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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2001-02-26 00:50:08 +0000 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2001-02-26 00:50:08 +0000 |
| commit | 9c9936587c6a9aeb8b425a499cf73e5e7af38ddd (patch) | |
| tree | f1d7328907a9ffb8a9319b689a9bb40f7e1d0313 /doc/src | |
| parent | 60774e821060dd6d6395504d4ccda107d2a71a42 (diff) | |
| download | postgresql-9c9936587c6a9aeb8b425a499cf73e5e7af38ddd.tar.gz postgresql-9c9936587c6a9aeb8b425a499cf73e5e7af38ddd.zip | |
Implement COMMIT_SIBLINGS parameter to allow pre-commit delay to occur
only if at least N other backends currently have open transactions. This
is not a great deal of intelligence about whether a delay might be
profitable ... but it beats no intelligence at all. Note that the default
COMMIT_DELAY is still zero --- this new code does nothing unless that
setting is changed.
Also, mark ENABLEFSYNC as a system-wide setting. It's no longer safe to
allow that to be set per-backend, since we may be relying on some other
backend's fsync to have synced the WAL log.
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/wal.sgml | 13 |
1 files changed, 8 insertions, 5 deletions
diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml index 00f0c459ace..e706ee271c6 100644 --- a/doc/src/sgml/wal.sgml +++ b/doc/src/sgml/wal.sgml @@ -1,4 +1,4 @@ -<!-- $Header: /cvsroot/pgsql/doc/src/sgml/wal.sgml,v 1.2 2001/02/18 04:50:43 tgl Exp $ --> +<!-- $Header: /cvsroot/pgsql/doc/src/sgml/wal.sgml,v 1.3 2001/02/26 00:50:07 tgl Exp $ --> <chapter id="wal"> <title>Write-Ahead Logging (<acronym>WAL</acronym>)</title> @@ -295,10 +295,13 @@ record to the log with <function>LogInsert</function> but before performing a <function>LogFlush</function>. This delay allows other backends to add their commit records to the log so as to have all - of them flushed with a single log sync. Unfortunately, this - mechanism is not fully implemented at release 7.1, so there is at - present usually no benefit to be gained from increasing this parameter - above its default value of zero. + of them flushed with a single log sync. No sleep will occur if fsync + is not enabled or if fewer than <varname>COMMIT_SIBLINGS</varname> + other backends are not currently in active transactions; this avoids + sleeping when it's unlikely that any other backend will commit soon. + Note that on most platforms, the resolution of a sleep request is + ten milliseconds, so that any nonzero <varname>COMMIT_DELAY</varname> + setting between 1 and 10000 microseconds will have the same effect. </para> </sect1> </chapter> |