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https://issues.apache.org/jira/browse/CASSANDRA-350?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12770638#action_12770638
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Gary Dusbabek commented on CASSANDRA-350:
-----------------------------------------
After working up some test cases and examining the code more closely, it
appears that we can't optimize the case where reversed==true, since it starts
reading at the last block anyway, and when it gets to the first block, it must
start at the beginning to find finishColumn.
Am I seeing things correctly?
> 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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