Re: Absolute value of intervals

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Sam Mason <sam(at)samason(dot)me(dot)uk>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Absolute value of intervals
Date: 2009-10-27 14:55:31
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Sam Mason <sam(at)samason(dot)me(dot)uk> writes:
> On Tue, Oct 27, 2009 at 11:27:17AM -0300, Joshua Berry wrote:
>> I couldn't find the operator '@' for intervals

> A simple SQL implementation would look like:

> CREATE FUNCTION absinterval(interval) RETURNS interval
> IMMUTABLE LANGUAGE sql AS 'SELECT greatest($1,-$1)';
> CREATE OPERATOR @ ( PROCEDURE = absinterval, RIGHTARG = interval );

> or is a C version really needed?

I think this came up again recently and somebody pointed out that the
correct definition isn't as obvious as all that. The components of
an interval can have different signs, so should abs('-1 day 1 hour') be
'1 day -1 hour' or '1 day 1 hour'? Or what about corner cases like
'1 day -25 hours'?

regards, tom lane

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