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pgstat's on-proc-exit hook has to execute after the last transaction commit
or abort within a backend; rearrange InitPostgres processing to make it so. Revealed by just-added Asserts along with ECPG regression tests (hm, I wonder why the core regression tests didn't expose it?). This possibly is another reason for missing stats updates ...
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3 files changed

+36
-18
lines changed

3 files changed

+36
-18
lines changed

‎src/backend/postmaster/pgstat.c

Lines changed: 27 additions & 15 deletions
Original file line numberDiff line numberDiff line change
@@ -13,7 +13,7 @@
1313
*
1414
* Copyright (c) 2001-2007, PostgreSQL Global Development Group
1515
*
16-
* $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.156 2007/05/27 03:50:39 tgl Exp $
16+
* $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.157 2007/05/27 05:37:49 tgl Exp $
1717
* ----------
1818
*/
1919
#include "postgres.h"
@@ -1771,28 +1771,45 @@ CreateSharedBackendStatus(void)
17711771
}
17721772

17731773

1774+
/* ----------
1775+
* pgstat_initialize() -
1776+
*
1777+
* Initialize pgstats state, and set up our on-proc-exit hook.
1778+
* Called from InitPostgres. MyBackendId must be set,
1779+
* but we must not have started any transaction yet (since the
1780+
* exit hook must run after the last transaction exit).
1781+
* ----------
1782+
*/
1783+
void
1784+
pgstat_initialize(void)
1785+
{
1786+
/* Initialize MyBEEntry */
1787+
Assert(MyBackendId >= 1 && MyBackendId <= MaxBackends);
1788+
MyBEEntry = &BackendStatusArray[MyBackendId - 1];
1789+
1790+
/* Set up a process-exit hook to clean up */
1791+
on_shmem_exit(pgstat_beshutdown_hook, 0);
1792+
}
1793+
17741794
/* ----------
17751795
* pgstat_bestart() -
17761796
*
1777-
* Initialize this backend's entry in the PgBackendStatus array,
1778-
* and set up an on-proc-exit hook that will clear it again.
1779-
* Called from InitPostgres. MyBackendId and MyDatabaseId must be set.
1797+
* Initialize this backend's entry in the PgBackendStatus array.
1798+
* Called from InitPostgres. MyDatabaseId and session userid must be set
1799+
* (hence, this cannot be combined with pgstat_initialize).
17801800
* ----------
17811801
*/
17821802
void
17831803
pgstat_bestart(void)
17841804
{
1785-
volatile PgBackendStatus *beentry;
17861805
TimestampTz proc_start_timestamp;
17871806
Oid userid;
17881807
SockAddr clientaddr;
1789-
1790-
Assert(MyBackendId >= 1 && MyBackendId <= MaxBackends);
1791-
MyBEEntry = &BackendStatusArray[MyBackendId - 1];
1808+
volatile PgBackendStatus *beentry;
17921809

17931810
/*
1794-
* To minimize the time spent modifying the entry, fetch all the needed
1795-
* data first.
1811+
* To minimize the time spent modifying the PgBackendStatus entry,
1812+
* fetch all the needed data first.
17961813
*
17971814
* If we have a MyProcPort, use its session start time (for consistency,
17981815
* and to save a kernel call).
@@ -1839,11 +1856,6 @@ pgstat_bestart(void)
18391856

18401857
beentry->st_changecount++;
18411858
Assert((beentry->st_changecount & 1) == 0);
1842-
1843-
/*
1844-
* Set up a process-exit hook to clean up.
1845-
*/
1846-
on_shmem_exit(pgstat_beshutdown_hook, 0);
18471859
}
18481860

18491861
/*

‎src/backend/utils/init/postinit.c

Lines changed: 6 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/utils/init/postinit.c,v 1.175 2007/03/13 00:33:42 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/utils/init/postinit.c,v 1.176 2007/05/27 05:37:49 tgl Exp $
1212
*
1313
*
1414
*-------------------------------------------------------------------------
@@ -435,6 +435,10 @@ InitPostgres(const char *in_dbname, Oid dboid, const char *username,
435435
/* Initialize portal manager */
436436
EnablePortalManager();
437437

438+
/* Initialize stats collection --- must happen before first xact */
439+
if (!bootstrap)
440+
pgstat_initialize();
441+
438442
/*
439443
* Set up process-exit callback to do pre-shutdown cleanup. This has to
440444
* be after we've initialized all the low-level modules like the buffer
@@ -587,7 +591,7 @@ InitPostgres(const char *in_dbname, Oid dboid, const char *username,
587591
/* initialize client encoding */
588592
InitializeClientEncoding();
589593

590-
/* initialize statistics collection for this backend */
594+
/* report this backend in the PgBackendStatus array */
591595
if (!bootstrap)
592596
pgstat_bestart();
593597

‎src/include/pgstat.h

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -5,7 +5,7 @@
55
*
66
* Copyright (c) 2001-2007, PostgreSQL Global Development Group
77
*
8-
* $PostgreSQL: pgsql/src/include/pgstat.h,v 1.59 2007/05/27 03:50:39 tgl Exp $
8+
* $PostgreSQL: pgsql/src/include/pgstat.h,v 1.60 2007/05/27 05:37:50 tgl Exp $
99
* ----------
1010
*/
1111
#ifndef PGSTAT_H
@@ -501,7 +501,9 @@ extern void pgstat_report_analyze(Oid tableoid, bool shared,
501501
PgStat_Counter livetuples,
502502
PgStat_Counter deadtuples);
503503

504+
extern void pgstat_initialize(void);
504505
extern void pgstat_bestart(void);
506+
505507
extern void pgstat_report_activity(const char *what);
506508
extern void pgstat_report_txn_timestamp(TimestampTz tstamp);
507509
extern void pgstat_report_waiting(bool waiting);

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