[jira] [Commented] (CALCITE-2455) simplifyCoalesce of constant should match nullability

["Yuzhao Chen (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-2455?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16574203#comment-16574203 ] 

Yuzhao Chen commented on CALCITE-2455:
--------------------------------------

Hi, [~julianhyde]
I have attach the details and change the head.

> simplifyCoalesce of constant should match nullability
> -----------------------------------------------------
>
>                 Key: CALCITE-2455
>                 URL: https://issues.apache.org/jira/browse/CALCITE-2455
>             Project: Calcite
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 1.17.0
>            Reporter: Yuzhao Chen
>            Assignee: Julian Hyde
>            Priority: Major
>             Fix For: 1.18.0
>
>
> After CALCITE-2227, we will not replace Coalesce to Case When for natural join, when we use ReduceExpressionRule for our plan for Coalesce with constant, the nullability will chage( from nullable to notnull), this will cause VolcanoPlanner to throw error.
> Should i fix this? or we should not use this rule in VolcanoPlanner?
> This is the error thrown sql :
> {code:java}
> select * from lateral (select * from scott_emp) as e
>     join (table scott_dept) using (deptno)
>     where e.deptno = 10 {code}
> The plan before ReduceExpressionRule:
> {code:java}
> LogicalProject(deptno=[COALESCE($7, $8)], empno=[$0], ename=[$1], job=[$2], mgr=    [$3], hiredate=[$4], sal=[$5], comm=[$6], dname=[$9], loc=[$10])
> +- LogicalFilter(condition=[=($7, 10)])
> +- LogicalJoin(condition=[=($7, $8)], joinType=[inner])
> :- LogicalProject(empno=[$0], ename=[$1], job=[$2], mgr=[$3], hiredate=[$4], sal=[$5], comm=[$6], deptno=[$7])
> : +- LogicalTableScan(table=[[scott_emp]])
> +- LogicalProject(deptno=[$0], dname=[$1], loc=[$2])
> +- LogicalTableScan(table=[[scott_dept]])
> {code}
> The plan after:
> {code:java}
> LogicalProject(deptno=[10], empno=[$0], ename=[$1], job=[$2], mgr=[$3], hiredate=[$4], sal=[$5], comm=[$6], dname=[$9], loc=[$10])
> +- LogicalFilter(condition=[=($7, 10)])
> +- LogicalJoin(condition=[=($7, $8)], joinType=[inner])
> :- LogicalProject(empno=[$0], ename=[$1], job=[$2], mgr=[$3], hiredate=[$4], sal=[$5], comm=[$6], deptno=[$7])
> : +- LogicalTableScan(table=[[scott_emp]])
> +- LogicalProject(deptno=[$0], dname=[$1], loc=[$2])
> +- LogicalTableScan(table=[[scott_dept]])
> {code}
> We can see that the deptno's nullability changes from nullable to not null. And we encounter an type error when using  ReduceExpressionRule in VolcanoPlanner.



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