Thread: Re: [GENERAL] Postgresql 8.3X supports Arrays of Composite Types?

On Sun, Apr 19, 2009 at 06:03:26PM -0300, Robson Fidalgo wrote:
> Hello,
> I am using postgresql 8.3X and I created a table (see example below)
> that has an attribute that is an Array of a Composite Type (ROW).
> However, I do not know how can I insert a record in this table.

You want a normalized table anyhow.  If you want something
denormalized, use a view.

> Example:
>
> CREATE table phone (
>   cod varchar,
>   num varchar);
>
> CREATE TABLE person (
>   name varchar,
>   telephone phone[]);

This is better as:

CREATE TABLE phone (
    cod VARCHAR,
    num VARCHAR,
    PRIMARY KEY(cod, num)
);

CREATE TABLE person (
    name varchar,
    PRIMARY KEY(name)
)

CREATE TABLE person_phone (
    name VARCHAR NOT NULL REFERENCES person(name),
    cod VARCHAR,
    num VARCHAR,
    FOREIGN KEY(cod, num) REFERENCES phone(cod, num),
    PRIMARY KEY(name, cod, num)
);

Cheers,
David.
--
David Fetter <david@fetter.org> http://fetter.org/
Phone: +1 415 235 3778  AIM: dfetter666  Yahoo!: dfetter
Skype: davidfetter      XMPP: david.fetter@gmail.com

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On Mon, Apr 20, 2009 at 08:13:15AM -0300, Robson Fidalgo wrote:
> Hi David,
>
> Thanks for your help, but I want a relational-object solution.

You can have one without denormalizing.  Just use VIEWs and rewrite
RULEs for INSERTs, UPDATEs and DELETEs on them.

> The solution presented by Tom Lane (Thanks Tom!!!!) runs very well
> and it is a relational-object implementation (I suggest put a
> similar example in postgresql 8.3X documentation).

The docs already contain an example:

http://www.postgresql.org/docs/current/static/rules-update.html

There are excellent reasons not to encourage people to do only half
the job.  One part, the smaller part, is presenting an interface which
one part of your OO code can talk to.  The other part, and the much
larger one, is having a well-indexed, normalized data store
underneath.

Example: Under the store-the-compound system you're proposing, how do
you find all the people who have a common prefix?  Answer: Normalize.
If you need that answer quickly, you're looking at down time and DDL
changes.  The questions you ask about the data are impossible to know
in advance, so normalized data helps you deal with that.

Cheers,
David.
--
David Fetter <david@fetter.org> http://fetter.org/
Phone: +1 415 235 3778  AIM: dfetter666  Yahoo!: dfetter
Skype: davidfetter      XMPP: david.fetter@gmail.com

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