Horton

Re: [HACKERS] Custom compression methods

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Justin Pryzby <pryzby@telsasoft.com>, Andrew Dunstan <andrew@dunslane.net>, Dilip Kumar <dilipbalaut@gmail.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Andres Freund <andres@anarazel.de>, 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: 2021-03-30T14:30:32Z
Lists: pgsql-hackers 
Robert Haas <robertmhaas@gmail.com> writes:
> On Wed, Mar 24, 2021 at 2:15 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> But let's ignore the case of pg_upgrade and just consider a dump/restore.
>> I'd still say that unless you give --no-toast-compression then I would
>> expect the dump/restore to preserve the tables' old compression behavior.
>> Robert's argument that the pre-v14 database had no particular compression
>> behavior seems nonsensical to me.  We know exactly which compression
>> behavior it has.

> I said that it didn't have a state, not that it didn't have a
> behavior. That's not exactly the same thing. But I don't want to argue
> about it, either. It's a judgement call what's best here, and I don't
> pretend to have all the answers. If you're sure you've got it right
> ... great!

I've not heard any other comments about this, but I'm pretty sure that
preserving a table's old toast behavior is in line with what we'd normally
expect pg_dump to do --- especially in light of the fact that we did not
provide any --preserve-toast-compression switch to tell it to do so.
So I'm going to go change it.

			regards, tom lane

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.