Re: WIP: Range Types

From: Jeff Davis <pgsql(at)j-davis(dot)com>
To: David Fetter <david(at)fetter(dot)org>
Cc: Hitoshi Harada <umi(dot)tanuki(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: WIP: Range Types
Date: 2011-01-06 17:32:29
Message-ID: 1294335149.18031.3524.camel@jdavis
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On Wed, 2011-01-05 at 12:07 -0800, Jeff Davis wrote:
> The current design for range types doesn't ask for add or subtract.
> Although it might be interesting to try to use such an interface for
> range types, it introduces a lot of complexity and makes it easier to
> cause subtle problems (consider that addition of timestamps and
> intervals is not commutative).

A consequence of this design is that some generic range functions, like
"length" or "distance" would need to rely on the polymorphism of "+" and
"-" to work.

I'm also not sure if a constructor like "range(start, offset) returns
anyrange" could be made to work generically at all, because the start
and offset may be two different types (and a function that takes
ANYELEMENT requires that all ANYELEMENT arguments are the same type).

Does anyone see a problem with that?

Regards,
Jeff Davis

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