PostgreSQL catalogues: how to find the primary key?

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I've been trying to get Keystone (http://www.stonekeep.com/keystone/)
up and running. The PHP script it uses are really oriented to MySQL,
although there is a mostly complete set of PostgreSQL functions
written for it. One thing missing is a query to find the primary key
on a table.

What catalogues do I need to query to find this? Is there some
documentation on the catalogues (I didn't find any, but....).

On a similar note, I've managed to figure out how to find column
widths but looking at the pg_attribute table and subtracting 4 from
the value of atttypmod for strings, including char(). However, that
was slightly non-obvious. The "old" PHP scripts looked at the attlen
column which no longer seems to apply...am I doing the right thing
here?

roland

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Roland B. Roberts, PhD Custom Software Solutions
roberts(at)panix(dot)com 101 West 15th St #4NN
New York, NY 10011