Horton

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

Thomas Munro <thomas.munro@enterprisedb.com>

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From: Thomas Munro <thomas.munro@enterprisedb.com>
To: John Naylor <jcnaylor@gmail.com>
Cc: Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2018-10-05T20:42:26Z
Lists: pgsql-hackers 
On Sat, Oct 6, 2018 at 7:47 AM John Naylor <jcnaylor@gmail.com> wrote:
> A while back, Robert Haas noticed that the space taken up by very
> small tables is dominated by the FSM [1]. Tom suggested that we could
> prevent creation of the FSM until the heap has reached a certain
> threshold size [2]. Attached is a WIP patch to implement that. I've
> also attached a SQL script to demonstrate the change in behavior for
> various scenarios.

Hi John,

You'll need to tweak the test in contrib/pageinspect/sql/page.sql,
because it's currently asserting that there is an FSM on a small table
so make check-world fails.

-- 
Thomas Munro
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