Returning the name of a primary key

On Mon, May 16, 2005 at 01:25:46PM -0500, Juan Pablo Espino wrote:

I need to write a function that retrieve the name of at least one
table primary key, if it exists. The only argument passed to the
function is the table name. I have thought something like this:

Why mess around with a C function, if you can do it in straight SQL?
You can write a SQL function if need be.

--
Alvaro Herrera (<alvherre[a]surnet.cl>)
Voy a acabar con todos los humanos / con los humanos yo acabar�
voy a acabar con todos / con todos los humanos acabar� (Bender)

Juan Pablo Espino <jp.espino@gmail.com> writes:

I need to write a function that retrieve the name of at least one
table primary key, if it exists. The only argument passed to the
function is the table name. I have thought something like this:

You need to be searching the list of indexes, not the attributes per se.
ATExecDropNotNull() might be a useful example.

regards, tom lane

On Mon, May 16, 2005 at 02:35:03PM -0400, Alvaro Herrera wrote:

On Mon, May 16, 2005 at 01:25:46PM -0500, Juan Pablo Espino wrote:

I need to write a function that retrieve the name of at least one
table primary key, if it exists. The only argument passed to the
function is the table name. I have thought something like this:

Why mess around with a C function, if you can do it in straight SQL?
You can write a SQL function if need be.

http://lnk.nu/cvs.pgfoundry.org/2op.sql is an example of how to get the
info in pure SQL.
--
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Tom, Juan,

Wouldn't this simple SQL do the trick?

CREATE OR REPLACE FUNCTION pk_column(text) RETURNS SETOF text
AS '
SELECT attname::text
FROM pg_class, pg_constraint, pg_attribute
WHERE pg_class.oid = conrelid
AND contype=''p''
AND attrelid = pg_class.oid
AND attnum = ANY (conkey)
AND relname=$1;
'
LANGUAGE sql VOLATILE STRICT;