Re: [PATCH] pg_stat_toast

Am 20.12.2021 um 04:20 schrieb kuroda.hayato@fujitsu.com:
> Dear Gunnar,

Hi Kuroda-San!

>> postgres=# CREATE TABLE test (i int, lz4 text COMPRESSION lz4, std text);
>> postgres=# INSERT INTO test  SELECT
>> i,repeat(md5(i::text),100),repeat(md5(i::text),100) FROM
>> generate_series(0,100000) x(i);
>> postgres=# SELECT * FROM pg_stat_toast WHERE schemaname = 'public';
>> -[ RECORD 1 ]--------+----------
>> schemaname           | public
>> reloid               | 16829
>> attnum               | 2
>> relname              | test
>> attname              | lz4
>> externalizations     | 0
>> compressions         | 100001
>> compressionsuccesses | 100001
>> compressionsizesum   | 6299710
>> originalsizesum      | 320403204
>> -[ RECORD 2 ]--------+----------
>> schemaname           | public
>> reloid               | 16829
>> attnum               | 3
>> relname              | test
>> attname              | std
>> externalizations     | 0
>> compressions         | 100001
>> compressionsuccesses | 100001
>> compressionsizesum   | 8198819
>> originalsizesum      | 320403204
> 
> I'm not sure about TOAST, but currently compressions are configurable:
> https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=bbe0a81db69bd10bd166907c3701492a29aca294
> 
> How about adding a new attribute "method" to pg_stat_toast?
> ToastAttrInfo *attr->tai_compression represents how compress the data,
> so I think it's easy to add.
> Or, is it not needed because pg_attr has information?

That information could certainly be included in the view, grabbing the 
information from pg_attribute.attcompression. It probably should!

I guess the next step will be to include that view in the catalog 
anyway, so I'll do that next.

Thx for the feedback!
-- 
Gunnar "Nick" Bluth

Eimermacherweg 106
D-48159 Münster

Mobil +49 172 8853339
Email: gunnar.bluth@pro-open.de
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