Horton

Re: [HACKERS] Custom compression methods

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Dilip Kumar <dilipbalaut@gmail.com>, 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: 2021-03-19T20:38:03Z
Lists: pgsql-hackers 
On Fri, Mar 19, 2021 at 4:20 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Nope ... crake's displeased with your assumption that it's OK to
> clutter dumps with COMPRESSION clauses.  As am I: that is going to
> be utterly fatal for cross-version transportation of dumps.

Yes, and prion's got this concerning diff:

  Column |  Type   | Collation | Nullable | Default | Storage |
Compression | Stats target | Description
 --------+---------+-----------+----------+---------+---------+-------------+--------------+-------------
- f1     | integer |           |          |         | plain   |
     |              |
+ f1     | integer |           |          |         | plain   | pglz
     |              |

Since the column is not a varlena, it shouldn't have a compression
method configured, yet on that machine it does, possibly because that
machine uses -DRELCACHE_FORCE_RELEASE -DCATCACHE_FORCE_RELEASE.

Regarding your point, that does look like clutter. We don't annotate
the dump with a storage clause unless it's non-default, so probably we
should do the same thing here. I think I gave Dilip bad advice here...

-- 
Robert Haas
EDB: 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.