Re: Suggest using boolean index with (bflag is true) condition for the query with (bflag = true) clause - Mailing list pgsql-general

From Laurenz Albe
Subject Re: Suggest using boolean index with (bflag is true) condition for the query with (bflag = true) clause
Date
Msg-id dcceae342f9ee16e84acf2f215dec73d0757b6a2.camel@cybertec.at
Whole thread Raw
In response to Suggest using boolean index with (bflag is true) condition for the query with (bflag = true) clause  (Евгений Плискин <eugene.pliskin@gmail.com>)
Responses Re: Suggest using boolean index with (bflag is true) condition for the query with (bflag = true) clause
List pgsql-general
On Sun, 2022-09-18 at 18:24 +0300, Евгений Плискин wrote:
> This is not a bug report but rather a suggestion.
> 
> Suppose database contains an index on a boolean column like this:
>       create table1(id int, amount float, best_record boolean);
>       create index index1 on table1(best_record) where best_record is true;
> 
> And suppose we issue a query like this:
>       select * from table1 where best_record = true;
> 
> The planner does not try to use an index for this query because an index condition (bflag is true) does not literally
matchthe query (bflag = true). 
 
> But is that reasonable?
> The index does not cover records where "best_record" is FALSE or NULL.
> And similarly the query is not interested in any records where "best_record" is FALSE or NULL.
> So why not use this index for this query?

Because the conditions are different:

SELECT NULL = TRUE, NULL IS TRUE;
 ?column? │ ?column? 
══════════╪══════════
          │ f
(1 row)

The first result is NULL.

Yours,
Laurenz Albe
-- 
Cybertec | https://www.cybertec-postgresql.com



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