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  1. Hive
  2. HIVE-21074

Hive bucketed table query pruning does not work for IS NOT NULL condition

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      The current version of bucket pruning skips all the predicates when it detects that one of the predicates is a compound type (e.g. NOT(IS_NULL) ) when evaluating AND logical operators.

      This logic is faulty since as long as one of the AND operators is a bucketed column (col = literal), the literal value of that col should be considered in the bucket pruning optimization no matter what. For example:

      SELECT * FROM tbl WHERE bucketed_col = 1 AND (some_compound_expr)

      Then the the value '1' should be considered for pruning in the query plan. This limitation has manifested into a simpler case where a table that I am trying to optimized using bucketing technique is not effective when IS NOT NULL is used. Since IS NOT NULL is parsed into NOT(IS_NULL) (a compound expression), the pruning phase is completed skipped causing unnecessary tasks to be spawned. For instance:

      SELECT * FROM tbl WHERE bucketed_col = 1 AND some_other_col IS NOT NULL

      Will not trigger bucket pruning logic and perform a full table scan.

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        1. HIVE-21074.patch
          6 kB
          Thai Bui

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            szita Ádám Szita Assign to me
            thaibui Thai Bui
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