset_counters(void);
+extern void pgstat_bestart(void);
+extern void pgstat_report_activity(const char *what);
 
 extern void pgstat_initstats(PgStat_Info *stats, Relation rel);
 
@@ -492,7 +474,7 @@ extern void pgstat_count_xact_rollback(void);
  */
 extern PgStat_StatDBEntry *pgstat_fetch_stat_dbentry(Oid dbid);
 extern PgStat_StatTabEntry *pgstat_fetch_stat_tabentry(Oid relid);
-extern PgStat_StatBeEntry *pgstat_fetch_stat_beentry(int beid);
+extern PgBackendStatus *pgstat_fetch_stat_beentry(int beid);
 extern int	pgstat_fetch_stat_numbackends(void);
 
 #endif   /* PGSTAT_H */
diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h
index a7da09a07b7..e1710701a1d 100644
--- a/src/include/storage/procarray.h
+++ b/src/include/storage/procarray.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/procarray.h,v 1.8 2006/03/05 15:59:00 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/storage/procarray.h,v 1.9 2006/06/19 01:51:22 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -29,7 +29,6 @@ extern TransactionId GetOldestXmin(bool allDbs);
 extern PGPROC *BackendPidGetProc(int pid);
 extern int	BackendXidGetPid(TransactionId xid);
 extern bool IsBackendPid(int pid);
-extern int *GetAllBackendPids(void);
 extern bool DatabaseHasActiveBackends(Oid databaseId, bool ignoreMyself);
 
 extern int	CountActiveBackends(void);