From: Bruce Momjian <pgman@candle.pha.pa.us>
Message-Id: <200310311949.h9VJn0J04943@candle.pha.pa.us>
Subject: Re: Annotated release notes
In-Reply-To: <3FA1F902.7000407@joeconway.com>
To: Joe Conway <mail@joeconway.com>
Date: Fri, 31 Oct 2003 14:49:00 -0500 (EST)
Cc: Tatsuo Ishii <t-ishii@sra.co.jp>, peter_e@gmx.net,
	neilc@samurai.com, chriskl@familyhealth.com.au, tgl@sss.pgh.pa.us,
	pgsql-hackers@postgresql.org,
	PostgreSQL-documentation <pgsql-docs@postgresql.org>
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Joe Conway wrote:
> Bruce Momjian wrote:
> > 	http://candle.pha.pa.us/main/writings/pgsql/sgml/release.html#RELEASE-7-4
> > 
> > I need people to check this and help me with the items marked 'bjm'.  I
> > am confused about the proper text for those sections.
> 
>  > Allow polymorphic SQL functions (Joe)
>  > bjm ??
> 
> What isn't clear about this? Should/can we refer to related sections of 
> the manual?
> http://developer.postgresql.org/docs/postgres/xfunc-sql.html#AEN28722
> http://developer.postgresql.org/docs/postgres/extend-type-system.html#EXTEND-TYPES-POLYMORPHIC
> 
>  > Allow user defined aggregates to use polymorphic functions (Joe)
>  > bjm ??
> 
> Same question. From this url:
> http://developer.postgresql.org/docs/postgres/xaggr.html
> see this paragraph:
> 
>   Aggregate functions may use polymorphic state transition functions or 
> final functions, so that the same functions can be used to implement 
> multiple aggregates. See Section 33.2.1  for an explanation of 
> polymorphic functions. Going a step further, the aggregate function 
> itself may be specified with a polymorphic base type and state type, 
> allowing a single aggregate definition to serve for multiple input data 
> types. Here is an example of a polymorphic aggregate:
> 
> CREATE AGGREGATE array_accum (
>      sfunc = array_append,
>      basetype = anyelement,
>      stype = anyarray,
>      initcond = '{}'
> );

What had me really confused was the first release item:

	Allow polymorphic SQL functions (Joe)

How does an SQL function query the data types passed to it?  Once I saw
that I thought I didn't underestand what polymorphic functions were.

Right now we have:
	
	<listitem><para>Allow user defined aggregates to use polymorphic functions (Joe)</para>
	   <para>
	    bjm ??
	   </para>
	   </listitem>
	<listitem><para>Allow polymorphic user defined aggregates  (Joe)</para></listitem>

These seem like duplicates.  Are polymorphic functions currently most
useful for aggregates?  Why would someone want polymorphic aggregates? 
That is what I was hoping for.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
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