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: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: John Naylor <john.naylor@2ndquadrant.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2019-02-22T02:59:27Z
Lists: pgsql-hackers

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On Fri, Feb 22, 2019 at 1:57 AM Alvaro Herrera <alvherre@2ndquadrant.com> wrote:
>
> I think this test is going to break on nonstandard block sizes.  While
> we don't promise that all tests work on such installs (particularly
> planner ones),
>

The reason for not pushing much on making the test pass for
nonstandard block sizes is that when I tried existing tests, there
were already some failures.  For example, see the failures in the
attached regression diff files (for block_size as 16K and 32K
respectively).  I saw those failures during the previous
investigation, the situation on HEAD might or might not be exactly the
same.  Whereas I see the value in trying to make sure that tests pass
for nonstandard block sizes, but that doesn't seem to be followed for
all the tests.

> it seems fairly easy to cope with this one -- just use a
> record size expressed as a fraction of current_setting('block_size').
> So instead of "1024" you'd write current_setting('block_size') / 8.
> And then display the relation size in terms of pages, not bytes, so
> divide pg_relation_size by block size.
>

The idea sounds good.  John, would you like to give it a try?

-- 
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