Now you're getting to the technical part. This quote from Damien is the best I can do for you: http://damienkatz.net/2008/02/incremental_map_1.html ... in this design, the reductions happen at index-update time, and the reductions are stored directly inside the inner nodes of the view b+tree index. Then at query time, the intermediate results are reduced to their final result. The number of reductions that happen at query time are logarithmic with respect to the number of matching key/values.
So for modifications and deletions, the map results are changed, the tree of intermediate values is partially dirty, and the reduction only has to be partially re-done.
Very cool.
