[jakobe]

One compelling use case I've heard for schemas is versioning.

Say you want to upgrade a stored function in your database. You need to make sure that both the new and the old version of the function are available until all application code that uses the stored procedure has been updated.

Without schemas, you'd have to add a version identifier to each function, like get_customer_5(), get_customer_6() etc.

With schemas, you can just put different versions of the functions into different schemas, and just change the search_path in your application code to use functions from the new schema. When all application code has been updated, you can drop the old schema.