Re: Suggest using boolean index with (bflag is true) condition for the query with (bflag = true) clause

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
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