Hi, when I use Multi Table/File Inserts commands, some may be not more
effective than run table insert commands separately.
For example,
from pokes
insert overwrite table pokes_count
select bar,count(foo) group by bar
insert overwrite table pokes_sum
select bar,sum(foo) group by bar;
To execute this, 2 map/reduce jobs is needed, which is not less than run the
two command separately:
insert overwrite table pokes_count select bar,count(foo) from pokes
group by bar;
insert overwrite table pokes_sum select bar,sum(foo) from pokes group by
bar;
And the time taken is the same.
But the first one seems only scan the table 'pokes' once, why still need 2
map/reduce jobs? And why the time taken couldnot be less?
Is there any way to make it more effective?
Thanks a lot,
Zhou
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