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From "Perko, Ralph J" <Ralph.Pe...@pnnl.gov>
Subject recursive rollup
Date Tue, 10 Apr 2012 22:02:32 GMT
Hi, I wish to do a recursive rollup-count and am wondering the best way to
do this.

What I mean is this ­ in accumulo is a table with data that represents the
nodes and leafs in a tree.  Each node/leaf in accumulo knows it's parent
and children and wether it is a node or leaf.  I wish to have a
rollup-count for any given node to know the combined total of all
descendants.

For example, given the tree:

                          A
                          |
                       --------
                       |      |
                       B      C
                       |      |
                     -----  -----
                     |   |  |    |
                     D   E  F    G

"A" would have 6 descendants.

I can use the SummingCombiner iterator to get a child count, e.g "A" has 2
children, but I am not sure the best way to recurse down.  The data is
static so I do not necessarily need a dynamic, on-the-fly solution.

Thanks for your help,
Ralph


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