-Re: Compression of Intermediate Data
Bejoy KS 2012-10-06, 15:32
The propertis you specified doen't enable compression of map output. To enable map output compression you need to enable the following properties
This property 'hive.exec.compress.intermediate
' Is used to enable compression of data in between multiple mapreduce jobs generated by a hive query.
Sent from handheld, please excuse typos.
From: Hadi Moshayedi <[EMAIL PROTECTED]>
Date: Sat, 6 Oct 2012 16:55:47
To: <[EMAIL PROTECTED]>
Reply-To: [EMAIL PROTECTED]
Subject: Compression of Intermediate Data
I wanted to look into improving performance of my Hive cluster, and from
what I read turning on compression of intermediate data could help. As I
understand, this would help because it would reduce the amount of data
written to disk in between jobs.
I look at the documentation and set the following settings:
I ran some queries to see how compression impacts the performance. But it
usually made the query time worse. I also had a query whose size of
intermediate data was close to the size of input data, but it made the
performance worse for this query too.
Question 1: Are the above settings correct settings for using compression
of intermediate data?
Question 2: Are there use-cases in which compression of intermediate data
would not help performance? Why would someone not keep it turned on always?