Horton

Re: [HACKERS] Custom compression methods

Dilip Kumar <dilipbalaut@gmail.com>

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From: Dilip Kumar <dilipbalaut@gmail.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, Justin Pryzby <pryzby@telsasoft.com>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, Alexander Korotkov <a.korotkov@postgrespro.ru>, David Steele <david@pgmasters.net>, Ildus Kurbangaliev <i.kurbangaliev@gmail.com>, Dmitry Dolgov <9erthalion6@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2021-03-16T15:21:01Z
Lists: pgsql-hackers 
On Tue, Mar 16, 2021 at 7:57 PM Robert Haas <robertmhaas@gmail.com> wrote:
>

> That behavior feels unacceptable to me from a user expectations point
> of view. I think there's an argument that if I update a tuple that
> contains a compressed datum, and I don't update that particular
> column, I think it would be OK to not recompress the column. But, if I
> insert data into a table, I as a user would expect that the
> compression settings for that column are going to be respected.
> Deciding that's optional because we don't have a good way of making it
> fast seems like a major cop-out, at least to me. I think from a user
> perspective you don't expect INSERT INTO .. SELECT FROM to create a
> different final state than a dump and reload, and that if we deviate
> from that people are gonna be unhappy. I could be wrong; maybe it's
> only me who would be unhappy.

If that is only the argument then it's possible today as well.  I mean
you can INSERT INTO .. SELECT FROM where source attribute as
compressed data but the target attribute as external storage then also
we will move the compressed data as it is to the target table.

-- 
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com

Commits

  1. docs: Update TOAST storage docs for configurable compression.

  2. Further tweaking of pg_dump's handling of default_toast_compression.

  3. Fix interaction of TOAST compression with expression indexes.

  4. Tidy up more loose ends related to configurable TOAST compression.

  5. Short-circuit slice requests that are for more than the object's size.

  6. Mostly-cosmetic adjustments of TOAST-related macros.

  7. Remove useless configure probe for <lz4/lz4.h>.

  8. Error on invalid TOAST compression in CREATE or ALTER TABLE.

  9. docs: Fix omissions related to configurable TOAST compression.

  10. More code cleanup for configurable TOAST compression.

  11. Bring configure support for LZ4 up to snuff.

  12. Make compression.sql regression test independent of default.

  13. Use valid compression method in brin_form_tuple

  14. Fix up pg_dump's handling of per-attribute compression options.

  15. Allow configurable LZ4 TOAST compression.

  16. Fix inconsistencies in the code

  17. Mostly-cosmetic improvements in memory chunk header alignment coding.

  18. Allow numeric to use a more compact, 2-byte header in many cases.