Re: Mixing greediness in regexp_matches

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Daniel Verite" <daniel(at)manitou-mail(dot)org>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Mixing greediness in regexp_matches
Date: 2019-12-23 15:26:15
Message-ID: 29225.1577114775@sss.pgh.pa.us
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"Daniel Verite" <daniel(at)manitou-mail(dot)org> writes:
>> The basic idea is to iterate on the rows produced by
>> regexp_matches(string, '(.*?)(foo|bar|foobar)', 'g')
>> to break down the string into pairs of (non-matching segment,
>> matching segment) so that a final result can be assembled
>> from that (setting aside the last non-matching segment, that
>> can be retrieved in a final step).

BTW, just to think outside the box a bit, I wonder whether you
couldn't build this out of regexp_split_to_array:

regression=# select regexp_split_to_array('junkfoolbarfoolishfoobarmore', 'foo|bar|foobar');
regexp_split_to_array
-----------------------
{junk,l,"",lish,more}
(1 row)

The idea would be to iterate over the array elements, tracking the
corresponding position in the source string, and re-discovering at
each break which of the original alternatives must've matched.

It's sort of annoying that we don't have a simple "regexp_location"
function that would give you back the starting position of the
first match.

regards, tom lane

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