Re: foreign data wrappers - Mailing list pgsql-students

From Zheng Yang
Subject Re: foreign data wrappers
Date
Msg-id E7108617-4213-4C33-B5C8-D510B65EC34D@gmail.com
Whole thread Raw
In response to Re: foreign data wrappers  (Andrew Dunstan <andrew@dunslane.net>)
Responses Re: foreign data wrappers
List pgsql-students
Hi,

I managed to clone a copy of 9.1devel and compiled an binary from it. I also did a make in the 'contrib/file_fdw/' folder and a file_fdw.so file is generated.

But the following error occurs when I was trying to experiment with the file FDW:

postgres=# CREATE FUNCTION file_fdw_handler() RETURNS fdw_handler AS 'file_fdw' LANGUAGE C STRICT;
ERROR:  could not access file "file_fdw": No such file or directory
STATEMENT:  CREATE FUNCTION file_fdw_handler() RETURNS fdw_handler AS 'file_fdw' LANGUAGE C STRICT;
ERROR:  could not access file "file_fdw": No such file or directory


Did I miss anything?


ZY



On 26-Mar-2011, at 11:07 PM, Andrew Dunstan wrote:



On 03/24/2011 10:07 PM, Zheng Yang wrote:


I've briefly gone through the slides. Regarding the 6 callbacks, is that correct to say that a full table scan will always be performed irregardless of the sql statement,
the FDW is blind to the sql query performed, right?

Yes, fairly much. If the feed is large you need some way to pass a limit to the foreign side, possibly via table options. I'm fairly sure you won't be able to get it via the SELECT statement.


And can anyone help explain what a planner is? What does this "provide cost estimates to planner" mean? Thanks!


See <http://www.postgresql.org/docs/current/static/planner-optimizer.html>

If you're going to work on PostgreSQL code you need to read the docs.

cheers

andrew


pgsql-students by date:

Previous
From: Andrew Dunstan
Date:
Subject: Re: foreign data wrappers
Next
From: Guillaume Lelarge
Date:
Subject: Re: foreign data wrappers