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https://issues.apache.org/jira/browse/CALCITE-1960?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16159015#comment-16159015
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Julian Hyde commented on CALCITE-1960:
--------------------------------------
We need a test that will fail without your fix, succeed with it. It will detect
if (say) someone accidentally reverts your change in future. We can't engineer
a project this scale unless every feature has an automatic test. I hope you can
understand that.
> Duplicated mapping generated from RelMdPredicates
> -------------------------------------------------
>
> Key: CALCITE-1960
> URL: https://issues.apache.org/jira/browse/CALCITE-1960
> Project: Calcite
> Issue Type: Bug
> Components: core
> Reporter: Rheet Wong
> Assignee: Julian Hyde
> Original Estimate: 1h
> Remaining Estimate: 1h
>
> When inferring pulled up predicates, multiple mappings are generated to
> make sure equivalent expressions can be substitute. E.g., for an expression
> 'a + b + c' and the following equivalences:
> {code:sql}
> a : {a, b}
> b : {a, b}
> c : {c, e}
> {code}
> should generate:
> {code:sql}
> a + a + c
> a + a + e
> a + b + c
> a + b + e
> b + a + c
> b + a + e
> b + b + c
> b + b + e
> {code}
> The mapping generation is a typical permutation generation process. However,
> the current code is not handling the permutation well, thus causing
> duplicated
> mappings.
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