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https://issues.apache.org/jira/browse/CALCITE-2790?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Kevin Risden closed CALCITE-2790.
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> AggregateJoinTransposeRule incorrectly pushes down distinct count into join
> ---------------------------------------------------------------------------
>
> Key: CALCITE-2790
> URL: https://issues.apache.org/jira/browse/CALCITE-2790
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.18.0
> Reporter: Andrew Tsvelodub
> Assignee: Julian Hyde
> Priority: Major
> Fix For: 1.19.0
>
>
> AggregateJoinTransposeRule.EXTENDED can push down aggregate functions into
> the join.
> For Distinct Count (and other distinct aggregate functions) this should not
> be performed the same way as for simple count, since distinct count is not a
> decomposable function. [1]
> While this can be done in theory, by adding the distinct column to the list
> of groups in below aggregate[2], I want to fix the buggy behavior first,
> before trying to improve the existing rule.
> [1] Dynamic Programming: The Next Step, M. Eich, G. Moerkotte
> ([https://ub-madoc.bib.uni-mannheim.de/37228/1/main.pdf])
> [2] Including Group-By in Query Optimization, S. Chaudhuri, K. Shim
> ([https://pdfs.semanticscholar.org/3079/5447cec18753254edbbd7839f0afa58b2a39.pdf])
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