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>, 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: 2021-03-09T07:34:10Z
Lists: pgsql-hackers 
On Tue, Mar 9, 2021 at 2:45 AM Robert Haas <robertmhaas@gmail.com> wrote:
>
> On Mon, Mar 8, 2021 at 3:59 PM Justin Pryzby <pryzby@telsasoft.com> wrote:
> > > It would be nice to have a way to force
> > > anything compressed with the old method to be re-compressed with the
> > > new method, but not having that doesn't preclude allowing the
> > > parameter to be changed.
> >
> > Doesn't vacuum full/cluster/dump+restore do that ?
>
> Well, dump and restore will do it, certainly, but I don't think VACUUM
> FULL or CLUSTER will. I haven't tested it, though, so maybe I'm wrong.

Yeah, vacuum full or cluster will not re-compress the data.  How about
providing syntax ALTER TABLE <tab-name> ALTER COLUMN <col_name> SET
COMPRESSION <com_name> REWRITE?  So if we have given a rewrite then we
will always rewrite the table and in an attempt to rewrite we will
re-compress the data.  If REWRITE is given and the compression method
is the same as the existing then also we can not skip the rewrite
because we don't know the history, the user might alter the
compression method multiple times without rewrite.

-- 
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.