Home | About | Sematext search-lucene.com search-hadoop.com
 Search Hadoop and all its subprojects:

Switch to Threaded View
Hive >> mail # user >> most efficient way to concatenate 3 tables into one?


Copy link to this message
-
Re: most efficient way to concatenate 3 tables into one?
Then you will get a copy of each sub table.
My project use external partitions instead, and in this way, you don't
need to cp sub tables.
1) Create a table some_table
2) ALTER TABLE some_table ADD PARTITION (partition_col 'partition_col_value1') LOCATION '/user/data/subTable1'
ALTER TABLE some_table ADD PARTITION (partition_col 'partition_col_value2') LOCATION '/user/data/subTable2'

On Thu, Sep 13, 2012 at 4:23 AM, Bejoy KS <[EMAIL PROTECTED]> wrote:
> Hi
>
> Just follow the steps
> 1) Create an external table with location as /user/aggregatedTable
> 2) Move the contents of 3 monthly tables to this location
> Hadoop fs -cp /user/monthlyTable1/* /user/aggregatedTable
>
> Hadoop fs -cp /user/monthlyTable2/* /user/aggregatedTable
>
> ...
>
> Replace the hsfs dirs in the above commands with those used in your tables.
> Regards
> Bejoy KS
>
> Sent from handheld, please excuse typos.
> ________________________________
> From: zuohua zhang <[EMAIL PROTECTED]>
> Date: Wed, 12 Sep 2012 13:14:20 -0700
> To: <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>
> ReplyTo: [EMAIL PROTECTED]
> Subject: Re: most efficient way to concatenate 3 tables into one?
>
> Thanks Bejoy.
> Yes, they have the same schema.
> Can you explain further how to? I am new to hive.
>
>
> On Wed, Sep 12, 2012 at 1:06 PM, Bejoy KS <[EMAIL PROTECTED]> wrote:
>>
>> Hi
>>
>> If all the 3 tables have the same. Schema, Create an external table and
>> move the data from all the 3 tables to this new table's location. Just a
>> hdfs copy or move is not that expensive.
>> Regards
>> Bejoy KS
>>
>> Sent from handheld, please excuse typos.
>> ________________________________
>> From: zuohua zhang <[EMAIL PROTECTED]>
>> Date: Wed, 12 Sep 2012 13:02:42 -0700
>> To: <[EMAIL PROTECTED]>
>> ReplyTo: [EMAIL PROTECTED]
>> Subject: most efficient way to concatenate 3 tables into one?
>>
>> I have 3 tables, each contains monthly data, I would like to make a table
>> to concatenate all 3 months into 1 table.
>> What is the most efficient way to do that?
>> I am using insert into which takes a long time.
>>
>> Thanks!
>
>