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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CASSANDRA-350) optimize away unnecessary range scans
Date Tue, 27 Oct 2009 21:16:59 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-350?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12770646#action_12770646
] 

Jonathan Ellis commented on CASSANDRA-350:
------------------------------------------

well, there's two bail out cases

the first is "the index tells us there can't possibly be data we're looking for here" and
that should work fine w/ reversed

the second is "i've scanned some data in a block and I know I can stop scanning early b/c
I reached finished" and you're right, that one can't be done w/ reversed

> optimize away unnecessary range scans
> -------------------------------------
>
>                 Key: CASSANDRA-350
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-350
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Jonathan Ellis
>            Assignee: Gary Dusbabek
>             Fix For: 0.5
>
>         Attachments: cassandra-350-v2-tests.patch, cassandra-350-v2.patch, cassandra-350.patch
>
>
> Even when a the columns exist for a given key, they usually won't exist in all the sstable
segments.  So avoiding the scan when the column index shows we can, will be a win.
> This is what the todo in SSTableSliceIterator is about:
>         // TODO push finishColumn down here too, so we can tell when we're done and optimize
away the slice when the index + start/stop shows there's nothing to scan for

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