From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
---|---|
To: | Shigeru Hanada <shigeru(dot)hanada(at)gmail(dot)com> |
Cc: | Kohei KaiGai <kaigai(at)kaigai(dot)gr(dot)jp>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Hitoshi Harada <umi(dot)tanuki(at)gmail(dot)com>, Martijn van Oosterhout <kleptog(at)svana(dot)org>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: pgsql_fdw, FDW for PostgreSQL server |
Date: | 2011-11-28 13:59:31 |
Message-ID: | CA+TgmoYpLHCFv44aHjp7=qzSempKJcyxC6L5eXi_GDtQcLrScw@mail.gmail.com |
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2011/11/28 Shigeru Hanada <shigeru(dot)hanada(at)gmail(dot)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
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