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From: Luis Neves <lneves@netcabo.pt>
To: pgsql-sql@postgresql.org
Subject: Strange behaviour updating primary key column.
Date: Mon, 21 Jun 2004 07:29:06 +0100
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[Sorry if this is a double post.]

Hello all,

[Postgresql 7.4.2]
CREATE TABLE "story" (
"id" int4 NOT NULL,
"title" varchar (100) NOT NULL,
"body" text NOT NULL,
"entryDate" timestamptz NOT NULL,
CONSTRAINT "story_pkey" PRIMARY KEY (id)
);

In the above table why does the query:

UPDATE "story"
SET id =3D (id + 1500);

fails with:
"ERROR:=A0=A0duplicate=A0key=A0violates=A0unique=A0constraint=A0'story_pkey=
'"

(I have 6000 records in the table with "id" spanning from 1 to 6000)

I find this behaviour strange, SQL is a set based language, but=20
PostgreSQL is acting like is changing the values in sequence.

Can anyone with a better understanding of PostgreSQL explain to me why this
happens?
Are my expectations wrong?


Best regards,
Luis Neves