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From "Alex Liu (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-6048) CQL3 data filtering improvement
Date Tue, 17 Sep 2013 22:05:52 GMT
Alex Liu created CASSANDRA-6048:
-----------------------------------

             Summary: CQL3 data filtering improvement
                 Key: CASSANDRA-6048
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6048
             Project: Cassandra
          Issue Type: Bug
          Components: Core
            Reporter: Alex Liu


Existing data filtering uses the following algorithm

{code}
   1. find best selective predicate based on the smallest mean columns count
   2. fetch rows for the best selective predicate predicate, then filter the data based on
other predicates left.
{code}

So potentially we could improve the performance by

{code}
   1.  joining multiple predicates then do the data filtering for other predicates.
   2.  fine tune the best predicate selection algorithm
{code}

For multiple predicate join, it could improve performance if one predicate has many entries
and another predicate has a very few of entries. It means a few index CF read, join the row
keys, fetch rows then filter other predicates.

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