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From kurt greaves <>
Subject Re: load distribution that I can't explain
Date Tue, 12 Sep 2017 01:25:13 GMT
Your first query will effectively have to perform table scans to satisfy
what you are asking. If a query requires ALLOW FILTERING to be specified,
it means that Cassandra can't really optimise that query in any way and
it's going to have to query a lot of data (all of it...) to satisfy the
Because you've only specified one attribute of the partitioning key,
Cassandra doesn't know where to look for that data, and will need to query
all of it to find partitions matching that restriction.

If you want to select distinct you should probably do it in a distributed
manner using token range scans, however this is generally not a good use
case for Cassandra. If you really need to know your partitioning keys you
should probably store them in a separate cache.


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