Re: Move pg_attribute.attcompression to earlier in struct for reduced size?

From: Michael Paquier <michael(at)paquier(dot)xyz>
To: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, pgsql-hackers(at)postgresql(dot)org, Dilip Kumar <dilipbalaut(at)gmail(dot)com>
Subject: Re: Move pg_attribute.attcompression to earlier in struct for reduced size?
Date: 2021-05-27 00:13:30
Message-ID: YK7kKhV1fyWdAynz@paquier.xyz
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On Wed, May 26, 2021 at 07:44:03PM -0400, Alvaro Herrera wrote:
> On 2021-May-26, Tom Lane wrote:
>> Personally I won't touch 002_pg_dump.pl with a 10-foot pole, but if
>> somebody else wants to, have at it.
>
> Nod.

Yeah, having an extra test for partitioned tables would be a good
idea.

>> Hm, there's this in compression.sql:
>>
>> -- test LIKE INCLUDING COMPRESSION
>> CREATE TABLE cmdata2 (LIKE cmdata1 INCLUDING COMPRESSION);
>> \d+ cmdata2
>>
>> Or did you mean the case with a partitioned table specifically?
>
> Ah, I guess that's sufficient. (The INCLUDING clause cannot be used to
> create a partition, actually.)

+column_compression:
+ COMPRESSION ColId { $$ = $2; }
+ | COMPRESSION DEFAULT { $$ =
pstrdup("default"); }
Could it be possible to have some tests for COMPRESSION DEFAULT? It
seems to me that this should be documented as a supported keyword for
CREATE/ALTER TABLE.

--changing column storage should not impact the compression method
--but the data should not be compressed
ALTER TABLE cmdata2 ALTER COLUMN f1 TYPE varchar;
+ALTER TABLE cmdata2 ALTER COLUMN f1 SET COMPRESSION pglz;
This comment needs a refresh?
--
Michael

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