Horton

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

John Naylor <jcnaylor@gmail.com>

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From: John Naylor <jcnaylor@gmail.com>
To: pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2018-10-14T16:29:28Z
Lists: pgsql-hackers

Attachments

> On 10/13/18, Amit Kapila <amit.kapila16@gmail.com> wrote:
>> I think you have found a good way to avoid creating FSM, but can't we
>> use some simpler technique like if the FSM fork for a relation doesn't
>> exist, then check the heapblk number for which we try to update the
>> FSM and if it is lesser than HEAP_FSM_EXTENSION_THRESHOLD, then avoid
>> creating the FSM.

>> I think it would be better if we can find a common way to avoid
>> creating FSM both during DO and REDO time.  It might be possible if
>> somethin like what I have said above is feasible.

I've attached v4, which implements the REDO case, and as closely as
possible to the DO case. I've created a new function to guard against
creation of the FSM, which is called by  RecordPageWithFreeSpace() and
RecordAndGetPageWithFreeSpace(). Since XLogRecordPageWithFreeSpace()
takes a relfilenode and not a relation, I had to reimplement that
separately, but the logic is basically the same. It works under
streaming replication.

I've also attached a couple SQL scripts which, when the aforementioned
DEBUG1 calls are enabled, show what the heap insert code is doing for
different scenarios. Make check-world passes.

-John Naylor

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