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https://issues.apache.org/jira/browse/CASSANDRA-6048?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13770171#comment-13770171
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Alex Liu commented on CASSANDRA-6048:
-------------------------------------
Add "ALLOW FILTERING JOIN" to CQL clause. By default, it's not using join
filtering, so end user can decide when to use join filtering by specify "ALLOW
JOIN FILTERING".
> CQL3 data filtering improvement
> -------------------------------
>
> Key: CASSANDRA-6048
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6048
> Project: Cassandra
> Issue Type: Improvement
> 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
> Another approach is to have index on multiple columns.
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