newid() in postgres

marcel.beutner wrote:

I've searched in the groups already, but couldn't find any helpful
information - only to use a sequence, which returns just a number and
not a unique identifier.

Which properties do your unique identifiers posses that are not
satisfied by a number returned by a sequence?

--
Peter Eisentraut
http://developer.postgresql.org/~petere/

Marcel,

A sequence represents a unique identifier. You can call the function
'nextval' to get the next unique value in the sequence. See related
functions here:

http://www.postgresql.org/docs/8.2/interactive/functions-sequence.html

In this code, I get the next sequence, insert it into a table, and
then return the value to the calling function:

DECLARE
nextseq integer;

BEGIN
nextseq := nextval('entry_id_seq');

INSERT INTO my_table (
entry_id,
entry_text,
) VALUES (
nextseq,
p_entry_text, -- input param
);

Hello,

Thanks a lot for your answers! But I don't need a sequence which only
will be incremented. I need a _real_ GUID just as the newid()
function. Is there no way to generate such a GUID?

I need a real GUID because I use them further in my host app. And my
host app relies on it.

Thanks for your answers.

Marcel

You'll need to create a custom function in Postgres to support this,
which is fairly easy. It's been done before- do a search on Google:

http://www.hclausen.net/psql.php

Thanks,
I'll try to implement it.

Marcel

Here's a PL/pgsql implementation I wrote.....I'm sure critics will be
able to improve upon it:

CREATE or REPLACE FUNCTION "common"."newid"()
RETURNS "pg_catalog"."varchar" AS
$BODY$
DECLARE
v_seed_value varchar(32);
BEGIN
select
md5(
inet_client_addr()::varchar ||
timeofday() ||
inet_server_addr()::varchar ||
to_hex(inet_client_port())
)
into v_seed_value;

return (substr(v_seed_value,1,8) || '-' ||
substr(v_seed_value,9,4) || '-' ||
substr(v_seed_value,13,4) || '-' ||
substr(v_seed_value,17,4) || '-' ||
substr(v_seed_value,21,12));
END;
$BODY$
LANGUAGE 'plpgsql' VOLATILE SECURITY DEFINER;