Re: Regexp named capture groups

2018-02-03 11:19 GMT+01:00 Joel Jacobson <joel(at)trustly(dot)com>:

> Hi hackers,
>
> Is anyone working on this feature[1] also for PostgreSQL's regex engine?
>
> I'm thinking it could work something like this:
>
> joel=# \df regexp_match
> List of functions
> Schema | Name | Result data type | Argument data types | Type
> ------------+--------------+------------------+-------------
> --------+--------
> pg_catalog | regexp_match | jsonb | text, text |
> normal
> pg_catalog | regexp_match | jsonb | text, text, text |
> normal
> (2 rows)
>
> joel=#* SELECT regexp_match_named(
> joel(#* '2018-12-31',
> joel(#* '(?<year>[0-9]{4})-(?<month>[0-9]{2})-(?<day>[0-9]{2})'
> joel(#* );
> regexp_match_named
> ----------------------------------------------
> {"day": "31", "year": "2018", "month": "12"}
> (1 row)
>
> I think this feature would be awesome, for the reasons mentioned in [1],
> quote:
>
> "Referring to capture groups via numbers has several disadvantages:
> 1. Finding the number of a capture group is a hassle: you have to
> count parentheses.
> 2. You need to see the regular expression if you want to understand
> what the groups are for.
> 3. If you change the order of the capture groups, you also have to
> change the matching code."
>
> [1] http://2ality.com/2017/05/regexp-named-capture-groups.html

looks like nice feature

Pavel

>
>
> Best regards,
>
> Joel Jacobson
>
>