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From Antony Blakey <>
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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