diff options
| author | Amit Kapila <akapila@postgresql.org> | 2019-09-19 08:41:05 +0530 |
|---|---|---|
| committer | Amit Kapila <akapila@postgresql.org> | 2019-09-19 08:53:19 +0530 |
| commit | 4a9b83e1cdaf811d659dffcbe7dff7ddb479e014 (patch) | |
| tree | 968e1583b018c621f14b4855f10ff42d91906412 /doc/src | |
| parent | 5431458f4a72961a81b7a62d2f8a379aea31414c (diff) | |
Doc: document autovacuum interruption.
It's important users be able to know (without looking at the source code)
that running DDL or DDL-like commands can interrupt autovacuum which can
lead to a lot of dead tuples and hence slower database operations.
Reported-by: James Coleman
Author: James Coleman
Reviewed-by: Amit Kapila
Backpatch-through: 9.4
Discussion: https://postgr.es/m/CAAaqYe-XYyNwML1=f=gnd0qWg46PnvD=BDrCZ5-L94B887XVxQ@mail.gmail.com
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/maintenance.sgml | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml index 40f9a7652ea..0e7b45371c0 100644 --- a/doc/src/sgml/maintenance.sgml +++ b/doc/src/sgml/maintenance.sgml @@ -825,6 +825,26 @@ analyze threshold = analyze base threshold + analyze scale factor * number of tu <literal>autovacuum_vacuum_cost_limit</> storage parameters have been set are not considered in the balancing algorithm. </para> + + <para> + Autovacuum workers generally don't block other commands. If a process + attempts to acquire a lock that conficts with the + <literal>SHARE UPDATE EXCLUSIVE</literal> lock held by autovacuum, lock + acquisition will interrupt the autovacuum. For conflicting lock modes, + see <xref linkend="table-lock-compatibility">. However, if the autovacuum + is running to prevent transaction ID wraparound (i.e., the autovacuum query + name in the <structname>pg_stat_activity</structname> view ends with + <literal>(to prevent wraparound)</literal>), the autovacuum is not + automatically interrupted. + </para> + + <warning> + <para> + Regularly running commands that acquire locks conflicting with a + <literal>SHARE UPDATE EXCLUSIVE</literal> lock (e.g., ANALYZE) can + effectively prevent autovacuums from ever completing. + </para> + </warning> </sect2> </sect1> |