Paul Rogers created IMPALA-8033:
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Summary: PlanNode getInputCardinality has two conflicting meanings
Key: IMPALA-8033
URL: https://issues.apache.org/jira/browse/IMPALA-8033
Project: IMPALA
Issue Type: Bug
Components: Frontend
Affects Versions: Impala 3.1.0
Reporter: Paul Rogers
Assignee: Paul Rogers
The use of the method {{PlanNode.getInputCardinality()}} has evolved to have
two slightly different, but conflicting, meanings:
* The actual cardinality of the input table, needed to compute join cardinality.
* The number of rows to be read, taking into consideration any limits placed on
reading.
Because join calculations are wrong if we do not use the actual base table
cardinality, we cannot use the input cardinality interchangeably with table
cardinality.
Instead, break the function into two: {{getTableCardinality()}} to get the
actual cardinality for use in joins, and the existing {{getInputCardinality()}}
used for other purposes.
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