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https://issues.apache.org/jira/browse/IMPALA-9915?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Aman Sinha updated IMPALA-9915:
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Description: 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 probably
won't affect explain plans in the tests. There are targeted tests in
ExprCardinalityTest that should be updated when this is fixed. (was:
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.)
> 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
> Priority: Minor
>
> 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 probably won't affect explain plans
> in the tests. There are targeted tests in ExprCardinalityTest that should be
> updated when this is fixed.
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