Horton

Re: [HACKERS] Custom compression methods

Tomas Vondra <tomas.vondra@2ndquadrant.com>

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From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
To: Евгений Шишкин <itparanoia@gmail.com>
Cc: Ildus Kurbangaliev <i.kurbangaliev@postgrespro.ru>, Andres Freund <andres@anarazel.de>, Robert Haas <robertmhaas@gmail.com>, Oleg Bartunov <obartunov@gmail.com>, Craig Ringer <craig@2ndquadrant.com>, Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2017-11-20T16:31:45Z
Lists: pgsql-hackers 

On 11/20/2017 04:43 PM, Евгений Шишкин wrote:
> 
> 
>> On Nov 20, 2017, at 18:29, Tomas Vondra <tomas.vondra@2ndquadrant.com> wrote:
>>
>>>
>>> What about instead of dropping column we leave data uncompressed?
>>>
>>
>> That requires you to go through the data and rewrite the whole table.
>> And I'm not aware of a DROP command doing that, instead they just drop
>> the dependent objects (e.g. DROP TYPE, ...). So per PLOS the DROP
>> COMPRESSION METHOD command should do that too.
> 
> Well, there is no much you can do with DROP TYPE. But i'd argue that compression
> is different. We do not drop data in case of DROP STATISTICS or DROP INDEX.
> 

But those DROP commands do not 'invalidate' data in the heap, so there's
no reason to drop the columns.

> At least there should be a way to easily alter compression method then.
> 

+1


regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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.