Message-ID: <4019486E.7000807@joeconway.com>
Date: Thu, 29 Jan 2004 09:52:46 -0800
From: Joe Conway <mail@joeconway.com>
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To: Chris Travers <chris@travelamericas.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: How to retrieve N lines of a text field.
References: <010301c3e679$077698b0$5444053d@winxp>
In-Reply-To: <010301c3e679$077698b0$5444053d@winxp>
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Chris Travers wrote:
> This is a complex issue, and i am tryign to figure out how to use regular
> expressions to resolve this issue.  I need to retrieve the first N lines of
> a text field.  N would be assigned using a parameterized query, if possible.

How 'bout something like this:

CREATE OR REPLACE FUNCTION first_n_lines(text, int)
RETURNS setof text AS '
DECLARE
   i int := 0;
   oneline text;
BEGIN
   LOOP
     i := i + 1;
     IF i > $2 THEN
       EXIT;
     END IF;
     SELECT INTO oneline split_part($1, ''\n'', i);
     IF oneline = '''' THEN
       EXIT;
     END IF;
     RETURN NEXT oneline;
   END LOOP;
   RETURN;
END
' LANGUAGE 'plpgsql';

regression=# select * from first_n_lines('abc\ndef\nghi', 2);
  first_n_lines
---------------
  abc
  def
(2 rows)

HTH,

Joe