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https://issues.apache.org/jira/browse/CALCITE-4351?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Caizhi Weng updated CALCITE-4351:
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Summary: The result of RelMdUtil#numDistinctVals will always be 0 when
inputs are large (was: The result of RelMdUtil#numDistinctVals is incorrect
when inputs are large)
> The result of RelMdUtil#numDistinctVals will always be 0 when inputs are large
> ------------------------------------------------------------------------------
>
> Key: CALCITE-4351
> URL: https://issues.apache.org/jira/browse/CALCITE-4351
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.26.0
> Reporter: Caizhi Weng
> Priority: Major
>
> Previous implementation of {{RelMdUtil#numDistinctVals}} uses the
> approximation {{ln(1 + x) ~= x}} when {{x}} is small.
> However CALCITE-4132 remove this approximation to make the result more
> accurate. This causes the function to calculate an incorrect result for large
> inputs (for example, when {{domainSize = 1e18}} and {{numSelected = 1e10}}
> the result is 0) due to precision problems.
> What I would suggest is to treat small and large inputs in different ways.
> For small inputs we use the new, more precise function and for large inputs
> we use the old, approximated function.
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