Why do you think the current generated code is inefficient?


From: John Omernik [mailto:j...@omernik.com]
Sent: Tuesday, September 25, 2012 2:57 PM
To: user@hive.apache.org
Subject: Hive File Sizes, Merging, and Splits

I am really struggling trying to make hears or tails out of how to optimize the 
data in my tables for best query times.  I have a partition that is compressed 
(Gzip) RCFile data in two files

total 421877
263715 -rwxr-xr-x 1 darkness darkness 270044140 2012-09-25 13:32 000000_0
158162 -rwxr-xr-x 1 darkness darkness 161956948 2012-09-25 13:32 000001_0



No matter what I set my split settings to prior to the job, I always get three 
mappers.  My block size is 268435456 but the setting doesn't seem to change 
anything. I can set split size huge or small with no apparent affect on the 
data.


I know there are many esoteric items here, but is there any good documentation 
on setting these things to make my queries on this data more efficient. I am 
not sure what it needs three map tasks on this data, it should really just grab 
two mappers. Not to mention, I thought gzip wasn't splitable anyhow.  So, from 
that standpoint, how does it even send data to three mappers.  If you know of 
some secret cache of documentation for hive, I'd love to read it.

Thanks

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