Re: Regular expression question with Postgres

From: David G Johnston <david(dot)g(dot)johnston(at)gmail(dot)com>
To: pgsql-general(at)postgresql(dot)org
Subject: Re: Regular expression question with Postgres
Date: 2014-07-24 20:42:16
Message-ID: 1406234536911-5812778.post@n5.nabble.com
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Mike Christensen-2 wrote
> I'm curious why this query returns 0:
>
> SELECT 'AAA' ~ '^A{,4}$'
>
> Yet, this query returns 1:
>
> SELECT 'AAA' ~ '^A{0,4}$'
>
> Is this a bug with the regular expression engine?

Apparently since "{,#}" is not a valid regexp expression the engine simply
interprets it as a literal and says 'AAA' != 'A{,4}'

http://www.postgresql.org/docs/9.3/interactive/functions-matching.html#FUNCTIONS-POSIX-REGEXP

Table 9-13. Regular Expression Quantifiers

Note the all of the { } expressions have a lower bound (whether explicit or
implied).

David J.

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