If any of the 100 rows that the sub-query returns do not satisfy the where clause, there would be no rows in the overall result. Do we still consider that the Hive query is verified in this case?
Regards, Ramki. On Wed, Mar 6, 2013 at 1:14 AM, Dean Wampler < dean.wamp...@thinkbiganalytics.com> wrote: > NIce, yea that would do it. > > > On Tue, Mar 5, 2013 at 1:26 PM, Mark Grover > <grover.markgro...@gmail.com>wrote: > >> I typically change my query to query from a limited version of the whole >> table. >> >> Change >> >> select really_expensive_select_clause >> from >> really_big_table >> where >> something=something >> group by something=something >> >> to >> >> select really_expensive_select_clause >> from >> ( >> select >> * >> from >> really_big_table >> limit 100 >> )t >> where >> something=something >> group by something=something >> >> >> On Tue, Mar 5, 2013 at 10:57 AM, Dean Wampler >> <dean.wamp...@thinkbiganalytics.com> wrote: >> > Unfortunately, it will still go through the whole thing, then just >> limit the >> > output. However, there's a flag that I think only works in more recent >> Hive >> > releases: >> > >> > set hive.limit.optimize.enable=true >> > >> > This is supposed to apply limiting earlier in the data stream, so it >> will >> > give different results that limiting just the output. >> > >> > Like Chuck said, you might consider sampling, but unless your table is >> > organized into buckets, you'll at least scan the whole table, but maybe >> not >> > do all computation over it ?? >> > >> > Also, if you have a small sample data set: >> > >> > set hive.exec.mode.local.auto=true >> > >> > will cause Hive to bypass the Job and Task Trackers, calling APIs >> directly, >> > when it can do the whole thing in a single process. Not "lightning >> fast", >> > but faster. >> > >> > dean >> > >> > On Tue, Mar 5, 2013 at 12:48 PM, Joey D'Antoni <jdant...@yahoo.com> >> wrote: >> >> >> >> Just add a limit 1 to the end of your query. >> >> >> >> >> >> >> >> >> >> On Mar 5, 2013, at 1:45 PM, Kyle B <kbi...@gmail.com> wrote: >> >> >> >> Hello, >> >> >> >> I was wondering if there is a way to quick-verify a Hive query before >> it >> >> is run against a big dataset? The tables I am querying against have >> millions >> >> of records, and I'd like to verify my Hive query before I run it >> against all >> >> records. >> >> >> >> Is there a way to test the query against a small subset of the data, >> >> without going into full MapReduce? As silly as this sounds, is there a >> way >> >> to MapReduce without the overhead of MapReduce? That way I can check my >> >> query is doing what I want before I run it against all records. >> >> >> >> Thanks, >> >> >> >> -Kyle >> > >> > >> > >> > >> > -- >> > Dean Wampler, Ph.D. >> > thinkbiganalytics.com >> > +1-312-339-1330 >> > >> > > > > -- > *Dean Wampler, Ph.D.* > thinkbiganalytics.com > +1-312-339-1330 > >
