Thread: How best to work around the issue - regex string cannot contain brackets
One would consider the following would work, but it did not because the brackets.
select regexp_matches('Department for Transport (Parking)', 'Department for Transport (Parking)', 'g')
Can anyone enlighten me?
Regards,
David
Re: How best to work around the issue - regex string cannot contain brackets
From
Christophe Pettus
Date:
> On Feb 3, 2022, at 08:53, Shaozhong SHI <shishaozhong@gmail.com> wrote:
>
> One would consider the following would work, but it did not because the brackets.
> select regexp_matches('Department for Transport (Parking)', 'Department for Transport (Parking)', 'g')
>
> Can anyone enlighten me?
You escape the ()s with a backslash:
xof=# select regexp_matches('Department for Transport (Parking)', 'Department for Transport \(Parking\)', 'g');
regexp_matches
----------------------------------------
{"Department for Transport (Parking)"}
(1 row)
Re: How best to work around the issue - regex string cannot contain brackets
From
"David G. Johnston"
Date:
On Thu, Feb 3, 2022 at 9:58 AM Christophe Pettus <xof@thebuild.com> wrote:
> On Feb 3, 2022, at 08:53, Shaozhong SHI <shishaozhong@gmail.com> wrote:
>
> One would consider the following would work, but it did not because the brackets.
> select regexp_matches('Department for Transport (Parking)', 'Department for Transport (Parking)', 'g')
>
> Can anyone enlighten me?
Have you tried reading a book or some tutorials on RegExes? I'll admit our documentation is probably not the best resource out there to actually learn the language.
You escape the ()s with a backslash:
More generally this behavior this documented as "\k"
David J.
Re: How best to work around the issue - regex string cannot contain brackets
From
hubert depesz lubaczewski
Date:
On Thu, Feb 03, 2022 at 04:53:18PM +0000, Shaozhong SHI wrote:
> One would consider the following would work, but it did not because the
> brackets.
> select regexp_matches('Department for Transport (Parking)', 'Department for
> Transport (Parking)', 'g')
> Can anyone enlighten me?
Perhaps you don't want regexp matching, but simple equality or
substring match?
depesz
Re: How best to work around the issue - regex string cannot contain brackets
From
Shaozhong SHI
Date:
It appears that the following regex work differently.
Why \d and [\d] are different?
[A-PR-UWYZ]\d{1,2} and [A-PR-UWYZ][\d]{1,2}
Regards,
David
On Thu, 3 Feb 2022 at 17:04, David G. Johnston <david.g.johnston@gmail.com> wrote:
On Thu, Feb 3, 2022 at 9:58 AM Christophe Pettus <xof@thebuild.com> wrote:
> On Feb 3, 2022, at 08:53, Shaozhong SHI <shishaozhong@gmail.com> wrote:
>
> One would consider the following would work, but it did not because the brackets.
> select regexp_matches('Department for Transport (Parking)', 'Department for Transport (Parking)', 'g')
>
> Can anyone enlighten me?Have you tried reading a book or some tutorials on RegExes? I'll admit our documentation is probably not the best resource out there to actually learn the language.
You escape the ()s with a backslash:More generally this behavior this documented as "\k"David J.
Re: How best to work around the issue - regex string cannot contain brackets
From
Steve Midgley
Date:
On Fri, Feb 4, 2022 at 6:01 AM Shaozhong SHI <shishaozhong@gmail.com> wrote:
It appears that the following regex work differently.Why \d and [\d] are different?[A-PR-UWYZ]\d{1,2} and [A-PR-UWYZ][\d]{1,2}
This is getting into regex stuff, where maybe stackoverflow is a better resource? But when you put characters into brackets, you are telling regex to search for each character represented in the bracket. So [\d] is looking for any single character that is either a \ or a d character. Outside of brackets, regex evaluates \d as any digit. For US English charset [0-9] is equivalent to \d I believe.
Re: How best to work around the issue - regex string cannot contain brackets
From
"David G. Johnston"
Date:
On Fri, Feb 4, 2022 at 10:14 AM Steve Midgley <science@misuse.org> wrote:
On Fri, Feb 4, 2022 at 6:01 AM Shaozhong SHI <shishaozhong@gmail.com> wrote:It appears that the following regex work differently.Why \d and [\d] are different?[A-PR-UWYZ]\d{1,2} and [A-PR-UWYZ][\d]{1,2}
Show your work!
But when you put characters into brackets, you are telling regex to search for each character represented in the bracket. So [\d] is looking for any single character that is either a \ or a d character. Outside of brackets, regex evaluates \d as any digit.
This is simply wrong. Test it.
David J.
Re: How best to work around the issue - regex string cannot contain brackets
From
Steve Midgley
Date:
On Fri, Feb 4, 2022 at 9:24 AM David G. Johnston <david.g.johnston@gmail.com> wrote:
On Fri, Feb 4, 2022 at 10:14 AM Steve Midgley <science@misuse.org> wrote:On Fri, Feb 4, 2022 at 6:01 AM Shaozhong SHI <shishaozhong@gmail.com> wrote:It appears that the following regex work differently.Why \d and [\d] are different?[A-PR-UWYZ]\d{1,2} and [A-PR-UWYZ][\d]{1,2}Show your work!But when you put characters into brackets, you are telling regex to search for each character represented in the bracket. So [\d] is looking for any single character that is either a \ or a d character. Outside of brackets, regex evaluates \d as any digit.
Apologies - I was relying on stackoverflow and my prior experiences with regex engines that don't honor shorthand characters inside brackets. I should have tested postgres latest before responding. Thanks for the correction. (https://stackoverflow.com/questions/46020936/perl-like-shorthand-character-class-not-working-inside-bracket-expression)