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: Justin Pryzby <pryzby@telsasoft.com>, Jaime Casanova <jcasanov@systemguards.com.ec>, Andres Freund <andres@anarazel.de>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, David Steele <david@pgmasters.net>, Ildus Kurbangaliev <i.kurbangaliev@gmail.com>, Dmitry Dolgov <9erthalion6@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2021-03-25T09:44:36Z
Lists: pgsql-hackers

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On Wed, Mar 24, 2021 at 10:57 PM Robert Haas <robertmhaas@gmail.com> wrote:
>
> On Wed, Mar 24, 2021 at 12:14 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
> > Actually, we are already doing this, I mean ALTER TABLE .. ALTER
> > COLUMN .. SET COMPRESSION is already updating the compression method
> > of the index attribute.  So 0003 doesn't make sense, sorry for the
> > noise.  However, 0001 and 0002 are still valid, or do you think that
> > we don't want 0001 also?  If we don't need 0001 also then we need to
> > update the test output for 0002 slightly.
>
> It seems to me that 0002 is still not right. We can't fix the
> attcompression to whatever the default is at the time the index is
> created, because the default can be changed later, and there's no way
> to fix index afterward. I mean, it would be fine to do it that way if
> we were going to go with the other model, where the index state is
> separate from the table state, either can be changed independently,
> and it all gets dumped and restored. But, as it is, I think we should
> be deciding how to compress new values for an expression column based
> on the default_toast_compression setting at the time of compression,
> not the time of index creation.
>

Okay got it.  Fixed as suggested.

-- 
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.