Horton

Re: [HACKERS] Custom compression methods

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Cc: Ildus Kurbangaliev <i.kurbangaliev@postgrespro.ru>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2017-12-17T03:32:09Z
Lists: pgsql-hackers 
On Thu, Dec 14, 2017 at 12:23 PM, Tomas Vondra
<tomas.vondra@2ndquadrant.com> wrote:
> Can you give an example of such algorithm? Because I haven't seen such
> example, and I find arguments based on hypothetical compression methods
> somewhat suspicious.
>
> FWIW I'm not against considering such compression methods, but OTOH it
> may not be such a great primary use case to drive the overall design.

Well it isn't, really.  I am honestly not sure what we're arguing
about at this point.  I think you've agreed that (1) opening avenues
for extensibility is useful, (2) substitution a general-purpose
compression algorithm could be useful, and (3) having datatype
compression that is enabled through TOAST rather than built into the
datatype might sometimes be desirable.  That's more than adequate
justification for this proposal, whether half-general compression
methods exist or not.  I am prepared to concede that there may be no
useful examples of such a thing.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL 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.