diff options
| -rw-r--r-- | doc/src/sgml/config.sgml | 13 |
1 files changed, 8 insertions, 5 deletions
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 95de86441e4..6e1b084f71d 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -1949,7 +1949,7 @@ include 'filename' </indexterm> <listitem> <para> - <varname>commit_delay</varname> adds a time delay, set in + <varname>commit_delay</varname> adds a time delay, measured in microseconds, before a WAL flush is initiated. This can improve group commit throughput by allowing a larger number of transactions to commit via a single WAL flush, if system load is high enough @@ -1959,7 +1959,12 @@ include 'filename' flush. Because the delay is just wasted if no other transactions become ready to commit, a delay is only performed if at least <varname>commit_siblings</varname> other transactions are active - immediately before a flush would otherwise have been initiated. + when a flush is about to be initiated. Also, no delays are + performed if <varname>fsync</varname> is disabled. + The default <varname>commit_delay</> is zero (no delay). + Only superusers can change this setting. + </para> + <para> In <productname>PostgreSQL</> releases prior to 9.3, <varname>commit_delay</varname> behaved differently and was much less effective: it affected only commits, rather than all WAL flushes, @@ -1967,9 +1972,7 @@ include 'filename' was completed sooner. Beginning in <productname>PostgreSQL</> 9.3, the first process that becomes ready to flush waits for the configured interval, while subsequent processes wait only until the leader - completes the flush. The default <varname>commit_delay</> is zero - (no delay). No delays are performed unless <varname>fsync</varname> - is enabled. + completes the flush operation. </para> </listitem> </varlistentry> |