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https://issues.apache.org/jira/browse/IMPALA-10008?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tim Armstrong updated IMPALA-10008:
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Component/s: Frontend
> 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
> Components: Frontend
> Affects Versions: Impala 3.4.0
> Reporter: Aman Sinha
> Priority: Major
>
> 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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