Upgrading schemas - Mailing list pgsql-general

Hi,

I have an application using Postgresql with a large (100+) number of
tables.  Are there any free/open source tools that can ease the process
of updating the schema.

Specifically I would like to compare a source and a target, determine
the differences and the best way to update  the target to be equivalent
to the source - tables, columns, views, etc.

thanks