On Fri, Mar 16, 2012 at 4:44 AM, Etsuro Fujita <fujita.ets...@lab.ntt.co.jp> wrote: > I have a plan to support 'Create index on foreign table' for 9.3. Here > is my plan. > > The index creation is supported for a flat file such as CSV and a remote > table on a RDB e.g., Postgres using CREATE INDEX. (I thought using a > new statement, CREATE FOREIGN INDEX, at first, but I think that CREATE > INDEX would be sufficient to define an index for the foreign table.) > For a flat file, CREATE INDEX constructs an index in the same way as an > index for a regular table.
It seems really weird to have the data half inside the database and half outside of it like this. What is the use case for this feature? I would have thought that something like file_fdw would be primarily targeted toward use cases where you intend to read the data file only a few times, or you always intend to sequential scan it. If you need to index it, why not store the data in a regular table? That's what they are for. What you're proposing sounds to me like a lot of work for no real gain. > On the other hand, for a remote table, > CREATE INDEX collects information about the index on the specified > column(s) for the specified table that was created on the remote table. I can possibly see the point of this. Having local information about which remote indexes are available seems like it could be useful. As Heikki says, you could cache it on a per-session basis, but that might not be very efficient. I also think that it would not be a very good idea to have CREATE INDEX on a foreign table sometimes really create an index and other times just define the properties of a remote index. If we're going to have both features at all, I think they should use different syntax. I suggest that CREATE INDEX or CREATE FOREIGN INDEX is the right way to provide the query planner with information about remote-side indexes; and that if we even want to have indexes on flat files, the interface to those should be exported via functions bundled in the file_fdw extension rather than DDL. There's no reason to suppose that the indexes the FDW supports correspond to PostgreSQL's AMs, so tying it into that framework doesn't seem wise. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers