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Fujii Masao d8735b8b46 Fix issues in pg_stat_wal.
1) Previously there were both pgstat_send_wal() and pgstat_report_wal()
   in order to send WAL activity to the stats collector. With the former being
   used by wal writer, the latter by most other processes. They were a bit
   redundant and so this commit merges them into pgstat_send_wal() to
   simplify the code.

2) Previously WAL global statistics counters were calculated and then
   compared with zero-filled buffer in order to determine whether any WAL
   activity has happened since the last submission. These calculation and
   comparison were not cheap. This was regularly exercised even in read-only
   workloads. This commit fixes the issue by making some WAL activity
   counters directly be checked to determine if there's WAL activity stats
   to send.

3) Previously pgstat_report_stat() did not check if there's WAL activity
   stats to send as part of the "Don't expend a clock check if nothing to do"
   check at the top. It's probably rare to have pending WAL stats without
   also passing one of the other conditions, but for safely this commit
   changes pgstat_report_stats() so that it checks also some WAL activity
   counters at the top.

This commit also adds the comments about the design of WAL stats.

Reported-by: Andres Freund
Author: Masahiro Ikeda
Reviewed-by: Kyotaro Horiguchi, Atsushi Torikoshi, Andres Freund, Fujii Masao
Discussion: https://postgr.es/m/20210324232224.vrfiij2rxxwqqjjb@alap3.anarazel.de
2021-05-19 11:38:34 +09:00
config Update config.guess and config.sub 2021-04-21 16:33:40 +02:00
contrib Allow compute_query_id to be set to 'auto' and make it default 2021-05-15 14:13:09 -04:00
doc Add --no-toast-compression to pg_dumpall 2021-05-19 09:38:48 +09:00
src Fix issues in pg_stat_wal. 2021-05-19 11:38:34 +09:00
.dir-locals.el Make Emacs perl-mode indent more like perltidy. 2019-01-13 11:32:31 -08:00
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.gitignore Support for optimizing and emitting code in LLVM JIT provider. 2018-03-22 11:05:22 -07:00
aclocal.m4 Remove configure-time probe for DocBook DTD. 2020-11-30 15:24:13 -05:00
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COPYRIGHT Update copyright for 2021 2021-01-02 13:06:25 -05:00
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PostgreSQL Database Management System
=====================================

This directory contains the source code distribution of the PostgreSQL
database management system.

PostgreSQL is an advanced object-relational database management system
that supports an extended subset of the SQL standard, including
transactions, foreign keys, subqueries, triggers, user-defined types
and functions.  This distribution also contains C language bindings.

PostgreSQL has many language interfaces, many of which are listed here:

	https://www.postgresql.org/download/

See the file INSTALL for instructions on how to build and install
PostgreSQL.  That file also lists supported operating systems and
hardware platforms and contains information regarding any other
software packages that are required to build or run the PostgreSQL
system.  Copyright and license information can be found in the
file COPYRIGHT.  A comprehensive documentation set is included in this
distribution; it can be read as described in the installation
instructions.

The latest version of this software may be obtained at
https://www.postgresql.org/download/.  For more information look at our
web site located at https://www.postgresql.org/.