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From "Corentin Chary (JIRA)" <>
Subject [jira] [Created] (CASSANDRA-12915) SASI: Index intersection can be very inefficient
Date Wed, 16 Nov 2016 07:50:58 GMT
Corentin Chary created CASSANDRA-12915:

             Summary: SASI: Index intersection can be very inefficient
                 Key: CASSANDRA-12915
             Project: Cassandra
          Issue Type: Bug
          Components: sasi
            Reporter: Corentin Chary

It looks like and be pretty inefficient in some cases. Let's
take the following query:

SELECT data FROM table WHERE index1 = 'foo' AND index2 = 'bar';

In this case:
* index1 = 'foo' will match 2 items
* index2 = 'bar' will match ~300k items

On my setup, the query will take ~1 sec, most of the time being spent in disk.TokenTree.getTokenAt().

if I patch RangeIntersectionIterator so that it doesn't try to do the intersection (and effectively
only use 'index1') the query will run in a few tenth of milliseconds.

I see multiple solutions for that:
* Add a static thresold to avoid the use of the index for the intersection when we know it
will be slow. Probably when the range size factor is very small and the range size is big.

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