I am having a problem migrating a database from Informix to PostgresSQL due to differences in the behaviour of the SERIAL fields in postgres.

In informix, if I pass a '0' to a serial field (e.g. a record index) I am given the next available value in the field automatically.

As far as I can tell from postgres the same thing should happen. Postgres creates a sequence for the serial field and sets the default value as:

nextval('"count_idx_seq"'::text)

however if I try to enter a 0 to the list, 0 gets added to the table, then future inputs return a "duplicate value not allowed" error.

Any tips?

Dan