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From shashwat shriparv <dwivedishash...@gmail.com>
Subject Re: INSERT OVERWRITE LOCAL DIRECTORY
Date Fri, 14 Feb 2014 10:52:57 GMT
Because when you do select * the query just has to read and return the
resultl but when you give query under query suffle sort and comparison
happens thats why mapreduce...


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On Fri, Feb 14, 2014 at 4:15 PM, Nitin Pawar <nitinpawar432@gmail.com>wrote:

> when you are writing a file, it will need an application to create and
> write the file.
> Thats why the mapreduce job to create the file.
>
> Where as for other way when its displayed on console, its just hdfs cat
> operation
>
>
> On Fri, Feb 14, 2014 at 4:13 PM, Sreenath <sreenaths1923@gmail.com> wrote:
>
>> i have two queries
>> 1. select * from  tab1 limit 3;
>> this returns the 3 rows quickly withoput launcing any map reduce jobs;
>>
>> 2. INSERT OVERWRITE LOCAL DIRECTORY "/tmp/query1/" select * from tab1
>> limit 3;
>> but the same above query to write to a local directory launches a map
>> reduce job and scans through all the rows launching map-reduce jobs
>>
>> why the differenceinexecution of both queries?
>>
>> --
>> Sreenath S Kamath
>> Bangalore
>> Ph No:+91-9590989106
>>
>
>
>
> --
> Nitin Pawar
>

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