Horton

Re: Index-only scans vs. partially-retrievable indexes

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andrey Borodin <x4mmm@yandex-team.ru>
Cc: pgsql-hackers@lists.postgresql.org
Date: 2022-01-03T14:57:14Z
Lists: pgsql-hackers 
Andrey Borodin <x4mmm@yandex-team.ru> writes:
> I've tried to toy with the patch and remembered one related caveat.
> If we have index for both returnable and nonreturnable attributes, IOS will not be choosen:

> postgres=# create index on t using gist(a gist_trgm_ops) include (a);
> postgres=# explain select * from t where a like 'z';
>                              QUERY PLAN                              
> ---------------------------------------------------------------------
>  Index Scan using t_a_a1_idx on t  (cost=0.12..8.14 rows=1 width=32)
>    Index Cond: (a ~~ 'z'::text)
> (2 rows)

This case is improved by 0002, no?

			regards, tom lane

Commits

  1. Handle mixed returnable and non-returnable columns better in IOS.

  2. Fix index-only scan plans, take 2.