See the "Combiners" section of the user manual: http://accumulo.apache.org/1.6/accumulo_user_manual.html#_combiners
It does not require a compaction if the combiner is configured on all scopes; the summing will happen on the fly at scan time until it is persisted in a compaction. You can read more about scopes earlier in the same section of the manual: http://accumulo.apache.org/1.6/accumulo_user_manual.html#_iterators On Tue, May 13, 2014 at 7:02 AM, Geoffry Roberts <[email protected]>wrote: > I need to update a value, a numeric value, in Accumulo where the result is > the sum of the old and the new as opposed to the new simply replacing the > old. > > I read in a white paper that it is possible but it didn't say how. I > Googled and found a bit about Accumulo keeping a history that could be > summed. Yes, I knew about the history so I suppose that might work. But > it apparently requires compaction. Really! At first blush, this doesn't > sound like such a solid solution. > > My question is, Is this summing-of-the-history the way to achieve my > desired result or is there a better way? Either way, how do you do that? > > Thanks > -- > There are ways and there are ways, > > Geoffry Roberts >
