From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
Cc: | Peter Eisentraut <peter_e(at)gmx(dot)net>, PG Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Distinct types |
Date: | 2008-11-28 16:49:17 |
Message-ID: | 26955.1227890957@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Simon Riggs <simon(at)2ndQuadrant(dot)com> writes:
> On Fri, 2008-11-28 at 11:20 -0500, Tom Lane wrote:
>> If it's going to take a significant amount of work then I think someone
>> ought to provide an actual justification why it's worth the work.
> Few thoughts:
> * Domains don't work very well in conjunction with arrays.
But distinct types would somehow work better?
> * Strong typing is preferable in complex applications to avoid errors
> like sum(ordinal_column). Most developers use this all the time in their
> 3GL code but cannot use it in SQL.
The problem I see with distinct types is that the typing is *too*
strong --- the datatype has in fact got no usable operations whatever.
> * Allows migration of code easier from places that use strange sounding
> datatypes that can be mapped easily to existing datatypes.
Again, distinct types do *not* provide a "mapping to existing types",
because none of the operations carry along. Domains would be more
nearly what you want for that.
regards, tom lane
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