On Mon, Apr 06, 2009 at 07:46:37AM -0700, Adam Wolff wrote: > I'm still not quite clear on > the meaning of this: > "reduce functions should not grow its output larger than log(n) where n is > the number of input rows" > > How is the size of the output measured? length of the JSON string? are > the input rows > the size of the value emitted by the map?
I don't know the details - I just copy-pasted that from the wiki. > Does this mean it's wrong to > have an entry in > your reduce output for every map key? I believe that's the case. The reduce output forms a tree overlaid onto the document Btree: each Btree node contains N documents plus a single reduce value from those N documents. The Btree could be multiple levels deep, and you don't want to end up with a single enormous value in the root node. But I don't know what that actual size limit is. Regards, Brian.
