[jira] [Created] (IMPALA-10008) Optimize planning and code generation to leverage non-nullable slots

["Aman Sinha (Jira)" <ji...@apache.org>]

Aman Sinha created IMPALA-10008:
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             Summary: Optimize planning and code generation to leverage non-nullable slots
                 Key: IMPALA-10008
                 URL: https://issues.apache.org/jira/browse/IMPALA-10008
             Project: IMPALA
          Issue Type: Improvement
    Affects Versions: Impala 3.4.0
            Reporter: Aman Sinha


The nullability property of a column/slot should be leveraged to improve both planning and code generation.  During planning, a few different optimizations could be done.  One example is: for predicates like  'a1 IS NOT DISTINCT FROM a2',  if both a1 and a2 are non-nullable, then this predicate can be converted to an equality predicate.   During runtime, this will avoid extra null checks in the hash join's build and probe side which would normally have been done on the presumption that the data could have nulls.  The generated code has null checks in various places (for any SlotRef expr) which could be simplified and hence reduce overhead.

In general, the propagation of nullability property in the plan would make processing of other predicates ( IS NULL, IS NOT NULL) and expressions (e.g NULLIF) much more efficient.




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