Horton

Re: Unhappy about API changes in the no-fsm-for-small-rels patch

John Naylor <john.naylor@2ndquadrant.com>

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From: John Naylor <john.naylor@2ndquadrant.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Dilip Kumar <dilipbalaut@gmail.com>, Andres Freund <andres@anarazel.de>, Tom Lane <tgl@sss.pgh.pa.us>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2019-05-01T04:08:09Z
Lists: pgsql-hackers 
On Tue, Apr 30, 2019 at 6:06 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Tue, Apr 30, 2019 at 2:24 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
> >
> >  insert into atacc1 values (21, 22, 23);
> > +ERROR:  could not read block 0 in file "base/16384/31379": read only
> > 0 of 8192 bytes
> >
> > I have analysed this failure.  Seems that we have not reset the
> > rel->fsm_local_map while truncating the relation pages by vacuum
> > (lazy_truncate_heap). So when next time while accessing it we are
> > getting the error.   I think we need a mechanism to invalidate this
> > when we truncate the relation pages.   I am not sure whether we should
> > invalidate the relcache entry here or just reset the
> > rel->fsm_local_map?
> >
>
> Thanks, this appears to be the missing case where we need to
> invalidate the cache.  So, as discussed above if we issue invalidation
> call (in RecordPageWithFreeSpace) when the page becomes empty, then we
> shouldn't encounter this.  John, can we try this out and see if the
> failure goes away?

I added a clear/inval call in RecordPageWithFreeSpace and the failure
goes away. Thanks for the analysis, Dilip!

-- 
John Naylor                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Commits

  1. Revert "Avoid the creation of the free space map for small heap relations".

  2. Improve code comments in b0eaa4c51b.

  3. During pg_upgrade, conditionally skip transfer of FSMs.

  4. Add more tests for FSM.

  5. Fix typos in commit 8586bf7ed8.

  6. tableam: introduce table AM infrastructure.

  7. Clear the local map when not used.

  8. Doc: Update the documentation for FSM behavior for small tables.

  9. Make FSM test portable.

  10. Avoid creation of the free space map for small heap relations, take 2.