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 ...

diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index b41a16de44ce86435068597a40e0fa3537ccd08b..2870d3358548988901450c10f2c67a2a4ea0d7a9 100644 (file)
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -13,7 +13,7 @@
  *
  * Copyright (c) 2001-2007, PostgreSQL Global Development Group
  *
- * $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.156 2007/05/27 03:50:39 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.157 2007/05/27 05:37:49 tgl Exp $
  * ----------
  */
 #include "postgres.h"
@@ -1771,28 +1771,45 @@ CreateSharedBackendStatus(void)
 }
 
 
+/* ----------
+ * pgstat_initialize() -
+ *
+ * Initialize pgstats state, and set up our on-proc-exit hook.
+ * Called from InitPostgres.  MyBackendId must be set,
+ * but we must not have started any transaction yet (since the
+ * exit hook must run after the last transaction exit).
+ * ----------
+ */
+void
+pgstat_initialize(void)
+{
+   /* Initialize MyBEEntry */
+   Assert(MyBackendId >= 1 && MyBackendId <= MaxBackends);
+   MyBEEntry = &BackendStatusArray[MyBackendId - 1];
+
+   /* Set up a process-exit hook to clean up */
+   on_shmem_exit(pgstat_beshutdown_hook, 0);
+}
+
 /* ----------
  * 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.
+ * Initialize this backend's entry in the PgBackendStatus array.
+ * Called from InitPostgres.  MyDatabaseId and session userid must be set
+ * (hence, this cannot be combined with pgstat_initialize).
  * ----------
  */
 void
 pgstat_bestart(void)
 {
-   volatile PgBackendStatus *beentry;
    TimestampTz proc_start_timestamp;
    Oid         userid;
    SockAddr    clientaddr;
-
-   Assert(MyBackendId >= 1 && MyBackendId <= MaxBackends);
-   MyBEEntry = &BackendStatusArray[MyBackendId - 1];
+   volatile PgBackendStatus *beentry;
 
    /*
-    * To minimize the time spent modifying the entry, fetch all the needed
-    * data first.
+    * To minimize the time spent modifying the PgBackendStatus entry,
+    * fetch all the needed data first.
     *
     * If we have a MyProcPort, use its session start time (for consistency,
     * and to save a kernel call).
@@ -1839,11 +1856,6 @@ pgstat_bestart(void)
 
    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);
 }
 
 /*

diff --git a/src/backend/utils/init/postinit.c b/src/backend/utils/init/postinit.c
index daef3199fa6285a2848cf81783c5c39fef63ee24..ff70c8d6a66e23843ce823a07d856c3e3a838de6 100644 (file)
--- a/src/backend/utils/init/postinit.c
+++ b/src/backend/utils/init/postinit.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/backend/utils/init/postinit.c,v 1.175 2007/03/13 00:33:42 tgl Exp $
+ *   $PostgreSQL: pgsql/src/backend/utils/init/postinit.c,v 1.176 2007/05/27 05:37:49 tgl Exp $
  *
  *
  *-------------------------------------------------------------------------
@@ -435,6 +435,10 @@ InitPostgres(const char *in_dbname, Oid dboid, const char *username,
    /* Initialize portal manager */
    EnablePortalManager();
 
+   /* Initialize stats collection --- must happen before first xact */
+   if (!bootstrap)
+       pgstat_initialize();
+
    /*
     * Set up process-exit callback to do pre-shutdown cleanup.  This has to
     * 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,
    /* initialize client encoding */
    InitializeClientEncoding();
 
-   /* initialize statistics collection for this backend */
+   /* report this backend in the PgBackendStatus array */
    if (!bootstrap)
        pgstat_bestart();
 

diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 476fd47dc7b0ab48fba50abc3b4ad3e965c522ae..02010c7d89be31887ab3d6a673ec2fec3acb51f8 100644 (file)
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -5,7 +5,7 @@
  *
  * Copyright (c) 2001-2007, PostgreSQL Global Development Group
  *
- * $PostgreSQL: pgsql/src/include/pgstat.h,v 1.59 2007/05/27 03:50:39 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/pgstat.h,v 1.60 2007/05/27 05:37:50 tgl Exp $
  * ----------
  */
 #ifndef PGSTAT_H
@@ -501,7 +501,9 @@ extern void pgstat_report_analyze(Oid tableoid, bool shared,
                      PgStat_Counter livetuples,
                      PgStat_Counter deadtuples);
 
+extern void pgstat_initialize(void);
 extern void pgstat_bestart(void);
+
 extern void pgstat_report_activity(const char *what);
 extern void pgstat_report_txn_timestamp(TimestampTz tstamp);
 extern void pgstat_report_waiting(bool waiting);