From: | Zheng Yang <zhengyang4k(at)gmail(dot)com> |
---|---|
To: | Andrew Dunstan <andrew(at)dunslane(dot)net> |
Cc: | Shiv <rama(dot)theone(at)gmail(dot)com>, Selena Deckelmann <selena(at)chesnok(dot)com>, Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Guillaume Lelarge <guillaume(at)lelarge(dot)info>, pgsql-students <pgsql-students(at)postgresql(dot)org> |
Subject: | Re: foreign data wrappers |
Date: | 2011-03-27 12:51:21 |
Message-ID: | E7108617-4213-4C33-B5C8-D510B65EC34D@gmail.com |
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Lists: | pgsql-general 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
>
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