Should I CLUSTER on PRIMARY KEY

[Robert James <srobertjames@xxxxxxxxx>]

I would like to CLUSTER a table on its PRIMARY KEY.  Now, I haven't explicitly defined and named an index for this table - but the primary key defines one.   How can I tell Postgres to CLUSTER on it?

Also: If I define an index on a PK, will Postgres make a second one, or realize its redundnant?

Thanks!