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  1. Kudu
  2. KUDU-1880

IS NULL predicates eliminate some NULL values

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    Details

    • Type: Bug
    • Status: Resolved
    • Priority: Blocker
    • Resolution: Fixed
    • Affects Version/s: 1.3.0
    • Fix Version/s: 1.3.0
    • Component/s: None
    • Labels:
      None
    • Target Version/s:

      Description

      Impala is implementing IS NULL/IS NOT NULL Kudu predicates as part of IMPALA-4859 (see review: https://gerrit.cloudera.org/#/c/5958/ ). In testing, Kudu IS NULL is eliminating valid NULL values from results returned.

      Here is an example:
      select id, float_col from functional_kudu.alltypesagg where id < 10;

      id float_col
      3 3.299999952316284
      7 7.699999809265137
      0 NULL
      6 6.599999904632568
      8 8.800000190734863
      9 9.899999618530273
      0 NULL
      1 1.100000023841858
      2 2.200000047683716
      4 4.400000095367432
      5 5.5

      Fetched 11 row(s) in 0.57s

      When adding an IS NULL condition on float_col, this does not return any rows.
      select id, float_col from functional_kudu.alltypesagg where id < 10 and float_col is null;
      Fetched 0 row(s) in 0.25s

      This is also true for other tables, such as functional_kudu.nulltable.

      select * from functional_kudu.nulltable;

      a b c d e f g
      a   NULL NULL NULL ab  

      Fetched 1 row(s) in 0.49s

      The following SQLs return no rows:
      select * from functional_kudu.nulltable where c is null;
      select * from functional_kudu.nulltable where d is null;
      select * from functional_kudu.nulltable where e is null;

      Impala statistics indicate that Kudu is not returning any rows. IS NOT NULL seems to work correctly.

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            • Assignee:
              andrew.wong Andrew Wong
              Reporter:
              joemcdonnell Joe McDonnell
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              Dates

              • Created:
                Updated:
                Resolved: