Re: writing new regexp functions

On Thu, 1 Feb 2007, David Fetter wrote:

> Yes, although it might have the same name, as in regex_match(pattern
> TEXT, string TEXT, return_pre_and_post BOOL).
>
> The data structure could be something like
>
> TYPE matches (
> prematch TEXT,
> match TEXT[],
> postmatch TEXT
> )

I just coded up for this:

CREATE FUNCTION regexp_matches(IN str text, IN pattern text) RETURNS
text[]
AS 'MODULE_PATHNAME', 'regexp_matches'
LANGUAGE C IMMUTABLE STRICT;

CREATE FUNCTION regexp_matches(
IN str text, IN pattern text, IN return_pre_and_post bool,
OUT prematch text, OUT fullmatch text, OUT matches text[], OUT
postmatch text) RETURNS record
AS 'MODULE_PATHNAME', 'regexp_matches'
LANGUAGE C IMMUTABLE STRICT;

Which works like this:

jeremyd=# \pset null '\\N'
Null display is "\N".
jeremyd=# select * from regexp_matches('foobarbequebaz',
$re$(bar)(beque)$re$);
regexp_matches
----------------
{bar,beque}
(1 row)

jeremyd=# select * from regexp_matches('foobarbequebaz',
$re$(bar)(beque)$re$, false);
prematch | fullmatch | matches | postmatch
----------+-----------+-------------+-----------
\N | \N | {bar,beque} | \N
(1 row)

jeremyd=# select * from regexp_matches('foobarbequebaz',
$re$(bar)(beque)$re$, true);
prematch | fullmatch | matches | postmatch
----------+-----------+-------------+-----------
foo | barbeque | {bar,beque} | baz
(1 row)

And then you also have this behavior in the matches array:

jeremyd=# select * from regexp_matches('foobarbequebaz',
$re$(bar)(.*)(beque)$re$);
regexp_matches
----------------
{bar,"",beque}
(1 row)

jeremyd=# select * from regexp_matches('foobarbequebaz',
$re$(bar)(.+)(beque)$re$);
regexp_matches
----------------
\N
(1 row)

jeremyd=# select * from regexp_matches('foobarbequebaz',
$re$(bar)(.+)?(beque)$re$);
regexp_matches
------------------
{bar,NULL,beque}
(1 row)

Reasonable?

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