Thread: order of (escaped) characters in regex range

On 13 December 2011 14:04, InterRob <rob.marjot@gmail.com> wrote:

Dear List,

I found this interesting:

SELECT regexp_matches('123-A' , E'(3[A-Z\- ])');
ERROR:  invalid regular expression: invalid character range

whereas:
SELECT regexp_matches('123-A' , E'(3[\- A-Z])');
 regexp_matches
----------------
 {3-}
(1 row)

Notice the order of (escaped) characters and ranges in the last bit of the expression.

Am I missing some key concept of the regular expression?

Regards,
Rob

Hi Rob,

try '\\-' instead of '\-'

and it works :)

regards

On Tue, Dec 13, 2011 at 02:51:15PM +0100, InterRob wrote:
> Thanks guys, i see what you mean.
>
> I do intend to use the PG escaping, in order to avoid that annoying
> warning... Hence, my expression should indeed be:
> SELECT regexp_matches('123-A' , E'(3[A-Z\\-\\(\\) ])');
>
> In the above expression i added the parentheses as I whish to match these
> as well :))

instead of putting that much quoting just do:
SELECT regexp_matches('123-A' , '(3[A-Z() -])');
 ( and ) don't need to be quoted, and if you'll move - at the beginning
 or end (i prefer end) of range, it doesn't need to be quoted either.

Best regards,

depesz

--
The best thing about modern society is how easy it is to avoid contact with it.
                                                             http://depesz.com/

On Tue, Dec 13, 2011 at 7:51 AM, InterRob <rob.marjot@gmail.com> wrote:
> Thanks guys, i see what you mean.
>
> I do intend to use the PG escaping, in order to avoid that annoying
> warning... Hence, my expression should indeed be:
> SELECT regexp_matches('123-A' , E'(3[A-Z\\-\\(\\) ])');
>
> In the above expression i added the parentheses as I whish to match these as
> well :))

I advise dollar quoting when writing complicated regular expressions:

E'(3[A-Z\\-\\(\\) ])'
becomes
$$(3[A-Z\-\(\) ])$$

merlin

-----Original Message-----
From: pgsql-general-owner@postgresql.org
[mailto:pgsql-general-owner@postgresql.org] On Behalf Of Merlin Moncure
Sent: Tuesday, December 13, 2011 11:39 AM
To: rob@marjot-multisoft.com
Cc: David Johnston; Szymon Guz; pgsql-general
Subject: Re: [GENERAL] order of (escaped) characters in regex range

On Tue, Dec 13, 2011 at 7:51 AM, InterRob <rob.marjot@gmail.com> wrote:
> Thanks guys, i see what you mean.
>
> I do intend to use the PG escaping, in order to avoid that annoying
> warning... Hence, my expression should indeed be:
> SELECT regexp_matches('123-A' , E'(3[A-Z\\-\\(\\) ])');
>
> In the above expression i added the parentheses as I whish to match
> these as well :))

I advise dollar quoting when writing complicated regular expressions:

E'(3[A-Z\\-\\(\\) ])'
becomes
$$(3[A-Z\-\(\) ])$$

merlin

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---------------------------------------------------------------

Aside from backward compatibility, and the various warnings, is there any
reason to prefer dollar-quoting over a non-SQL-escaped string literal (i.e.,
'3[A-Z\-\(\) ]'   ) ?

David J.

On Tue, Dec 13, 2011 at 10:53 AM, David Johnston <polobo@yahoo.com> wrote:
> Aside from backward compatibility, and the various warnings, is there any
> reason to prefer dollar-quoting over a non-SQL-escaped string literal (i.e.,
> '3[A-Z\-\(\) ]'   ) ?

yeah -- because sooner or later you have to stick a single quote in
there (of course, you can double the ', but I personally think that's
awful).

merlin