user1189851 user1189851 - 1 month ago 23
SQL Question

ROW_NUMBER( ) OVER in impala

I have a use case where I need to use ROW_NUMBER() over PARTITION:
Something like:

SELECT
Column1 , Column 2
ROW_NUMBER() OVER (
PARTITION BY ACCOUNT_NUM
ORDER BY FREQ, MAN, MODEL) as LEVEL
FROM
TEST_TABLE


I need a workaround for this in Impala. Unfortunately Impala does not support sub queries and also does not support ROW_NUMBER() OVER functionality.
Thank you for your help.

Answer

Impala is rather limited for this type of query. With some assumptions, this query is possible:

  • The four columns in the partitioning clause are never NULL
  • The four columns in the partitioning clause uniquely identify a row

The query is rather ugly and expensive:

select tt.column1, tt.column2, count(*) as level
from test_table tt join
     test_table tt2
     on tt.account_num = tt2.account_num and
        (tt2.freq < tt.freq or
         tt2.freq = tt.freq and tt2.man < t.man or
         tt2.freq = tt.freq and tt2.man = t.man and tt2.model <= t.model
        )
group by tt.column1, tt.column2, tt.account_num, tt.freq, tt.man, tt.model;