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From: Richard Huxton <dev@archonet.com>
Organization: Archonet Ltd
To: Andreas Tille <tillea@rki.de>,
	PostgreSQL SQL <pgsql-sql@postgresql.org>
Subject: Re: Explicite typecasting of functions
Date: Wed, 14 Aug 2002 12:10:29 +0100
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On Wednesday 14 Aug 2002 10:30 am, Andreas Tille wrote:
> Hello,
>
> I want to insert new data into a table with increasing data set ids.
> The table has two separate "regions" of data: Those with Ids below
> 1000000 and other.  If I want to create a new Id in the "lower region"
> I tried the following (simplified example):
>
>
> CREATE TABLE Items (
>   Id    int DEFAULT NextItem()

> CREATE FUNCTION NextItem() RETURNS INT4
>     AS 'select max(Id)+1 from Items where Id < 1000000;'
>     LANGUAGE 'sql';

>    ERROR:  Relation "items" does not exist
>
> Any hint to solve this kind of chicken-egg-problem?

Your solution is not safe anyway - you could end up with two processes tryi=
ng=20
to insert the next value.

Can I suggest two sequences: item_low_seq and item_high_seq? Set the initia=
l=20
value of each to 1,000,000 and 99,000,000 (or whatever) and then use=20
whichever sequence is appropriate.

In the example above you'd want something like:
  id int not null default nextval('item_low_seq')

- Richard Huxton