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From "Karthik Kumara (JIRA)" <>
Subject [jira] [Updated] (HIVE-4247) Filtering on a hbase row key duplicates results across multiple mappers
Date Thu, 28 Mar 2013 20:15:16 GMT


Karthik Kumara updated HIVE-4247:

    Attachment: HiveHBaseTableInputFormat.patch

Suggested patch
> Filtering on a hbase row key duplicates results across multiple mappers
> -----------------------------------------------------------------------
>                 Key: HIVE-4247
>                 URL:
>             Project: Hive
>          Issue Type: Bug
>          Components: HBase Handler
>    Affects Versions: 0.9.0
>         Environment: All Platforms
>            Reporter: Karthik Kumara
>              Labels: patch
>         Attachments: HiveHBaseTableInputFormat.patch
> Steps to reproduce
> 1. Create a Hive external table with HiveHbaseHandler with enough data in the hbase table
to spawn multiple mappers for the hive query.
> 2. Write a query which has a filter (in the where clause) based on the hbase row key.

> 3. Running the map reduce job leads to each mapper querying the entire data set.  duplicating
the data for each mapper. Each mapper processes the entire filtered range and the results
get multiplied as the number of mappers run.
> Expected behavior:
> Each mapper should process a different part of the data and should not duplicate.
> Cause:
> The cause seems to be the convertFilter method in HiveHBaseTableInputFormat. convertFilter
has this piece of code which rewrites the start and the stop row for each split which leads
each mapper to process the entire range
>  if (tableSplit != null) {
>       tableSplit = new TableSplit(
>         tableSplit.getTableName(),
>         startRow,
>         stopRow,
>         tableSplit.getRegionLocation());
>     }
> The scan already has the start and stop row set when the splits are created. So this
piece of code is probably redundant.

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