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Re: [HACKERS] Function-manager redesign: second draft (long)

From: Hannu Krosing <hannu(at)tm(dot)ee>
To: Jan Wieck <wieck(at)debis(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, maillist(at)candle(dot)pha(dot)pa(dot)us, pgsql-hackers(at)postgreSQL(dot)org
Subject: Re: [HACKERS] Function-manager redesign: second draft (long)
Date: 1999-10-30 21:39:54
Message-ID: 381B65AA.9374CE7B@tm.ee (view raw or flat)
Thread:
Lists: pgsql-hackers
Jan Wieck wrote:
> 
>     Another  detail  I'm  missing  now  is  a new, really defined
>     interface for type input/output functions. The fact that they
>     are  defined  taking  one  opaque  (yepp, should be something
>     different as already discussed) argument but in fact get more
>     information from the attribute is ugly.

Can we currently return a list of the same type ?

I guess we can, as lists (or arrays) are fundamentl types in 
PostgreSQL, but I'm not sure.

I would like to define aggregate functions list() and set()

Could I define then just once and specify that they return an array 
of their input type ?

Half of that is currently done for count() - i.e. it can take any 
type of argument, but I guess the return-array-of-input-type is more 
complicated.




Also (probably off topic) how hard would it be to add another type 
of aggregate funtions tha operate on pairs of values ?

I would like to have FOR_MIN and FOR_MAX (and possibly MIN_MIN and
MAX_MAX) functions that return _another_ field from a table for a 
minimal value in one field.

-------------
Hannu

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