Mehant Baid created DRILL-3429:
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Summary: DrillAvgVarianceConvertlet may produce wrong results
while rewriting stddev, variance
Key: DRILL-3429
URL: https://issues.apache.org/jira/browse/DRILL-3429
Project: Apache Drill
Issue Type: Bug
Reporter: Mehant Baid
Assignee: Mehant Baid
Fix For: 1.2.0
DrillAvgVarianceConvertlet currently rewrites aggregate functions like avg,
stddev, variance to simple computations.
Eg:
Stddev(x) => power(
(sum(x * x) - sum(x) * sum(x) / count(x))
/ count(x),
.5)
Consider the case when the input is an integer. Now the rewrite contains
multiplication and division, which will bind to functions that operate on
integers however the expected result should be a double and since double has
more precision than integer we should be operating on double during the
multiplication and division.
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