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From "Clint Morgan (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-605) allow scanners which return results ordred by a column value
Date Thu, 22 May 2008 20:45:55 GMT

    [ https://issues.apache.org/jira/browse/HBASE-605?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12599181#action_12599181
] 

Clint Morgan commented on HBASE-605:
------------------------------------

Unfortunately I need the NavigableSet to get a descending iterator. SortedSet does not provide
this functionality. Could use some 3rd party data structure but, ...

I don't get the IOException compile error, thats a java6 change too...

For the time being, I'm inclined to just leave this as a java6 patch and wait until java6
adoption to apply it. Works for me now, and I need to spend time on other things.


> allow scanners which return results ordred by a column value
> ------------------------------------------------------------
>
>                 Key: HBASE-605
>                 URL: https://issues.apache.org/jira/browse/HBASE-605
>             Project: Hadoop HBase
>          Issue Type: New Feature
>          Components: client, regionserver
>    Affects Versions: 0.2.0
>            Reporter: Clint Morgan
>            Priority: Minor
>         Attachments: hbase-605-v2.patch, hbase-605-v3.patch, hbase-605.patch
>
>
> We would like to be able to scan though tables with results ordered by (deserialized)
column values. This approach maintains an in-memory sorted set for each ordered-by column
in each HStore. This allows us to iterate through the keys in column order, and to random
reads on the key to get the full row.
> Without the index, then we have to scan through all the rows to get the first result
ordered by a column. Thus, when R is the number of rows in a table,  N is the number of ordered-by
rows we want, and R >> N we can save a lot of work by not doing the full table scan.

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