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From P Reeder <p_ree...@persistentsys.com>
Subject aliases for histogram_numeric (a UDTF)
Date Tue, 05 Nov 2013 22:21:29 GMT
I'm trying to use histogram_numeric(), and output the results as a table with an x and y column,
one row per bin.

SELECT histogram_numeric(freight, 10) from flights
produces an array of JSON objects:
[{"x":25702.200152788293,"y":79849},{"x":2287471.0415704413,"y":866},{"x":5190680.02686567,"y":335},{"x":8346807.222222222,"y":18},{"x":10504284.416666666,"y":12},{"x":12534902.199999997,"y":15},{"x":17483294.5,"y":4},{"x":20163190,"y":1},{"x":27849459,"y":2},{"x":30078666,"y":1}]

select explode(histogram_numeric(freight, 10)) as foo from flights
produces ten rows of JSON objects:
{"x":25702.200152788293,"y":79849}

{"x":2287471.0415704413,"y":866}

{"x":5190680.02686567,"y":335}
...



select inline(histogram_numeric(freight, 10)) as foo from flights
gets the error "FAILED: SemanticException [Error 10083]: The number of aliases supplied in
the AS clause does not match the number of columns output by the UDTF expected 2 aliases but
got 1"
which is not unreasonable, since there should be two columns of output

However
select inline(histogram_numeric(freight, 10)) as foo,bar from flights
gets the error "FAILED: SemanticException 1:53 Only a single expression in the SELECT clause
is supported with UDTF's. Error encountered near token 'bar'"

and
select inline(histogram_numeric(freight, 10)) as [foo,bar] from flights
gets the error "FAILED: ParseException line 1:46 mismatched input 'as' expecting FROM near
')' in from clause"

and
select inline(histogram_numeric(freight, 10)) as (foo,bar) from flights
gets the error "java.lang.Exception: Total MapReduce CPU Time Spent: 6 seconds 30 msec: Job
0: Map: 1 Reduce: 1 Cumulative CPU: 6.03 sec HDFS Read: 17108227 HDFS Write: 0 FAIL"


Is there a syntax to do this, or do I need to use LATERAL VIEW syntax? (If so, is there a
clearer explanation of LATERAL VIEW than https://cwiki.apache.org/confluence/display/Hive/LanguageManual+LateralView
 ?)

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