Re: [Patch] Make block and file size for WAL and relations defined atcluster creation

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От Remi Colinet
Тема Re: [Patch] Make block and file size for WAL and relations defined atcluster creation
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Msg-id CADdR5nzYfVLo2AyZ+py7mBvivbu-ucGG00=TWkdcBoFXw80Jdg@mail.gmail.com
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Ответ на Re: [Patch] Make block and file size for WAL and relations defined atcluster creation  (Robert Haas <robertmhaas@gmail.com>)
Ответы Re: [Patch] Make block and file size for WAL and relations defined atcluster creation
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2018-01-03 22:04 GMT+01:00 Robert Haas <robertmhaas@gmail.com>:
On Wed, Jan 3, 2018 at 3:43 PM, Remi Colinet <remi.colinet@gmail.com> wrote:
> Justifications are:

I think this is all missing the point.  If varying the block size (or
whatever) is beneficial, then having it configurable at initdb is
clearly useful.  But, as Andres says, you haven't submitted any
evidence that this is the case.  You need to describe scenarios in
which (1) a non-default blocksize performs better and (2) there's no
reasonable way to obtain the same performance improvement without
changing the block size.

Block size does not boils down only to performance.

For instance, having a larger block size allows:
- to avoid toasting tuples. Rows with sizes larger that the default block size can justify larger block sizes.
- to reduce fragmentation in relations.

If changing the block size at initdb is useless, then why allowing developer to set such block size at compile time?
The patch only allows to shift the block size choice from compilation to run-time.

Regards
Remi


--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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