Hello,
We are on hive 0.11. We have used hive-hbase handler to read / write
data from hbase.
We have query like
Select *
from a
join ext_b b ON a.x = b.y
join ext_c c ON a.p = c.p
One of the join tables (ext_c) is small and we wanted it to be
converted to map join. However, we observed that every external table is
getting converted to a hashtable, maybe due to the estimation of table size
is not right as data is not on hdfs.
Here are the settings. We have
SET hive.auto.convert.join=true;
SET hive.auto.convert.join.noconditionaltask=true;
We tried mapjoin hints as well. Explain shows that map red local task is
present for all and the fall back for that.
Could someone share some pointers/classes/docs on exact workings on when
a table is converted to map join for external tables, it would be helpful.
We would like to understand when a external table qualifies as a small
table eligible for map join.
Please do let me know in case any more details have to be shared.
Regards,
Abhilash L L
Capillary Technologies
M:919886208262
[email protected] | www.capillarytech.com
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