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From: jian he <jian.universality@gmail.com>
Date: Wed, 22 Jan 2025 14:21:05 +0800
Message-ID: <CACJufxHTBkymh06D4mGKNe1YfRNFN+gFBybmygWk=PtMqu00LQ@mail.gmail.com>
Subject: add function argument name to substring and substr
To: PostgreSQL-development <pgsql-hackers@postgresql.org>
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Archived-At: <https://www.postgresql.org/message-id/CACJufxHTBkymh06D4mGKNe1YfRNFN%2BgFBybmygWk%3DPtMqu00LQ%40mail.gmail.com>
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hi.

attached patch add function argument name to function substring and substr
you can see the visual changes.
mater behavior:

\df substring
                             List of functions
   Schema   |   Name    | Result data type |   Argument data types   | Type
------------+-----------+------------------+-------------------------+------
 pg_catalog | substring | bit              | bit, integer            | func
 pg_catalog | substring | bit              | bit, integer, integer   | func
 pg_catalog | substring | bytea         | bytea, integer          | func
 pg_catalog | substring | bytea         | bytea, integer, integer | func
 pg_catalog | substring | text             | text, integer           | func
 pg_catalog | substring | text             | text, integer, integer  | func
 pg_catalog | substring | text             | text, text              | func
 pg_catalog | substring | text             | text, text, text        | func

with patch
                                          List of functions
   Schema   |   Name    | Result data type |               Argument
data types                | Type
------------+-----------+------------------+--------------------------------------------------+------
 pg_catalog | substring | bit              | bits bit, start integer
                       | func
 pg_catalog | substring | bit              | bits bit, start integer,
count integer           | func
 pg_catalog | substring | bytea         | bytes bytea, start integer
                    | func
 pg_catalog | substring | bytea         | bytes bytea, start integer,
count integer        | func
 pg_catalog | substring | text             | string text, pattern text
                       | func
 pg_catalog | substring | text             | string text, pattern
text, escape_character text | func
 pg_catalog | substring | text             | string text, start
integer                       | func
 pg_catalog | substring | text             | string text, start
integer, count integer        | func

I did the same change to the function substr.
since 9.7.2. SIMILAR TO Regular Expressions we use
substring(string, pattern, escape-character)
so i refactor the substring function argument name to
substring(string text, pattern text, escape_character text).

we can make it as ``substring(string text, pattern text, escape text).``
then in 9.7.2, we need to change the substring synopsis section.


one thing I am not sure is about
9.4. String Functions and Operators
Table 9.9. SQL String Functions and Operators.
Do we need entries for substring related functions?

current signature
substring ( string text [ FROM start integer ] [ FOR count integer ] )
is kind of different from
substring(string text, start integer, count integer).
since the previous one can allow keywords "FROM", "FOR", the latter one won't.