check constraint question - Mailing list pgsql-general

Hi All

we have a table like so:


customer (
cust_id                     integer not null primary key,
cust_group_id          integer not null,
group_account_id    integer not null,
cust_name               varchar not null,

...
)

we want to force the cust_group_id to be unique across all
group_account_id's but not necessarily across the entire table

I assume the best approach would be a check constraint yes? Will this be
excessively poor per performance if the table gets big?

Thoughts?

Thanks in advance