[jira] [Resolved] (CALCITE-1488) ValuesReduceRule should ignore empty Values

["Julian Hyde (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CALCITE-1488?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Julian Hyde resolved CALCITE-1488.
----------------------------------
       Resolution: Fixed
    Fix Version/s: 1.11.0

[~gian], Your analysis of the problem is correct, and your proposed fix would have worked. However, since we already have rules for "propagating emptiness" (in {{PruneEmptyRules}}), the simplest thing is to have {{ValuesReduceRule}} back off and let those rules do their job. (After all, if you have a filter or project on top of an empty relation, it's a waste of effort to simplify the filter or project, because you know the result is going to be empty.) So that's what I have done.

Fixed in http://git-wip-us.apache.org/repos/asf/calcite/commit/f36584ab.

You will need to enable {{PruneEmptyRules.PROJECT_INSTANCE}}, if you haven't already. 

> ValuesReduceRule should ignore empty Values
> -------------------------------------------
>
>                 Key: CALCITE-1488
>                 URL: https://issues.apache.org/jira/browse/CALCITE-1488
>             Project: Calcite
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 1.10.0
>            Reporter: Gian Merlino
>            Assignee: Julian Hyde
>             Fix For: 1.11.0
>
>
> ValuesReduceRule doesn't propagate rowType on Project of empty Values. If ValuesReduceRule is trying to reduce a Project on top of an empty Values, then changeCount ends up 0, and it returns the underlying Values. This leads to an assertion failure because the returned Values does not have the expected rowType.
> One way to fix this is changing the "Filter had no effect" logic from "{{changeCount == 0}}" to "{{changeCount == 0 && projectExprs == null}}".



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