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From Hans J Schroeder>
Subject Re: database design question: concurrent writes
Date Thu, 13 Dec 2012 16:36:00 GMT

On Dec 13, 2012, at 5:06 PM, Benoit Chesneau <> wrote:

> Hi all,
> This morning I was back reading a lot of fundamentals about  databases and
> such and was asking myself how we could increase the number of concurrent
> writes.
> These days the theory is that it will be solved by sharding the databases
> in multiples database files and merging results of the queries. Since the
> databases will be shareded then the writes on the same db will be
> concurrents. A map of the shards willl be kept aside. All of this thanks to
> the introduction of bigcouch.
> The question I have is why don't we already do that? Ie balancing datas on
> different files on one db? for example the db folder could be
> database/XY.couch
> where XY are the first letters of an id or content hash or any consistent
> hashing method.
> I am currently asking myself such question because I am wondering how will
> the backup works when couchdb will be used as a single node. How to backup
> only one db without having to query for the mapping and such? How to keep
> it it simple.
> Related to that why did bigcouch used that design? Why mapping shards in a
> db database instead of having some kind of natural balancing on the fs and
> having a consistent hashing algorithm used to balance on different
> machines/vms as well ?
> - benoƮt


That's like "horizontal partitioning" in conventional databases and I think its a great idea.
Having a writer process for each partition will make it scale.

Does Bigcouch have anything for the view files too or are they just sharding the backing files?

- Hans
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