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Re: BLOBs and a virtual file system

From: Frank Wiles <frank(at)wiles(dot)org>
To: Peter Martini <peterm(at)processflo(dot)com>
Cc: tgl(at)sss(dot)pgh(dot)pa(dot)us, pgsql-hackers(at)postgresql(dot)org
Subject: Re: BLOBs and a virtual file system
Date: 2004-06-23 19:16:51
Message-ID: 20040623141651.336781c1.frank@wiles.org (view raw or flat)
Thread:
Lists: pgsql-hackers
On Wed, 23 Jun 2004 15:07:42 -0400
Peter Martini <peterm(at)processflo(dot)com> wrote:

> I'm not sure what you mean by breaking blobs transactional integrity. 
> Do you mean by allowing filesystem type access, the blobs won't be
> properly locked and updated during a transaction?  If so, that's
> exactly what I'm trying to achieve - a compromise between forcing the
> files to be stored solely in the database (maintaining integrity but
> sacrificing functionality) or referencing their names to gain
> functionality, but at a greater cost.
> More to the point, wouldn't file locking mechanisms, and the
> possibility of limiting file visibility through the virtual
> filesystem, allow transactional integrity to be maintained?  If not,
> could you explain where the problem is so I can look further into it?

  I believe the problem is that the blob could be in several different
  states inside of several different transactions. How do you 
  determine which you show in the filesystem? 

  Even if the file system is read only you still have this problem of
  "which" of the many possible BLOBs to reveal.  

 ---------------------------------
   Frank Wiles <frank(at)wiles(dot)org>
   http://frank.wiles.org
 ---------------------------------


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