Re: Object Relational features in PostgreSQL

This will be the topic of a talk I'll be giving at OSCON in July.

The extent of Object implementation in PostgreSQL
is not as simplistic as your analysis makes it. The Object
side of object-relational includes creating datatypes which in
turn are first class objects to be used in a relational database system.
Those first class objects have structure (class), functions
(methods, operators and indexes). The relatively recent addition
of DOMAIN support enable creating subclasses of existing types,
usually base types.

PG's implementation of inheritance is not a full OO
definition of inheritance and is contrary to Codd&Date&Darwin's
specifications for inheritance. There were other ORDBMS that did
differently or to deeper extents.

For a good understanding of some of the features you are mentioning
and as a comparison to PostgreSQL's implementation see
Paul G. Brown's book "Object-Relational Database Management: A Plumber's Guide".

I would be happy to help with additional information about the
extent of the O part or ORDBMS to help your management team.

elein
============================================================
elein(at)varlena(dot)com Varlena, LLC www.varlena.com

PostgreSQL Consulting, Support & Training

PostgreSQL General Bits http://www.varlena.com/GeneralBits/
=============================================================
"Sometimes we are confronted with more data than we can really use,
and it may be wisest to forget and to destroy most of it"
-- Donald Knuth, The Art of Computer Programming

On Mon, Jan 26, 2004 at 10:01:19AM +0200, Robert Abi Saab wrote:
> Hi everyone. I just finished a course on PostgreSQL and I found out that
> PostgreSQL doesn??t provide any object relational features (as claimed in the
> official documentation), except table inheritance and very limited user defined
> types (I defined a UDT with 2 attributes and couldn??t use it in a table, and
> the trainer said it must contain 1 attribute at most so that it can be used (as
> a column) in tables)
>
>
>
> So my question is whether there is (or will be) any support for (any of) the
> following:
>
> More flexible user defined types and support for these in tables
>
> Type inheritance
SEE Domains
>
> REF and DEREF data types
>
See OIDS

> Nested tables
>
See row types and/or arrays. Row types are not currently valid
to store in a column.

> Polymorphism and more flexible casting of objects (like the TREAT function, not
> only the ONLY function)
>
> Typed tables (create table X of type Y)
>
See named types.

> Object views
>
We have this but you may not recognize it as such.

> User defined functions (encapsulated in the body of a user defined type)
>
This is an implementation detail. The functions are linked to
the type in the type definition.
>
>
> I would be really thankful for any fast reply, because I need to report to the
> management whether a migration to PostgreSQL is both efficient and possible or
> not.
>

>
>
>
>
>
>