Horton

Re: [HACKERS] Custom compression methods

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Justin Pryzby <pryzby@telsasoft.com>
Cc: David Steele <david@pgmasters.net>, 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>, Ildus Kurbangaliev <i.kurbangaliev@gmail.com>, Dmitry Dolgov <9erthalion6@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Tom Lane <tgl@sss.pgh.pa.us>
Date: 2021-04-08T20:07:53Z
Lists: pgsql-hackers 
On Thu, Apr 8, 2021 at 3:38 PM Justin Pryzby <pryzby@telsasoft.com> wrote:
> It looks like this should not remove the word "data" ?

Oh, yes, right.

>  The compression technique used for either in-line or out-of-line compressed
> -data is a fairly simple and very fast member
> -of the LZ family of compression techniques.  See
> -<filename>src/common/pg_lzcompress.c</filename> for the details.
> +can be selected using the <literal>COMPRESSION</literal> option on a per-column
> +basis when creating a table. The default for columns with no explicit setting
> +is taken from the value of <xref linkend="guc-default-toast-compression" />.
>
> I thought this patch would need to update parts about borrowing 2 spare bits,
> but maybe that's the wrong header..before.

We're not borrowing any more bits from the places where we were
borrowing 2 bits before. We are borrowing 2 bits from places that
don't seem to be discussed in detail here, where no bits were borrowed
before.

-- 
Robert Haas
EDB: 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.