Failure in PostGIS store when dealing with serial attribute

When adding a layer in geoserver against a database table that contains a serial attribute, it is impossible to submit a WFS request without specifying the serial attribute. An error is returned. The expected behaviour would be for the database to assign the next available value for the serial attribute.

What happens is that geoserver attempts to set the attribute to null. Given that a serial is mapped to a non null integer, the database can not accept the request.

In fact, the expected behaviour should be that geoserver submit a SQL request to PostGIS without specifying the missing attribute. This way, the database would perform the request correctly.

This error was found on geoserver/trunk/geoserver@8885