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Cc: Guillaume Lelarge <guillaume@lelarge.info>,
	Selena Deckelmann <selena@chesnok.com>,
	Andrew Dunstan <andrew@dunslane.net>,
	pgsql-students <pgsql-students@postgresql.org>
Subject: Re: foreign data wrappers
From: Alvaro Herrera <alvherre@commandprompt.com>
To: Zheng Yang <zhengyang4k@gmail.com>
In-reply-to: <4ACC318A-1B6F-49A5-9B02-49EEAF7B97C7@gmail.com>
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Date: Thu, 24 Mar 2011 13:49:02 -0300
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Excerpts from Zheng Yang's message of jue mar 24 05:49:19 -0300 2011:

> I am quite new to postgresql, but slowly picking up :)  In general context, storing images directly inside DBMS fields as BLOBs was not considered as a good practice. 
> However, storing file directories  or links may cause inconsistency. So I am quite interested in how this datalink concept can be implemented! 

I'm not really sure how different would be handling the file linking in
an FDW.  For example, if a transaction runs that deletes a file through
the FDW, and the transaction rolls back, how are you going to restore
the file to life?

(It sounds like you're trying to have a FDW that would present a
directory as a table, and each file in the dir as a row.  Maybe it's not
a bad idea but it needs a lot more thought.)

-- 
Álvaro Herrera <alvherre@commandprompt.com>
The PostgreSQL Company - Command Prompt, Inc.
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