Re: doc review for parallel vacuum

On Tue, Apr 07, 2020 at 09:57:46AM +0530, Amit Kapila wrote:
> On Mon, Mar 23, 2020 at 10:34 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
> > On Sun, Mar 22, 2020 at 7:48 AM Justin Pryzby <pryzby@telsasoft.com> wrote:
> > >
> > > Original, long thread
> > > https://www.postgresql.org/message-id/flat/CAA4eK1%2Bnw1FBK3_sDnW%2B7kB%2Bx4qbDJqetgqwYW8k2xv82RZ%2BKw%40mail.gmail.com#b1745ee853b137043e584b500b41300f
> > >
> >
> > I have comments/questions on the patches:
> > doc changes
> > -------------------------
> > 1.
> >       <para>
> > -      Perform vacuum index and cleanup index phases of <command>VACUUM</command>
> > +      Perform vacuum index and index cleanup phases of <command>VACUUM</command>
> >
> > Why is the proposed text improvement over what is already there?
> 
> I have kept the existing text as it is for this case.

Probably it should say "index vacuum and index cleanup", which is also what the
comment in vacuumlazy.c says.

> > 2.
> > If the
> > -      <literal>PARALLEL</literal> option is omitted, then
> > -      <command>VACUUM</command> decides the number of workers based on number
> > -      of indexes that support parallel vacuum operation on the relation which
> > -      is further limited by <xref
> > linkend="guc-max-parallel-workers-maintenance"/>.
> > -      The index can participate in a parallel vacuum if and only if the size
> > +      <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"/>.
> >
> > Here, it is not clear to me why the proposed text is better than what
> > we already have?
> Changed as per your suggestion.

To answer your question:

"VACUUM decides" doesn't sound consistent with docs.

"based on {+the+} number"
=> here, you're veritably missing an article...

"relation which" technically means that the *relation* is "is further limited
by"...

> > Patch changes
> > -------------------------
> > 1.
> > - * and index cleanup with parallel workers unless the parallel vacuum is
> > + * and index cleanup with parallel workers unless parallel vacuum is
> >
> > As per my understanding 'parallel vacuum' is a noun phrase, so we
> > should have a determiner before it.
> 
> Changed as per your suggestion.

Thanks (I think you meant an "article").

> > - * We allow each worker to update it as and when it has incurred any cost and
> > + * We allow each worker to update it AS AND WHEN it has incurred any cost and
> >
> > I don't see why it is necessary to make this part bold?  We are using
> > it at one other place in the code in the way it is used here.
> >
> 
> Kept the existing text as it is.

I meant this as a question.  I'm not sure what "as and when means" ?  "If and
when" ?

> I have combined both of your patches.  Let me know if you have any
> more suggestions, otherwise, I am planning to push this tomorrow.

In the meantime, I found some more issues, so I rebased on top of your patch so
you can review it.

-- 
Justin