Horton

Re: WIP: Avoid creation of the free space map for small tables

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: John Naylor <john.naylor@2ndquadrant.com>
Cc: Sawada Masahiko <sawada.mshk@gmail.com>, Mithun Cy <mithun.cy@enterprisedb.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2019-01-31T05:36:52Z
Lists: pgsql-hackers

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On Wed, Jan 30, 2019 at 8:11 PM John Naylor <john.naylor@2ndquadrant.com> wrote:
>
> On Wed, Jan 30, 2019 at 2:11 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> > This is much better than the earlier version of test and there is no
> > dependency on the vacuum.  However, I feel still there is some
> > dependency on how the rows will fit in a page and we have seen some
> > related failures due to alignment stuff.  By looking at the test, I
> > can't envision any such problem, but how about if we just write some
> > simple tests where we can check that the FSM won't be created for very
> > small number of records say one or two and then when we increase the
> > records FSM gets created, here if we want, we can even use vacuum to
> > ensure FSM gets created.  Once we are sure that the main patch passes
> > all the buildfarm tests, we can extend the test to something advanced
> > as you are proposing now.  I think that will reduce the chances of
> > failure, what do you think?
>
> That's probably a good idea to limit risk. I just very basic tests
> now, and vacuum before every relation size check to make sure any FSM
> extension (whether desired or not) is invoked. Also, in my last patch
> I forgot to implement explicit checks of the block number instead of
> assuming how many rows will fit on a page. I've used a plpgsql code
> block to do this.
>

-- Extend table with enough blocks to exceed the FSM threshold
 -- FSM is created and extended to 3 blocks

The second comment line seems redundant to me, so I have removed that
and integrated it in the main patch.


With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com

Commits

  1. Improve code comments in b0eaa4c51b.

  2. During pg_upgrade, conditionally skip transfer of FSMs.

  3. Add more tests for FSM.

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

  5. Make FSM test portable.

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

  7. Move page initialization from RelationAddExtraBlocks() to use, take 2.

  8. Avoid creation of the free space map for small heap relations.

  9. In bootstrap mode, don't allow the creation of files if they don't already