Aman Sinha created IMPALA-9915:
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Summary: Num distinct values for IS [NOT] NULL predicate should be
2
Key: IMPALA-9915
URL: https://issues.apache.org/jira/browse/IMPALA-9915
Project: IMPALA
Issue Type: Bug
Components: Frontend
Affects Versions: Impala 3.4.0
Reporter: Aman Sinha
Currently, the NDV of all predicates is hardcoded to 3 following the 3-valued
logic (True/False/Unknown). This is done in Predicate.analyzeImpl() method.
For IsNullPredicate which represents IS NULL and IS NOT NULL, strictly speaking
the NDV should be 2 since it should only evaluate to True or False. Fixing this
is more of a technicality and is not too consequential. There are targeted
tests in ExprCardinalityTest that should be updated when this is fixed.
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