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https://issues.apache.org/jira/browse/HBASE-605?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12599192#action_12599192
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Clint Morgan commented on HBASE-605:
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Nope. A single SortedSet is created/maintained per order-able column. The we'd
like to iterate through it forwards or backwards to respond to the client's
scanner request.
I suppose we could maintain two such Sorted (forwards and backwards) by
inverting the Comparator, but this seems a waste of space and time....
> 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
> Fix For: 0.3.0
>
> 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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