index d95c218d39c6c4ca14bc4b1435bc504431bedafc..aee8ff2dfbe53b84a2d6047c6248f39458788361 100644 (file)
@@ -825,6 +825,26 @@ analyze threshold = analyze base threshold + analyze scale factor * number of tu
<literal>autovacuum_vacuum_cost_limit</literal> 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>