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https://issues.apache.org/jira/browse/CALCITE-3198?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16887746#comment-16887746
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Ruben Quesada Lopez commented on CALCITE-3198:
----------------------------------------------
PR available. As mentioned in the previous comments, the proposed fix is
actually located in {{RexSimplify}}.
> ReduceExpressionsRule.FILTER_INSTANCE does not reduce 'NOT(x=a AND x=b)'
> ------------------------------------------------------------------------
>
> Key: CALCITE-3198
> URL: https://issues.apache.org/jira/browse/CALCITE-3198
> Project: Calcite
> Issue Type: Bug
> Affects Versions: 1.20.0
> Reporter: Ruben Quesada Lopez
> Assignee: Ruben Quesada Lopez
> Priority: Minor
> Labels: pull-request-available
> Fix For: 1.21.0
>
> Time Spent: 10m
> Remaining Estimate: 0h
>
> Currently, ReduceExpressionsRule.FILTER_INSTANCE can successfully reduce a
> query like this one (see RelOptRulesTest#testReduceConstantsDup):
> {code}
> // query:
> select d.deptno from dept d where d.deptno=7 and d.deptno=8
> // plan before:
> LogicalProject(DEPTNO=[$0])
> LogicalFilter(condition=[AND(=($0, 7), =($0, 8))])
> LogicalTableScan(table=[[CATALOG, SALES, DEPT]])
> // plan after:
> LogicalProject(DEPTNO=[$0])
> LogicalValues(tuples=[[]])
> {code}
> As we can see, since the filter is 'always false', the
> LogicalTableScan+LogicalFilter are correctly replaced by an empty
> LogicalValues.
> However, the same filter with a NOT expression, is not correctly simplified:
> {code}
> // query:
> select d.deptno from dept d where not(d.deptno=7 and d.deptno=8)
> // plan before:
> LogicalProject(DEPTNO=[$0])
> LogicalFilter(condition=[NOT(AND(=($0, 7), =($0, 8)))])
> LogicalTableScan(table=[[CATALOG, SALES, DEPT]])
> // plan after (actual, NOT distributivity for AND):
> LogicalProject(DEPTNO=[$0])
> LogicalFilter(condition=[OR(<>($0, 7), <>($0, 8))])
> LogicalTableScan(table=[[CATALOG, SALES, DEPT]])
> // plan after (expected, filter removed):
> LogicalProject(DEPTNO=[$0])
> LogicalTableScan(table=[[CATALOG, SALES, DEPT]])
> {code}
> Since the filter is the negated of an 'always false filter' (the one used in
> the previous query), it is therefore an 'always true filter', so the expected
> behavior is that the LogicalFilter should be removed, and it is not.
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