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Re: Type Categories for User-Defined Types

From: "David E(dot) Wheeler" <david(at)kineticode(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Type Categories for User-Defined Types
Date: 2008-07-31 17:42:00
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Lists: pgsql-hackers
On Jul 30, 2008, at 13:10, Tom Lane wrote:

>> Yes, that was essentially my point. "arbitrary string of text" types
>> are probably fairly rare, since one can just use text or citext or
>> varchar.
> Good point --- so new members of STRING category aren't going to be  
> that
> common, except for domains which apparently aren't bothering people
> anyway.  I'll go ahead and make the change.  (I think it's just a
> trivial change in find_coercion_pathway, and everything else should
> Just Work.  If it turns out not to be trivial maybe we should
> reconsider.)

Wow. Really nice, Tom. Thanks!

The attached patch has all the tests I added to my svn version against  
8.3, and for which I had to write 60 additional cast functions. With  
your changes, I had to add only two more:

RETURNS citext
AS 'booltext'

RETURNS citext
AS 'SELECT text( $1 )::citext'

So the I/O casts are working beautifully. This is true even for ENUMs,  
which I couldn't get to magically cast with a function in 8.3. Thank  

If you don't want so many cast tests, I can remove all but a few of  
them. I wrote them for all the core user-visible types I could  
identify so that I could see how they behaved with text and then make  
citext work the same way. Such is not as important in HEAD, thanks to  
the I/O casting, so let me know if you want me to cut down on the  
number of tests (I was particularly uncertain about the xml type,  
since --with-libxml won't always be true, I expect).

The other change in this patch is the addition of functions to make  
various string-comparison functions behave case-insensitively. I've  
started with all those that I was aware of from the previous  
documentation, and I've made them behave case-insensitively by writing  
SQL functions to hack it in. Ideally these would be done in C, but  
that started to get beyond my abilities. Suggestions welcome.

The only other thing I wanted to look at doing with citext was to look  
for any other string-comparison functions I might have missed and do  
the same for them. Otherwise, I think we're golden.

Many thanks,


Attachment: citext_casting.patch.gz
Description: application/x-gzip (8.8 KB)

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