Hi,
Assuming that 4 tables are small enough to fit in the Distributed Cache, the
joins between the tables all need to join against a common key.
Example:
set hive.auto.convert.join=true;
SELECT *
FROM large
JOIN smalla ON
large.key = smalla.key1
JOIN smallb ON
large.key = smallb.key2
JOIN smallc ON
large.key = smallc.key3
JOIN smalld ON
large.key = smalld.key4;
Having a different join key will push the join off into a different task, as
will the order of the join condition. In this example, large.key was always on
the left side of the join conditions.
Matt Tucker
-----Original Message-----
From: Abhishek [mailto:[email protected]]
Sent: Wednesday, June 13, 2012 11:13 AM
To: [email protected]
Subject: Map side join
Hi all,
How map side join in hive, can be used to join multiple tables(suppose 5
tables).
Regards
Abhishek
Sent from my iPhone
