hive-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Navis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-3420) Inefficiency in hbase handler when process query including rowkey range scan
Date Wed, 12 Dec 2012 05:53:21 GMT

    [ https://issues.apache.org/jira/browse/HIVE-3420?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13529641#comment-13529641
] 

Navis commented on HIVE-3420:
-----------------------------

@Gang Deng 
This is pretty important issue. I'll make a patch for a review.
                
> Inefficiency in hbase handler when process query including rowkey range scan
> ----------------------------------------------------------------------------
>
>                 Key: HIVE-3420
>                 URL: https://issues.apache.org/jira/browse/HIVE-3420
>             Project: Hive
>          Issue Type: Improvement
>          Components: HBase Handler
>    Affects Versions: 0.9.0
>         Environment: Hive-0.9.0 + HBase-0.94.1
>            Reporter: Gang Deng
>            Priority: Critical
>   Original Estimate: 2h
>  Remaining Estimate: 2h
>
> When query hive with hbase rowkey range, hive map tasks do not leverage startrow, endrow
information in tablesplit. For example, if the rowkeys fit into 5 hbase files, then where
will be 5 map tasks. Ideally, each task will process 1 file. But in current implementation,
each task processes 5 files repeatedly. The behavior not only waste network bandwidth, but
also worse the lock contention in HBase block cache as each task have to access the same block.
The problem code is in HiveHBaseTableInputFormat.convertFilte as below:
> ……
>     if (tableSplit != null) {
>       tableSplit = new TableSplit(
>         tableSplit.getTableName(),
>         startRow,
>         stopRow,
>         tableSplit.getRegionLocation());
>     }
>     scan.setStartRow(startRow);
>     scan.setStopRow(stopRow);
> ……
> As tableSplit already include startRow, endRow information of file, the better implementation
will be:
>         ……
>         byte[] splitStart = startRow;
>         byte[] splitStop = stopRow;
>     if (tableSplit != null) {
>                 
>            if(tableSplit.getStartRow() != null){
>                         splitStart = startRow.length == 0 ||
>           Bytes.compareTo(tableSplit.getStartRow(), startRow) >= 0 ?
>             tableSplit.getStartRow() : startRow;
>                 }
>                 if(tableSplit.getEndRow() != null){
>                         splitStop = (stopRow.length == 0 ||
>           Bytes.compareTo(tableSplit.getEndRow(), stopRow) <= 0) &&
>           tableSplit.getEndRow().length > 0 ?
>             tableSplit.getEndRow() : stopRow;
>                 }                       
>       tableSplit = new TableSplit(
>         tableSplit.getTableName(),
>         splitStart,
>         splitStop,
>         tableSplit.getRegionLocation());
>     }
>     scan.setStartRow(splitStart);
>     scan.setStopRow(splitStop);
>         ……
> In my test, the changed code will improve performance more than 30%.

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira

Mime
View raw message