diff options
| author | Amit Kapila | 2020-04-16 05:14:03 +0000 |
|---|---|---|
| committer | Amit Kapila | 2020-04-16 05:25:02 +0000 |
| commit | 24d2d38b1eb86c0b410ad0f07f66566a83c6f05c (patch) | |
| tree | a3d35fbbfc7f14e9b65b0f4a44f1acf6776809e8 /doc/src/sgml/ref/vacuum.sgml | |
| parent | 542d7817f774ea9d94798eb95cdf250d4f1527d9 (diff) | |
Fix the usage of parallel and full options of vacuum command.
Earlier we were inconsistent in allowing the usage of parallel and
full options. Change it such that we disallow them only when they are
combined in a way that we don't support.
In passing, improve the comments in some of the existing tests of parallel
vacuum.
Reported-by: Tushar Ahuja
Author: Justin Pryzby, Amit Kapila
Reviewed-by: Sawada Masahiko, Michael Paquier, Mahendra Singh Thalor and
Amit Kapila
Discussion: https://postgr.es/m/58c8d171-e665-6fa3-a9d3-d9423b694dae%40enterprisedb.com
Diffstat (limited to 'doc/src/sgml/ref/vacuum.sgml')
| -rw-r--r-- | doc/src/sgml/ref/vacuum.sgml | 32 |
1 files changed, 16 insertions, 16 deletions
diff --git a/doc/src/sgml/ref/vacuum.sgml b/doc/src/sgml/ref/vacuum.sgml index 442977a50d5..a48f75ad7ba 100644 --- a/doc/src/sgml/ref/vacuum.sgml +++ b/doc/src/sgml/ref/vacuum.sgml @@ -235,22 +235,22 @@ VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ ANALYZE ] [ <replaceable class="paramet Perform index vacuum and index cleanup phases of <command>VACUUM</command> in parallel using <replaceable class="parameter">integer</replaceable> background workers (for the details of each vacuum phase, please - refer to <xref linkend="vacuum-phases"/>). If the - <literal>PARALLEL</literal> option is omitted, then the number of workers - is determined based on the number of indexes that support parallel vacuum - operation on the relation, and is further limited by <xref - linkend="guc-max-parallel-workers-maintenance"/>. - An index can participate in parallel vacuum if and only if the size - of the index is more than <xref linkend="guc-min-parallel-index-scan-size"/>. - Please note that it is not guaranteed that the number of parallel workers - specified in <replaceable class="parameter">integer</replaceable> will - be used during execution. It is possible for a vacuum to run with fewer - workers than specified, or even with no workers at all. Only one worker - can be used per index. So parallel workers are launched only when there - are at least <literal>2</literal> indexes in the table. Workers for - vacuum are launched before the start of each phase and exit at the end of - the phase. These behaviors might change in a future release. This - option can't be used with the <literal>FULL</literal> option. + refer to <xref linkend="vacuum-phases"/>). In plain <command>VACUUM</command> + (without <literal>FULL</literal>), if the <literal>PARALLEL</literal> option + is omitted, then the number of workers is determined based on the number of + indexes on the relation that support parallel vacuum operation and is further + limited by <xref linkend="guc-max-parallel-workers-maintenance"/>. An index + can participate in parallel vacuum if and only if the size of the index is + more than <xref linkend="guc-min-parallel-index-scan-size"/>. Please note + that it is not guaranteed that the number of parallel workers specified in + <replaceable class="parameter">integer</replaceable> will be used during + execution. It is possible for a vacuum to run with fewer workers than + specified, or even with no workers at all. Only one worker can be used per + index. So parallel workers are launched only when there are at least + <literal>2</literal> indexes in the table. Workers for vacuum are launched + before the start of each phase and exit at the end of the phase. These + behaviors might change in a future release. This option can't be used with + the <literal>FULL</literal> option. </para> </listitem> </varlistentry> |