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From "Mich Talebzadeh" <m...@peridale.co.uk>
Subject RE: ORC format
Date Mon, 01 Feb 2016 15:49:13 GMT
Use orcfiledump to see the stats for each column etc

 

Example

 

hive --orcfiledump --rowindex 1,2 /user/hive/warehouse/oraclehadoop.db/orctest/000000_0

 

 

Dr Mich Talebzadeh

 

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From: Philip Lee [mailto:philjjoon@gmail.com] 
Sent: 01 February 2016 15:27
To: user@hive.apache.org
Subject: Re: ORC format

 

Also,  

when making ORC from CSV, 

for indexing every key on each coulmn is made, or a primary on a table is made ?

 

If keys are made on each column in a table, accessing any column in some functions like filtering
should be faster.

 

On Mon, Feb 1, 2016 at 4:21 PM, Philip Lee <philjjoon@gmail.com <mailto:philjjoon@gmail.com>
> wrote:

Hello,

 

I experiment the performance of some systems between ORC and CSV file.

I read about ORC documentation on Hive website, but still curious of some things.

 

I know ORC format is faster on filtering or reading because it has indexing.

Has it advantage of joining two tables of ORC dataset as well?

 

Could you explain about it in detail?

When experimenting, it seems like it has some advantages of joining in some aspect, but not
quite sure what characteristic of ORC make this happening rather than CSV.

 

Best,

Phil

 





 

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