Horton

Re: [HACKERS] Custom compression methods

Dilip Kumar <dilipbalaut@gmail.com>

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From: Dilip Kumar <dilipbalaut@gmail.com>
To: Justin Pryzby <pryzby@telsasoft.com>
Cc: Robert Haas <robertmhaas@gmail.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: 2021-03-07T12:34:41Z
Lists: pgsql-hackers 
On Sun, Mar 7, 2021 at 2:19 PM Justin Pryzby <pryzby@telsasoft.com> wrote:
>
> Earlier in this thread, I suggested to implement an option to pg_restore to
> avoid outputting compression, in order to allow restoring with a different
> compression (by using the default_toast_compression GUC).  Now, it seems like
> that's even more important, to allow restoring into binaries --without-lz4.
> (the pg_dump isn't in LZ4 format, it just needs to not say "COMPRESSION LZ4").

IMHO, we have an option with pg_dump that should be sufficient, no?
but I agree that having such an option with restore will give more
flexibility basically, by using the same dump we can restore to binary
--with-lz4 as well as without-lz4 if such option exists with restore
as well.  But it seems in pg_restore we process token by token so if
we want to implement such an option then I think we will have to parse
the complete string of CREATE TABLE command and remove the compression
option if it exists for any attribute. I am not sure whether providing
this option is worth the complexity?

> I think you're planning to allow the CREATE TABLE to succeed in any case, but
> it's not helpful if the DBA has to restore the schema, and then alter all the
> text columns to set PGLZ, and then restore the data and post-data.
>
> Also, I suggest to rename the pg_dump option:
> | --no-compression-methods     do not dump compression methods
>
> I have a patch to pg_dump to support alternate compression in the dump itself
> (in addition to zlib), so the name will be confusing.  I suggest
> --no-toast-compression, like the GUC.  And the same for pg_restore.

Ok.

--
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.