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From "Benedict (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-6933) Optimise Read Comparison Costs in collectTimeOrderedData
Date Thu, 10 Apr 2014 12:47:16 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-6933?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Benedict updated CASSANDRA-6933:
--------------------------------

    Attachment: 6933.v5fix.txt

Just realised: we were all so busy dissecting the extra binary search that we missed a bug
with the initial ordered comparison. If the next name queried is *less* than the next name
in the ABSC, we will still increment our counter past the next name (when we should leave
it where it is).

Attached a super simple diff that fixes this.

> Optimise Read Comparison Costs in collectTimeOrderedData
> --------------------------------------------------------
>
>                 Key: CASSANDRA-6933
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6933
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Benedict
>            Assignee: Benedict
>            Priority: Minor
>              Labels: performance
>             Fix For: 3.0
>
>         Attachments: 6933-v3.txt, 6933-v4.txt, 6933-v5.txt, 6933.v5fix.txt
>
>
> Introduce a new SearchIterator construct, which can be obtained from a ColumnFamily,
which permits efficiently iterating a subset of the cells in ascending order. Essentially,
it saves the previously visited position and searches from there, but also tries to avoid
searching the whole remaining space if possible.



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