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INSERT INTO transaction table, only one reducer task

New Contributor


Could you help me understand why my inserts into transaction table (bucketed, stored as ORC) always involves one last reducer task?

Hive: 3.1.2 , Tez: 0.9 

I mean, hive query plan looks good, it creates appropriate amount of stages / mapper tasks and reducer tasks according to the volume of data but it always has one last reducer with only one task.

I can not understand why it is so and it seems inefficient. I read that if there are multiple buckets, hive is able to write simultaneously to transnational table using multiple reducer tasks.


New Contributor

anyone any thoughts on this?

New Contributor

Could you provide some examples?