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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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Julian Hyde resolved CALCITE-4351.
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Fix Version/s: 1.33.0
Resolution: Fixed
Fixed in
[90546821|https://github.com/apache/calcite/commit/9054682145727fbf8a13e3c79b3512be41574349].
Thanks for an excellent fix, [~fan_li_ya]!
> RelMdUtil#numDistinctVals always returns 0 for large inputs
> -----------------------------------------------------------
>
> 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
> Labels: pull-request-available
> Fix For: 1.33.0
>
> Time Spent: 20m
> Remaining Estimate: 0h
>
> 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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