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https://issues.apache.org/jira/browse/CALCITE-6817?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17924826#comment-17924826
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ZheHu commented on CALCITE-6817:
--------------------------------

It seems RelWriter is a way to go if we want more plan detail to print.
I'm considering adding a new method (call expand()) in RelWriter, and adding a 
new toString() method in RelOptUtil that allows user to set expand flag. What 
do you guys think?
As you mentioned above, where should I look for "the nullability of fields of 
complex types". I assume types like ArraySqlType, MapSqlType and 
MultisetSqlType. And what kind of format do you think is suitable? [~mbudiu] 
[~suibianwanwan33]

> Add string representation of default nulls direction for RelNode
> ----------------------------------------------------------------
>
>                 Key: CALCITE-6817
>                 URL: https://issues.apache.org/jira/browse/CALCITE-6817
>             Project: Calcite
>          Issue Type: Improvement
>          Components: core
>    Affects Versions: 1.38.0
>            Reporter: ZheHu
>            Assignee: ZheHu
>            Priority: Minor
>              Labels: pull-request-available
>
> Calcite has the same hehavior with Oracle on returning the null direction if 
> not specified, which means NULLS LAST is assumed for ASC and NULLS FIRST is 
> assumed for DESC.
> However, the default nulls direction is not presented in plan traces. For 
> example:
> {code:java}
> select empno from emp order by empno desc
> {code}
> has the following plan:
> {code:java}
> LogicalSort(sort0=[$0], dir0=[DESC])
>   LogicalProject(EMPNO=[$0])
>     LogicalTableScan(table=[[CATALOG, SALES, EMP]])
> {code}
> It makes RelNode clearer if adding nulls direction, so the above plan will be 
> like:
> {code:java}
> LogicalSort(sort0=[$0], dir0=[DESC-nulls-first])
>   LogicalProject(EMPNO=[$0])
>     LogicalTableScan(table=[[CATALOG, SALES, EMP]])
> {code}



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