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https://issues.apache.org/jira/browse/CASSANDRA-12915?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15897907#comment-15897907
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Alex Petrov commented on CASSANDRA-12915:
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This was a piece of test that remained from your code, the approach I suggest
is slightly different, so I'm not surprised the empty range still counts as a
range.
My point is that we could have even taken out the null check from
[here|https://github.com/ifesdjeen/cassandra/commit/78b1ff630536b0f48787ced74a66d702d13637ba#diff-25d7f486e2818c56d6b01aa952d459f3L146]
and replaced it with an empty iterator and would still achieve the same result
and get the issue fixed.
If you disagree with the approach I'm proposing, you could answer my initial
question and explain. I'm open, I just want to understand before we get it
committed.
> SASI: Index intersection with an empty range really inefficient
> ---------------------------------------------------------------
>
> Key: CASSANDRA-12915
> URL: https://issues.apache.org/jira/browse/CASSANDRA-12915
> Project: Cassandra
> Issue Type: Improvement
> Components: sasi
> Reporter: Corentin Chary
> Assignee: Corentin Chary
> Fix For: 3.11.x, 4.x
>
>
> It looks like RangeIntersectionIterator.java 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.
> * CASSANDRA-10765
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