----- Original Message -----
From: "Darren Duncan" <dar...@darrenduncan.net>
To: "Jaime Casanova" <ja...@2ndquadrant.com>
Cc: "PostgreSQL-development" <pgsql-hackers@postgresql.org>
Sent: Saturday, May 14, 2011 9:46 PM
Subject: Re: [HACKERS] DOMAINs and CASTs
Darren Duncan wrote:
I think it would be best that the generic cast syntax only be useable for
casts defined on the base type, and if you want a domain-specific one you
should use the function syntax such as your datetime2int().
That way it is easier for users to predict what behavior will occur, and
implementation will be easier too.
Replying to myself, I offer another alternative:
What you ask for is indeed supported, but that if for a given input value
more than one cast applies to it, particularly for 2 overlapping domains,
then which cast is invoked is undefined, so for example the DBMS may just
use the first one it finds.
It is then up to the user to ensure that when they define casts over
domains that they just define ones that either produce the same outputs
for the same overlapping inputs (the best answer) or they ensure that they
don't overlap in their input domains.
-- Darren Duncan
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