[development] Why do we avoid auto-incrementing db columns?

[Barry Jaspan]

Sammy Spets <sammys-drupal at synerger.com> writes:
> PostgreSQL [has] serial and bigserial types. MySQL [has] auto_increment
> field property. These are used in Drupal to produce a guaranteed
> unique ID for tables using them.
> 
> We use db_next_id() in Drupal to provide a db-independent method of
> getting the next unique ID into the application for use just after the
> insert operation on the DB.

I interpret this to mean, in your opinion at least, that (a) Drupal
does officially condone and support the use of auto-incrementing
columns and (b) it also provides db_next_id() for those situations
where having it is simply more convenient or efficient than letting
the database do the id generation.

Is that correct?  Is this the official core policy on this subject?

> I'm PostgreSQL maintainer for Drupal...

FYI, the Schema module now supports MySQL and PostgeSQL for table and
index creation from the same schema data structure.  I discovered the
pgsql's use of the serial type during the implementation which is what
led to my initiating this thread.  Schema now supports a 'serial'
column type which maps to auto_increment for MySQL or {,big}serial for
PostgreSQL.

I'd be very happy to have you review the pgsql support.  Schema is
currently in contrib.

Thanks,

Barry