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Hive, mail # user - How does hive decide to launch how many map tasks?


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How does hive decide to launch how many map tasks?
Cheng Su 2012-11-16, 06:39
Hi, all

How does hive decide to launch how many map tasks?
I know there are some configs to help hive to decide how many reduce
task to launch?
But how about map tasks?

I thought that number of map tasks equals to the number of the store files.
I have a table now with 2 partitions, and one has 4 files in it, the
other has 2,
when I execute "select count(*) from table", only one map is launched.

How can I increase the number of map tasks to improve the performance?

Thanks.

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Regards,
Cheng Su