Seonggon Namgung created HIVE-29161:
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Summary: Update statistics correctly when applying the impact of
Dynamic SemiJoin Reduction
Key: HIVE-29161
URL: https://issues.apache.org/jira/browse/HIVE-29161
Project: Hive
Issue Type: Bug
Reporter: Seonggon Namgung
Assignee: Seonggon Namgung
During SemiJoin branch removal based on benefit, Hive temporarily updates the
statistics of the filter operator so that a later-visited SemiJoin branch is
aware of the effect of the surviving SemiJoin branch. The adjusted number of
rows is computed using the following code:
{code:java}
long newNumRows = (long) (1.0 - roi.reductionFactor) *
roi.filterStats.getNumRows(); {code}
Due to the missing parentheses, Hive currently sets newNumRows either to 1
(adjusted from 0) or to the original value. This leads to incorrect decisions
in subsequent SemiJoin benefit computations and may result in suboptimal query
plans.
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