Undocumented behaviour of \s in SIMILAR TO expression

On Thu, Dec 13, 2018 at 12:48:10PM +0000, PG Doc comments form wrote:

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/11/functions-matching.html
Description:

SELECT ' ' SIMILAR TO '[\s]';
returns true

SELECT ' ' SIMILAR TO '[\q]';
generates an error: [2201B]: ERROR: invalid regular expression: invalid
escape \ sequence

\s is not mentioned in the SIMILAR TO section
(https://www.postgresql.org/docs/current/functions-matching.html#FUNCTIONS-SIMILARTO-REGEXP).
If it’s officially supported (which would be useful for my current task), it
should be documented. Otherwise the server should generate an error like for
other invalid escapes.

Well in:

https://www.postgresql.org/docs/11/functions-matching.html

I see \s documented, but not \q:

Table 9.19. Regular Expression Class-shorthand Escapes
Escape Description
\d [[:digit:]]
\s [[:space:]]
\w [[:alnum:]_] (note underscore is included)
\D [^[:digit:]]
\S [^[:space:]]
\W [^[:alnum:]_] (note underscore is included)

Frankly, I can't even guess what you expect \q to do.

--
Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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