I am +1 to adding such functions to Hive, opened a JIRA at:
https://issues.apache.org/jira/browse/HIVE-896
There is no straightforward way right now AFAIK. You can simulate the
LAG function using a map transform, just buffer the last n rows that you
care about in memory as a sliding window, it will only be a local LAG,
won't work across mappers (should be ok if your table is clustered
properly). If you want to do global windowing then you would need to do
that on the reduce side, but it might lead to really bad performance if
you don't set the number of reducers properly.
More on transforms at:
http://wiki.apache.org/hadoop/Hive/LanguageManual/Transform
-- amr
Bosio Andrea wrote:
Hello,
I'm trying to convert some Oracle queries to HIVE.
I have some queries using LEAD and LAG analytic functions (see:
http://ss64.com/ora/syntax-analytic-lead.html)
These functions give access to values in a row prior or after current
position.
Is there a way to do similar things with HIVE?
Thanks.
/--///
/Andrea Bosio// /
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