Paul Rogers created IMPALA-8022:
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Summary: Add cardinality checks to PlannerTest
Key: IMPALA-8022
URL: https://issues.apache.org/jira/browse/IMPALA-8022
Project: IMPALA
Issue Type: Improvement
Components: Frontend
Affects Versions: Impala 3.1.0
Reporter: Paul Rogers
Assignee: Paul Rogers
IMPALA-8021 suggests that we add cardinality to the standard EXPLAIN output.
When we do so, the cardinality will appear in the plans generated by
{{PlannerTest}}. We could just ignore the numbers, as we do for other derived
values. Or, we could use this opportunity to verify the expected cardinalities.
The expected cardinality is a critical number when planning queries: we decide
join planning based on that number (sometimes multiplied by row width.) To
prevent regressions, we want to verify that we've not changed the cardinality
estimates except by design.
Since cardinality estimates may vary a bit, do a range-based comparison,
accepting as valid any value within 5% of the expected value. (Except for zero,
if zero is expected, the actual estimate must also be zero.)
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