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Re: foreign data wrappers

From: Zheng Yang <zhengyang4k(at)gmail(dot)com>
To: Selena Deckelmann <selena(at)chesnok(dot)com>, Andrew Dunstan <andrew(at)dunslane(dot)net>
Cc: pgsql-students(at)postgresql(dot)org
Subject: Re: foreign data wrappers
Date: 2011-03-24 05:39:45
Message-ID: 3EF9E4CC-CF42-4B45-86FF-4CB9D46D7442@gmail.com (view raw or flat)
Thread:
Lists: pgsql-generalpgsql-students
Hi guys,

I've figured out what a FDW does. It's quite clear from the doc that a FDW is an interface postgresql database used to communicate with
other data sources either it be a file, another DBMS or even weblinks  (please correct me if i am wrong).

I have a few more specific questions on FDW. hope you guys can help!

1) by right the FDW should be implemented by the vendor of the datasource, is that correct? 

2) what are the FDW that has been implemented? I've seen an plain file FWD module from the link provided by selena.

3) in one of the examples, when declaring an FDW,  "..LIBRARY ’foosql_fdw.so’ LANGUAGE C;"  the LANGUAGE option is going to be C only?

4) Is theFDW something similar to the Mysql storage engine architecture?

5) for the datalink, the doc has mentioned about it's going to be OS dependent. but i dun quite understand how does the kernel module and LD_PRELOAD will work in this case, esp.LD_PRELOAD.

That's the question so far. Thanks very much!

Regards,
Zheng Yang



On 22-Mar-2011, at 3:49 AM, Selena Deckelmann wrote:

> On Mon, Mar 21, 2011 at 11:45 AM, Andrew Dunstan <andrew(at)dunslane(dot)net> wrote:
> 
>> Yes, but 9.1 *has* actual FDWs. The best thing to do (other than attending
>> my talk on Thursday :-) )
> 
> :) I'll be around, so hopefully I can attend your talk and post up some notes!
> 
>> is to look at the file_fdw module in git head, to
>> see an actual working example.
> 
> I figured if I posted some wrong information someone would respond! :)
> 
> Zheng - here is a link to the existing code:
> http://git.postgresql.org/gitweb?p=postgresql.git;a=tree;f=contrib/file_fdw
> 
> -selena
> 
> -- 
> http://chesnok.com

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