Re: PL/pgSQL & OVERLAPS operator

In response to Tuo Pe :
> Hello!
>
> I am teaching myself PL/pgSQL. I am trying to write a function that tests whether two time periods overlap. I want to test the function parameters against these two values in "overlaptest" table:
>
> select * from overlaptest;
> id | alku | loppu
> ----+---------------------+---------------------
> 1 | 2010-03-23 10:00:00 | 2010-03-23 12:00:00
> (1 row)
>
> I have written this function,
>
> CREATE OR REPLACE FUNCTION TryOverlap(text, text) RETURNS boolean AS $$
> DECLARE
> ts_start timestamp with time zone := CAST ($1 AS TIMESTAMP WITH TIME ZONE);
> ts_end timestamp with time zone := CAST ($2 AS TIMESTAMP WITH TIME ZONE);
> alku timestamp with time zone;
> loppu timestamp with time zone;
> BEGIN
> SELECT alku,loppu FROM overlaptest WHERE id = 1 INTO alku,loppu;
> IF ((alku,loppu) OVERLAPS (ts_start,ts_end)) THEN
> RETURN true;
> END IF;
> RETURN false;
> END;
> $$ LANGUAGE plpgsql;
>
> However, it always seems to return the value false. What's the problem here?

You have alku and loppu as variable and as table-column, that's a bad
idea, maybe that's an error, i'm not sure.

Btw.: you can use the PERIOD-datatype:

11:16 < akretschmer> ??period
11:16 < pg_docbot_adz> For information about 'period' see:
11:16 < pg_docbot_adz> http://wiki.postgresql.org/wiki/RangeTypes
11:16 < pg_docbot_adz> http://pgfoundry.org/projects/temporal
11:16 < pg_docbot_adz> http://github.com/davidfetter/PostgreSQL-Temporal

And 9.0 contains a new feature: exclusion constraints:
http://www.depesz.com/index.php/2010/01/03/waiting-for-8-5-exclusion-constraints/

Andreas
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Andreas Kretschmer
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