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The "DigestQueries" page has been changed by PeterSchuller.
http://wiki.apache.org/cassandra/DigestQueries

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New page:
A "digest" query is like a ready query except that instead of the receiving 
node actually returning the data, it only returns a digest (hash) of the 
would-be data.

The intent of submitting a digest query is to discover whether two or more 
nodes agree on what the current data is, without sending the data over the 
network. In particular for large amounts of data, this is a significant saving 
of bandwidth cost relative to sending the full data response.

Keep in mind that the cost of potentially going down to disk, and most or all 
of the CPU cost, associated with a query will still be taken on nodes that 
receive digest queries. The optimization is only for bandwidth.

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