Wiki / Configuration Parameters

Setting commit_delay adds a time delay 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 that additional transactions become ready to commit within the given interval. However, it also increases latency by up to the commit_delay for each WAL flush. Because the delay is just wasted if no other transactions become ready to commit, a delay is only performed if at least commit_siblings other transactions are active when a flush is about to be initiated. Also, no delays are performed if fsync is disabled. If this value is specified without units, it is taken as microseconds. The default commit_delay is zero (no delay). Only superusers and users with the appropriate SET privilege can change this setting. In PostgreSQL releases prior to 9.3, commit_delay behaved differently and was much less effective: it affected only commits, rather than all WAL flushes, and waited for the entire configured delay even if the WAL flush was completed sooner. Beginning in 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 operation.

English manual coverage begins with PostgreSQL 7.4. Source history and runtime observations have their own recorded version boundaries.

boot val

0

category

Write-Ahead Log / Settings

context

superuser

documented

true

enumvals

Unknown

extra desc

Unknown

lang

en

max val

100000

metadata version

18

min val

0

name

commit_delay

short desc

Sets the delay in microseconds between transaction commit and flushing WAL to disk.

source

pg-settings-source-snapshot

unit

Unknown

vartype

integer