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From: Jian He <[email protected]>
To: [email protected]
Subject: stxkind only explain two elements. left two unexplained.
Date: Wed, 6 Apr 2022 10:31:55 +0530
Message-ID: <CAMV54g1+xGwtFHTtnXOJW_Lc4+i1tfReBY_ZkRgkXQqM8wGXJA@mail.gmail.com> (raw)

PostgreSQL: Documentation: 10: 51.51. pg_statistic_ext
<https://www.postgresql.org/docs/10/catalog-pg-statistic-ext.html;

> stxkind : An array containing codes for the enabled statistics kinds;
> valid values are: d for n-distinct statistics, f for functional
> dependency statistics


select distinct stxkind from pg_statistic_ext ;
return:

 stxkind
> ---------
>  {d}
>  {m}
>  {f}
>  {e}
> (4 rows)


 I guess *e *for expression statistics. Since I create the following
statistics object.

create statistics flight_expr1 on(
    extract
    (month from scheduled_departure at time zone 'Asia/Kolkata')
    ) from flights;

select stxkind from pg_statistic_ext where stxname =  'flight_expr';

and it return *e.*
But I am not sure what does *m *mean?

It would be better to full explain all these four elements in the doc.

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