Horton

Re: [HACKERS] Custom compression methods

Ildus Kurbangaliev <i.kurbangaliev@postgrespro.ru>

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From: Ildus Kurbangaliev <i.kurbangaliev@postgrespro.ru>
To: Ildar Musin <i.musin@postgrespro.ru>
Cc: Robert Haas <robertmhaas@gmail.com>, Alexander Korotkov <a.korotkov@postgrespro.ru>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, Евгений Шишкин <itparanoia@gmail.com>, Andres Freund <andres@anarazel.de>, Oleg Bartunov <obartunov@gmail.com>, Craig Ringer <craig@2ndquadrant.com>, Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>, Chapman Flack <chap@anastigmatix.net>
Date: 2018-01-23T13:04:54Z
Lists: pgsql-hackers

Attachments

On Mon, 22 Jan 2018 23:26:31 +0300
Ildar Musin <i.musin@postgrespro.ru> wrote:

Thanks for review! Attached new version of the patch. Fixed few bugs,
added more documentation and rebased to current master.

> You need to rebase to the latest master, there are some conflicts.
> I've applied it to the three days old master to try it.

Done.

> 
> As I can see the documentation is not yet complete. For example, there
> is no section for ALTER COLUMN ... SET COMPRESSION in ddl.sgml; and
> section "Compression Access Method Functions" in compression-am.sgml
> hasn't been finished.

Not sure about ddl.sgml, it contains more common things, but since
postgres contains only pglz by default there is not much to show.

> 
> I've implemented an extension [1] to understand the way developer
> would go to work with new infrastructure. And for me it seems clear.
> (Except that it took me some effort to wrap my mind around varlena
> macros but it is probably a different topic).
> 
> I noticed that you haven't cover 'cmdrop' in the regression tests and
> I saw the previous discussion about it. Have you considered using
> event triggers to handle the drop of column compression instead of
> 'cmdrop' function? This way you would kill two birds with one stone:
> it still provides sufficient infrastructure to catch those events
> (and it something postgres already has for different kinds of ddl
> commands) and it would be easier to test.

I have added support for event triggers for ALTER SET COMPRESSION in
current version. Event trigger on ALTER can be used to replace cmdrop
function but it will be far from trivial. There is not easy way to
understand that's attribute compression is really dropping in the
command.

-- 
---
Ildus Kurbangaliev
Postgres Professional: http://www.postgrespro.com
Russian Postgres Company

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.