From: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
---|---|
To: | Adrien Nayrat <adrien(dot)nayrat(at)dalibo(dot)com> |
Cc: | pgsql-docs(at)postgresql(dot)org |
Subject: | Re: Text operators "~<=~ ~<~ ~>=~ ~>~" not documented |
Date: | 2018-02-08 15:32:50 |
Message-ID: | CAKFQuwZiuWg5QEk-tN+=Y8JS1cY-xFxe0xZKbMLBh1TM-fSh7w@mail.gmail.com |
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Lists: | pgsql-docs |
On Thu, Feb 8, 2018 at 6:26 AM, Adrien Nayrat <adrien(dot)nayrat(at)dalibo(dot)com>
wrote:
> Hello,
>
> While reading [1] I notice $subject operators lacks of explanation in
> documentation.
> [..]
>
>
> ~<~ less than
> ~>~ greater than
> ~<=~ less than or equal to
> ~>=~ greater than or equal to
>
> For all, it is a character-by-character comparison regardless of
> collation. We
> encounter them when we use text_pattern_ops for example :
>
> create index ON users ( location text_pattern_ops);
> explain select * from users where location like 'test%';
> QUERY PLAN
> ------------------------------------------------------------
> ------------------------
> Index Scan using users_location_idx1 on users (cost=0.43..2.46 rows=54
> width=201)
> Index Cond: ((location ~>=~ 'test'::text) AND (location ~<~
> 'tesu'::text))
> Filter: (location ~~ 'test%'::text)
> (3 lignes)
>
>
> Should we add them on this page?
> https://www.postgresql.org/docs/devel/static/functions-string.html
>
> Thanks!
>
>
> 1: https://www.postgresql.org/docs/current/static/spgist-
> builtin-opclasses.html
>
>
I'd be inclined to remove those four operators from the spgist page's table
and replace them with "LIKE". Then in the text below the table explain
that LIKE is implemented using a combination of those four operators.
If we do add them to the functions and operators chapter it should be in
the pattern matching section:
https://www.postgresql.org/docs/devel/static/functions-matching.html
9.7.1 LIKE needs a table containing [!]~~ and [!]~~* added anyway; tacking
these on as well and noting them as implementation functions (i.e., not
something a user would want to invoke directly typically) would be
appropriate.
David J.
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