Re: Annotated release notes

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.

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