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From "David S. Wang (Work started) (JIRA)" <j...@apache.org>
Subject [jira] [Work started] (HBASE-5489) Add HTable accessor to get regions for a key range
Date Wed, 29 Feb 2012 16:21:57 GMT

     [ https://issues.apache.org/jira/browse/HBASE-5489?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Work on HBASE-5489 started by David S. Wang.

> Add HTable accessor to get regions for a key range
> --------------------------------------------------
>                 Key: HBASE-5489
>                 URL: https://issues.apache.org/jira/browse/HBASE-5489
>             Project: HBase
>          Issue Type: Improvement
>          Components: client
>            Reporter: David S. Wang
>            Assignee: David S. Wang
>            Priority: Minor
> It would be nice to have an accessor to find all regions that overlap with a particular
range of keys. Right now, the only way to accomplish that is to call HTable.getStartEndKeys(),
then follow that with calls to getRegionLocation() for the range of keys you are interested
in.  This algorithm has 2 drawbacks:
> * It returns more keys than is necessary most of the time.  This is especially evident
if there are a lot of regions comprising the table and the range of keys is small.
> * It always does a scan of .META. via MetaScannerVisitor for at least HTable.getStartEndKeys(),
and perhaps for HRegionLocations that are not already cached by the client.
> An accessor that limited its scans to a specified range could avoid scanning .META. at
all if the HRegionLocations being fetched were already cached by the client, thereby potentially
making this operation faster in common cases.
> Here's a proposal for the accessor:
>   /**
>    * Get the corresponding regions for an arbitrary range of keys.
>    * <p>
>    * @param startRow Starting row in range, inclusive
>    * @param endRow Ending row in range, inclusive
>    * @return A list of HRegionLocations corresponding to the regions that
>    * contain the specified range
>    * @throws IOException if a remote or network exception occurs
>    */
>   public List<HRegionLocation> getRegionsInRange(final byte [] startKey,
>     final byte [] endKey) throws IOException

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