George Pachitariu created HIVE-20262:
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Summary: Implement stats annotation rule for the UDTFOperator
Key: HIVE-20262
URL: https://issues.apache.org/jira/browse/HIVE-20262
Project: Hive
Issue Type: Improvement
Components: Physical Optimizer
Reporter: George Pachitariu
Assignee: George Pachitariu
User Defined Table Functions (UDTFs) change the number of rows of the output. A
common UDTF is the explode() method that creates a row for each element for
each array in the input column.
Right now, the number of output rows is equal to the number of input rows. But
if the average number of output rows is bigger than 1, the resulting number of
rows is underestimated in the execution plan.
Implement a rule that can have a factor X as a parameter and for each UDTF
function predict that:
{code:java}
number of output rows = X * number of input rows{code}
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