Re: doc fixes: vacuum_cleanup_index_scale_factor

Hi, Justin!

Thank you for revising documentation patch.

On Mon, May 7, 2018 at 7:55 PM, Justin Pryzby <pryzby@telsasoft.com> wrote:

> On Mon, May 07, 2018 at 07:26:25PM +0300, Alexander Korotkov wrote:
> > Hi!
> >
> > I've revised docs and comments, and also made some fixes in the code.
> > See the attached patchset.
> >
> > * 0004-btree-cleanup-docs-comments-fixes.patch
> > Documentation and comment improvements from Justin Pryzby
> > revised by me.
>
> 2nd iteration:
>
> diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
> index eabe2a9235..785ecf922a 100644
> --- a/doc/src/sgml/config.sgml
> +++ b/doc/src/sgml/config.sgml
> @@ -1893,15 +1893,35 @@ include_dir 'conf.d'
>        </term>
>        <listitem>
>         <para>
> -        When no tuples were deleted from the heap, B-tree indexes might
> still
> -        be scanned during <command>VACUUM</command> cleanup stage by two
> -        reasons.  The first reason is that B-tree index contains deleted
> pages
> -        which can be recycled during cleanup.  The second reason is that
> B-tree
> -        index statistics is stalled.  The criterion of stalled index
> statistics
> -        is number of inserted tuples since previous statistics collection
> -        is greater than <varname>vacuum_cleanup_index_
> scale_factor</varname>
> -        fraction of total number of heap tuples.
> +        When no tuples were deleted from the heap, B-tree indexes are
> still
> +        scanned during <command>VACUUM</command> cleanup stage unless two
> +        conditions are met: the index contains no deleted pages which can
> be
> +        recycled during cleanup; and, the index statistics are not stale.
> +        In order to detect stale index statistics, number of total heap
> tuples
> should say: "THE number"
>
> +        during previous statistics collection is memorized in the index
> s/memorized/stored/
>
> +        meta-page.  Once number number of inserted tuples since previous
> Should say "Once the number of inserted tuples..."
>
> +        statistics collection is more than
> +        <varname>vacuum_cleanup_index_scale_factor</varname> fraction of
> +        number of heap tuples memorized in the meta-page, index
> statistics is
> s/memorized/stored/
>
> +        considered to be stalled.  Note, that number of heap tuples is
> written
> "THE number"
> s/stalled/stale/
>
> +        to the meta-page at the first time when no dead tuples are found
> remove "at"
>
> +        during <command>VACUUM</command> cycle.  Thus, skip of B-tree
> index
> I think should say: "Thus, skipping of the B-tree index scan"
>
> +        scan during cleanup stage is only possible in second and
> subsequent
> s/in/when/
>
> +       <para>
> +        Zero value of <varname>vacuum_cleanup_index_
> scale_factor</varname>
> I would say "A zero value of ..."
>

I've applied all the changes you suggested.  Please, find it in the
attached patchset.

------
Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company