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: 2019-01-30T13:11:01Z
Lists: pgsql-hackers 
On Wed, Jan 30, 2019 at 3:26 PM John Naylor <john.naylor@2ndquadrant.com> wrote:
>
> On Wed, Jan 30, 2019 at 4:33 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
> > There are two more failures which we need to something about.
> > 1. Make fsm.sql independent of vacuum without much losing on coverage
> > of newly added code.  John, I guess you have an idea, see if you can
> > take care of it, otherwise, I will see what I can do for it.
>
> I've attached a patch that applies on top of v19 that uses Andrew
> Gierth's idea to use fillfactor to control free space. I've also
> removed tests that relied on truncation and weren't very useful to
> begin with.
>

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?

-- 
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