2011/11/28 Shigeru Hanada <shigeru.hanada@gmail.com>:
> I agree that allowing users to control which function/operator should be
> pushed down is useful, but GUC seems too large as unit of switching
> behavior. "Routine Mapping", a mechanism which is defined in SQL/MED
> standard, would be the answer for this issue. It can be used to map a
> local routine (a procedure or a function) to something on a foreign
> server. It is like user mapping, but it has mapping name. Probably it
> would have these attributes:
>
> pg_catalog.pg_routine_mapping
> rmname name
> rmprocid regproc
> rmserverid oid
> rmfdwoptions text[]
>
> If we have routine mapping, FDW authors can provide default mappings
> within extension installation, and users can customize them. Maybe FDWs
> will want to push down only functions/operators which have routine
> mapping entries, so providing common routine which returns mapping
> information of given function/operator, say GetRoutineMapping(procid,
> serverid), is useful.
>
> Unfortunately we don't have it at the moment, I'll fix pgsql_fdw so that
> it pushes down only built-in operators, including scalar-array operators.
One difficulty here is that even very simple operators don't
necessarily mean the same thing on both sides. In my last job we had
a Microsoft SQL database where string equality was case insensitive,
and a PostgreSQL database where it wasn't.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
