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From Robert Dionne <dio...@dionne-associates.com>
Subject Re: Has Erlang's promise of parallelism been realised in CouchDB?
Date Thu, 30 Jun 2011 11:38:30 GMT
the reductions are stored as part of the btree nodes. the btree is append-only so a new branch
from the leaves to the root is created
when writes occur. The reduce and rereduce functions are called along the way to compute the
reductions and they are stored with 
the nodes. 

CouchDB uses a fixed chunk size, to break up the list of nodes to write into chunks. This
determines the branching. So basically the nodes
in the btree have no capped or fixed size, they will vary with the size of the keys and the
reductions. In general one wants a high branching
factor, making for shallower trees.

by internal I mean non-leaf nodes. 



On Jun 30, 2011, at 7:10 AM, Dirkjan Ochtman wrote:

> On Thu, Jun 30, 2011 at 12:38, Robert Dionne
> <dionne@dionne-associates.com> wrote:
>>  I think one thing that really impacts performance with the view indexer is the storing
of the reductions
>> in the internal nodes of the btree.
> 
> What do you mean by internal, here? Do you mean that they shouldn't be
> stored at all, or that they should be stored separately somehow?
> 
> (Alternatively: this sounds interesting, please explain what you mean.)
> 
> Cheers,
> 
> Dirkjan


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