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Hive, mail # user - Performance Issues in Hive with S3 and Partitions

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RE: Performance Issues in Hive with S3 and Partitions
Connell, Chuck 2012-07-27, 19:39
What about making your small files bigger, by ZIPping them together? Of course, you have to think about this carefully, so MapReduce can efficiently retrieve the files it needs without unzipping everything every time.

Sent: Friday, July 27, 2012 2:42 PM
Subject: RE: Performance Issues in Hive with S3 and Partitions


I did not see any major improvement in the performance even after setting "Hive.optimize.s3.query=true", although the same was suggested by AWS Team.

My problem is I have too many small files - 3 level of partition, 6500+ files and a single file is < 1 MB.
Now I know Hadoop and HDFS are not meant to deal with lot of small files, but if that is the way to go is there any work around?


From: Jain Richin (Nokia-LC/Boston)
Sent: Tuesday, July 24, 2012 11:49 AM
Subject: RE: Performance Issues in Hive with S3 and Partitions

Hi Igor,

Thanks for the response. Yes I am using EMR.
I will make changes and let you know if that helps.


From: ext Igor Tatarinov [mailto:[EMAIL PROTECTED]]<mailto:[mailto:[EMAIL PROTECTED]]>
Sent: Tuesday, July 24, 2012 12:38 AM
Subject: Re: Performance Issues in Hive with S3 and Partitions

Are you using EMR?
Have you tried  setting

as mentioned in

I haven't tried using that option myself. I am curious if it helps in your scenario. The above page also mentions another fix that's supposed to help with partitioned tables. Optimizing queries with thousands of input files used to take a lot of time. But it looks like that fix is enabled by default now.

Just in case, also check your jvm reuse option. If it's too low, performance will suffer. I had it set to 3 to avoid running out of memory. Using the default value of 20 really helps when reading lots of small files.

On Mon, Jul 23, 2012 at 8:33 PM, <[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>> wrote:

Sorry this is an AWS Hive Specific question.  I have two External Hive tables for my custom logs.

1. flat directory structure on AWS S3, no partition and files in bz2 compressed format (few big files)

2. With 3 level of partitions on AWS S3 (lot of small uncompressed files)

I noticed that my queries on the table with Partition is taking forever to run. The same queries run fine and finish up quickly on table with no partition.
Am I missing something, I suspect this has something to do with the way S3 behaves.

A query example is :

select id, (max(unix_timestamp(ts, "MM/dd/yyyy HH:mm")) - min(unix_timestamp(ts, "MM/dd/yyyy HH:mm")))/(60*60)
from logs
group by id;