Question

in the database there are many identical schemas, cmp01..cmpa0

each schema has a users table

each schema’s users table’s primary key has its own unique range

for example, in cmp01.users the usr_id is between 0x01000000 and 0x01ffffffff.

is there any way I could define a VIEW global.users that is a union of each of the cmp*.union tables in such a way that, if querying by usr_id, the optimizer would head for the correct schema?

was thinking something like:

create view global.users as
select * from cmp01.users where usr_id between 0x01000000 and 0x01ffffffff
union all
select * from cmp02.users where usr_id between 0x02000000 and 0x02ffffffff
....

would this work? NO. EXPLAIN ANALYZE shows all schema used.

Is there an approach that might give good hints to the optimizer?

Answer 1

What about creating a partitioned table? The master table would be created as global.users and it would be partitioned by the schema name.

That way you’d get the small user tables in each schema (including fast retrievals) provided you can create queries that PostgreSQL can optimize i.e. including the schema name in the where condition. You could also create a view in each schema that would hide the needed schema name to query the partitioned tables. I don’t think it would work by specifying only the user_id. I fear that PostgreSQL’s partitioning features are not smart enough for that.

Or use just one single table, and create views in each schema with an instead of trigger and limiting the result to that schema’s users.