Aggregate data with multi-schema tenant architecture

We have an application that uses the tenant schema architecture, one database, has multiple schema per "tenant", each tenant is a replica with same tables etc. Sometimes we don't know the tenant or have to make global stats, in both case we need the aggregate of a table from each tenant. The solution is a stored procedure that will create a view, the view is generated by looping over the tenant names, querying from it and using an union. The view's definition ends up being something like : select * from tenant1.table union all ... select * from tenant2.table etc. The stored procedure is ran every night in case a new tenant is added to update the view's declaration. First request on the view is always slow (more than 1 minute) but then cache hits and it takes 3 seconds. Optimizations have been done on the where clauses of the request by adding indexes, as well as union all instead of using union since duplicates are impossible. I was wondering if there were better ways, performance-wise to do multi-tenant data aggregates ? Database => tenant1_schema => actors, table2, ... tenant2_schema => actors, table2, ... ... public_schema => aggregateview