agora inbox for pgsql-docs@postgresql.org
help / color / mirror / Atom feedFrom: Tom Lane <tgl@sss.pgh.pa.us>
To: jian he <jian.universality@gmail.com>
Cc: pgsql-docs@lists.postgresql.org
Subject: Re: substring synopsis section, third argument is optional doc didn't show that
Date: Tue, 21 Jan 2025 11:53:24 -0500
Message-ID: <3354664.1737478404@sss.pgh.pa.us> (raw)
In-Reply-To: <CACJufxG0npso=EwpMHeqG1tFhHayo9o51cTfjP9imj3WNvVBvA@mail.gmail.com>
References: <CACJufxG0npso=EwpMHeqG1tFhHayo9o51cTfjP9imj3WNvVBvA@mail.gmail.com>
jian he <jian.universality@gmail.com> writes:
> https://www.postgresql.org/docs/current/functions-matching.html#FUNCTIONS-SIMILARTO-REGEXP
> """
> or as a plain three-argument function:
> substring(string, pattern, escape-character)
> """
> but here "escape-character" is optional.
> substring(string, pattern [,escape-character])
> would be more accurate.
No, the text is correct as written. substring(text, text) is a
completely different function that implements POSIX regular
expressions, not SQL regular expressions. It's described in
the next section (9.7.3). For example,
regression=# select substring('foobar', 'o.b');
substring
-----------
oob
(1 row)
regression=# select substring('foobar', 'o.b', '');
substring
-----------
(1 row)
because '.' is a metacharacter in POSIX but not SQL regexps.
regards, tom lane
view thread (5+ messages) latest in thread
Message-ID: <3354664.1737478404@sss.pgh.pa.us>
Permalink: ../3354664.1737478404@sss.pgh.pa.us/
Also on: postgresql.org/message-id/3354664.1737478404@sss.pgh.pa.us
reply
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-docs@postgresql.org
Cc: tgl@sss.pgh.pa.us, jian.universality@gmail.com, pgsql-docs@lists.postgresql.org
Subject: Re: substring synopsis section, third argument is optional doc didn't show that
In-Reply-To: <3354664.1737478404@sss.pgh.pa.us>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox