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From Cam Bazz <>
Subject why some queries produce blank files
Date Fri, 11 Feb 2011 08:51:23 GMT

The query below produces a blank file, when no results are found:

insert overwrite table selection_hourly_clicks partition (date_hour = PARTNAME)
select sel_sid, count(*) cc from (
select split(parse_url(iv.referrer_url,'PATH'), '_')[1] sel_sid from
item_raw iv where iv.date_hour='PARTNAME' AND iv.referrer_url is not
null AND substring(parse_url(iv.referrer_url,'PATH'),0,8)=='/target/'
) s group by sel_sid;

where the following query:

insert overwrite table item_hourly_stat partition (date_hour=PARTNAME)
select iv.e_sid, count(*) from item_raw iv where
iv.date_hour='PARTHANE' group by iv.e_sid";

does not produce a blank file when there is no log at that given hour...

this is not a problem or anything, but i am just trying to understand
what is going on. I am sure it is because the first query in question
is a inner query, or something like that.

best regards,

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