doc: Improve consistency of parallel vacuum description.

Use consistent phrasing for parallel vacuum descriptions between
manual VACUUM and autovacuum. Specifically, clarify that the parallel
worker count is limited by the respective options only if they are
explicitly specified.

Also, fix a typo in the parallel vacuum section.

Author: Aleksander Alekseev <aleksander@tigerdata.com>
Discussion: https://postgr.es/m/CAJ7c6TPcSqzhbhrsiCMmVwmE8F7pwS7i9J49SP1zPKS_ER+vcA@mail.gmail.com

diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml
index 652b291de15a90ef92aa633f1ed04eb2633d6356..76262df0502c2f81d5ad1e2352622948d693fd54 100644 (file)
--- a/doc/src/sgml/maintenance.sgml
+++ b/doc/src/sgml/maintenance.sgml
@@ -1186,15 +1186,15 @@ analyze threshold = analyze base threshold + analyze scale factor * number of tu
     vacuum phase, please refer to <xref linkend="vacuum-phases"/>).  The
     degree of parallelism is determined by the number of indexes on the
     relation that support parallel vacuum.  For manual <command>VACUUM</command>,
-    this is limited by the <literal>PARALLEL</literal> option, which is
-    further capped by <xref linkend="guc-max-parallel-maintenance-workers"/>.
+    this is limited by the <literal>PARALLEL</literal> option if specified,
+    which is further capped by <xref linkend="guc-max-parallel-maintenance-workers"/>.
     For autovacuum, it is limited by the table's
-    <xref linkend="reloption-autovacuum-parallel-workers"/> if any which is
-    capped limited by
-    <xref linkend="guc-autovacuum-max-parallel-workers"/> parameter.  Please
-    note that it is not guaranteed that the number of parallel workers that was
-    calculated 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.
+    <xref linkend="reloption-autovacuum-parallel-workers"/> if specified,
+    which is further capped by <xref linkend="guc-autovacuum-max-parallel-workers"/>
+    parameter. Please note that it is not guaranteed that the number of parallel
+    workers that was calculated 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.
    </para>
 
    <para>