[tiny doc fix] statistics are not retained across immediate shutdown

Started by Tsunakawa, Takayukiover 12 years ago5 messages

Tsunakawa, Takayuki

tsunakawa.takay@jp.fujitsu.com

over 12 years ago

1 attachment(s)

Hi,

In the following page, statistics are kept across server restarts:

http://www.postgresql.org/docs/current/static/monitoring-stats.html

"When the server shuts down, a permanent copy of the statistics data is stored in the global subdirectory, so that statistics can be retained across server restarts."

However, statistics are not retained after immediate shutdown (pg_ctl stop -mi). You may say "pg_ctl stop -mi is not a shutdown but an abort, so the sentence is not wrong", but it's an "immediate shutdown" and one mode of shutdown.

I propose a tiny fix to clarify this. Please find the attached patch.

I'd like this to be backported at least 9.2. Thanks.

Regards, Takayuki Tsunakawa

Attachments:

stats_reset_in_recovery.patchapplication/octet-stream; name=stats_reset_in_recovery.patchDownload

diff -rpcd a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
*** a/doc/src/sgml/monitoring.sgml	2013-06-25 03:55:41.000000000 +0900
--- b/doc/src/sgml/monitoring.sgml	2013-09-03 16:12:05.000000000 +0900
*************** postgres: <replaceable>user</> <replacea
*** 185,193 ****
     <filename>pg_stat_tmp</filename> by default.
     For better performance, <varname>stats_temp_directory</> can be
     pointed at a RAM-based file system, decreasing physical I/O requirements.
!    When the server shuts down, a permanent copy of the statistics
     data is stored in the <filename>global</filename> subdirectory, so that
!    statistics can be retained across server restarts.
    </para>
  
   </sect2>
--- 185,195 ----
     <filename>pg_stat_tmp</filename> by default.
     For better performance, <varname>stats_temp_directory</> can be
     pointed at a RAM-based file system, decreasing physical I/O requirements.
!    When the server shuts down cleanly, a permanent copy of the statistics
     data is stored in the <filename>global</filename> subdirectory, so that
!    statistics can be retained across server restarts.  When recovery is
!    performed at server start (e.g. after immediate shutdown, server crash,
!    and point-in-time recovery), all statistics counters are reset.
    </para>
  
   </sect2>

Tom Lane

tgl@sss.pgh.pa.us

over 12 years ago

In reply to: Tsunakawa, Takayuki (#1)

Re: [tiny doc fix] statistics are not retained across immediate shutdown

"Tsunakawa, Takayuki" <tsunakawa.takay@jp.fujitsu.com> writes:

I propose a tiny fix to clarify this. Please find the attached patch.

That's not an accurate description of what happens, though.
AFAIR, we do not throw away pg_stats files as a result of recovery.

regards, tom lane

--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers

Andres Freund

andres@2ndquadrant.com

over 12 years ago

In reply to: Tom Lane (#2)

Re: [tiny doc fix] statistics are not retained across immediate shutdown

On 2013-09-04 10:53:19 -0400, Tom Lane wrote:

"Tsunakawa, Takayuki" <tsunakawa.takay@jp.fujitsu.com> writes:

I propose a tiny fix to clarify this. Please find the attached patch.

That's not an accurate description of what happens, though.
AFAIR, we do not throw away pg_stats files as a result of recovery.

StartupXLOG() does a pgstat_reset_all() in the if (InRecovery) branch.

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services

--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers

Fujii Masao

masao.fujii@gmail.com

over 12 years ago

In reply to: Andres Freund (#3)

Re: [tiny doc fix] statistics are not retained across immediate shutdown

On Wed, Sep 4, 2013 at 11:56 PM, Andres Freund <andres@2ndquadrant.com> wrote:

On 2013-09-04 10:53:19 -0400, Tom Lane wrote:

"Tsunakawa, Takayuki" <tsunakawa.takay@jp.fujitsu.com> writes:

I propose a tiny fix to clarify this. Please find the attached patch.

That's not an accurate description of what happens, though.
AFAIR, we do not throw away pg_stats files as a result of recovery.

StartupXLOG() does a pgstat_reset_all() in the if (InRecovery) branch.

Yes. And this causes one problem that the statistics data would be reset
at the start after the clean shutdown of the standby server.

Regards,

--
Fujii Masao

--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers

Bruce Momjian

bruce@momjian.us

almost 12 years ago

In reply to: Tsunakawa, Takayuki (#1)

Re: [tiny doc fix] statistics are not retained across immediate shutdown

Applied.

---------------------------------------------------------------------------

On Wed, Sep 4, 2013 at 04:11:09AM +0000, Tsunakawa, Takayuki wrote:

Hi,

In the following page, statistics are kept across server restarts:

http://www.postgresql.org/docs/current/static/monitoring-stats.html

"When the server shuts down, a permanent copy of the statistics data is stored in the global subdirectory, so that statistics can be retained across server restarts."

However, statistics are not retained after immediate shutdown (pg_ctl stop -mi). You may say "pg_ctl stop -mi is not a shutdown but an abort, so the sentence is not wrong", but it's an "immediate shutdown" and one mode of shutdown.

I propose a tiny fix to clarify this. Please find the attached patch.

I'd like this to be backported at least 9.2. Thanks.

Regards, Takayuki Tsunakawa

diff -rpcd a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
*** a/doc/src/sgml/monitoring.sgml	2013-06-25 03:55:41.000000000 +0900
--- b/doc/src/sgml/monitoring.sgml	2013-09-03 16:12:05.000000000 +0900
*************** postgres: <replaceable>user</> <replacea
*** 185,193 ****
<filename>pg_stat_tmp</filename> by default.
For better performance, <varname>stats_temp_directory</> can be
pointed at a RAM-based file system, decreasing physical I/O requirements.
!    When the server shuts down, a permanent copy of the statistics
data is stored in the <filename>global</filename> subdirectory, so that
!    statistics can be retained across server restarts.
</para>

</sect2>
--- 185,195 ----
<filename>pg_stat_tmp</filename> by default.
For better performance, <varname>stats_temp_directory</> can be
pointed at a RAM-based file system, decreasing physical I/O requirements.
!    When the server shuts down cleanly, a permanent copy of the statistics
data is stored in the <filename>global</filename> subdirectory, so that
!    statistics can be retained across server restarts.  When recovery is
!    performed at server start (e.g. after immediate shutdown, server crash,
!    and point-in-time recovery), all statistics counters are reset.
</para>

</sect2>

--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers

--
Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ Everyone has their own god. +

--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers