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Date: Fri, 10 Mar 2017 13:07:04 +0000 (UTC)
From: "Alex Petrov (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (CASSANDRA-12915) SASI: Index intersection with
 an empty range really inefficient
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archived-at: Fri, 10 Mar 2017 13:07:30 -0000


    [ https://issues.apache.org/jira/browse/CASSANDRA-12915?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15905037#comment-15905037 ] 

Alex Petrov commented on CASSANDRA-12915:
-----------------------------------------

Committed as [2c111d15bb080283b9b98d48fab4bcf4db515b5a|https://github.com/apache/cassandra/commit/2c111d15bb080283b9b98d48fab4bcf4db515b5a] to 3.11 and merged up to trunk.

A small side note: this was my very first time as I have committed anyone else's code to the repository, and I have accidentally forgotten to include {{--amend}} with author name, so the patch got pushed under my credentials. Since we're a big project we can not really amend the history on primary branches and just force-push. I've included a proper attribution on the authorship in the patch comment, but the github history unfortunately would still hold my email. I'm really sorry about that, I will take an extra care next time. Thank you for understanding,

> 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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