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Hive, mail # user - Map side join


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Souvik Banerjee 2012-12-07, 19:58
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Re: Map side join
bejoy_ks@... 2012-12-07, 20:10
Hi Souvik

In earlier versions of hive you had to give the map join hint. But in later versions just set hive.auto.convert.join = true;
Hive automatically selects the smaller table. It is better to give the smaller table as the first  one in join.

You can use a map join if you are joining a small table with a large one, in terms of data size. By small, better to have the smaller table size in range of MBs.

Regards
Bejoy KS

Sent from remote device, Please excuse typos

-----Original Message-----
From: Souvik Banerjee <[EMAIL PROTECTED]>
Date: Fri, 7 Dec 2012 13:58:25
To: <[EMAIL PROTECTED]>
Reply-To: [EMAIL PROTECTED]
Subject: Map side join

Hello everybody,

I have got a question. I didn't came across any post which says somethign
about this.
I have got two tables. Lets say A and B.
I want to join A & B in HIVE. I am currently using HIVE 0.9 version.
The join would be on few columns. like on (A.id1 = B.id1) AND (A.id2 B.id2) AND (A.id3 = B.id3)

Can I ask HIVE to use map side join in this scenario? Should I give a hint
to HIVE by saying /*+mapjoin(B)*/

Get back to me if you want any more information in this regard.

Thanks and regards,
Souvik.

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Souvik Banerjee 2012-12-07, 20:32
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Souvik Banerjee 2012-12-11, 23:12
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bejoy_ks@... 2012-12-12, 14:04
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Souvik Banerjee 2012-12-12, 20:27
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bejoy_ks@... 2012-12-13, 17:12
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Souvik Banerjee 2012-12-13, 18:00
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bejoy_ks@... 2012-12-13, 18:06
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Souvik Banerjee 2012-12-13, 18:36
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Souvik Banerjee 2012-12-27, 23:05