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From Antony Blakey <antony.bla...@gmail.com>
Subject Re: couchdb (_external consistency issues and proposals)
Date Mon, 22 Dec 2008 08:51:59 GMT

On 22/12/2008, at 5:14 PM, Antony Blakey wrote:

> I now know that this is wrong, sorry. Document deletions are never  
> 'lost', and hence there's no need to track compaction generations.  
> That raises a very different issue I noted in 'History of deletion,  
> and the interaction with compactions' on couchdb-dev, but it's  
> nothing to do with _external.

Hmmm. Further digging reveals that the purge function will in fact  
remove the record of deletions. Luckily there's a purge_seq value  
supplied in the dbinfo result (and also in each _external call). By  
tracking this, an _external knows when to revalidate it's documents.

Purging can break replication, especially in distributed systems  
without centralized knowledge or control of replication status (which  
is my situation).

Antony Blakey
--------------------------
CTO, Linkuistics Pty Ltd
Ph: 0438 840 787

Lack of will power has caused more failure than lack of intelligence  
or ability.
  -- Flower A. Newhouse


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