Horton

Re: [HACKERS] Custom compression methods

Justin Pryzby <pryzby@telsasoft.com>

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From: Justin Pryzby <pryzby@telsasoft.com>
To: Tomas Vondra <tomas.vondra@enterprisedb.com>
Cc: Dilip Kumar <dilipbalaut@gmail.com>, Robert Haas <robertmhaas@gmail.com>, Andres Freund <andres@anarazel.de>, 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>, pgsql-hackers@lists.postgresql.org
Date: 2021-03-20T15:21:46Z
Lists: pgsql-hackers 
On Sat, Mar 20, 2021 at 04:13:47PM +0100, Tomas Vondra wrote:
> +++ b/src/backend/access/brin/brin_tuple.c
> @@ -213,10 +213,20 @@ brin_form_tuple(BrinDesc *brdesc, BlockNumber blkno, BrinMemTuple *tuple,
>  				(atttype->typstorage == TYPSTORAGE_EXTENDED ||
>  				 atttype->typstorage == TYPSTORAGE_MAIN))
>  			{
> +				Datum	cvalue;
> +				char	compression = GetDefaultToastCompression();
>  				Form_pg_attribute att = TupleDescAttr(brdesc->bd_tupdesc,
>  													  keyno);
> -				Datum		cvalue = toast_compress_datum(value,
> -														  att->attcompression);
> +
> +				/*
> +				 * If the BRIN summary and indexed attribute use the same data
> +				 * type, we can the same compression method. Otherwise we have

can *use ?

> +				 * to use the default method.
> +				 */
> +				if (att->atttypid == atttype->type_id)
> +					compression = att->attcompression;

It would be more obvious to me if this said here: 
| else: compression = GetDefaultToastCompression

-- 
Justin

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.