hive-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Venky Iyer (JIRA)" <>
Subject [jira] Commented: (HIVE-900) Map-side join failed if there are large number of mappers
Date Sat, 24 Oct 2009 02:52:59 GMT


Venky Iyer commented on HIVE-900:

This is a high-priority bug for me, blocking me on fairly important stuff . The workaround
that Dhruba had, of downloading data to the client and adding to the distributedcache is a
pretty good solution.

> Map-side join failed if there are large number of mappers
> ---------------------------------------------------------
>                 Key: HIVE-900
>                 URL:
>             Project: Hadoop Hive
>          Issue Type: Improvement
>            Reporter: Ning Zhang
>            Assignee: Ning Zhang
> Map-side join is efficient when joining a huge table with a small table so that the mapper
can read the small table into main memory and do join on each mapper. However, if there are
too many mappers generated for the map join, a large number of mappers will simultaneously
send request to read the same block of the small table. Currently Hadoop has a upper limit
of the # of request of a the same block (250?). If that is reached a BlockMissingException
will be thrown. That cause a lot of mappers been killed. Retry won't solve but worsen the

This message is automatically generated by JIRA.
You can reply to this email to add a comment to the issue online.

View raw message