Re: SQL has order by, there will be one more column(the sort column) in result plan

[JiaTao Tao]

Thanks, Julian

I can see the fields in RelRoot, and I'm a little confused, I want to
use RelVisitor to visit the RelNode, and here comes the RelRoot, any advice
to deal with RelRoot when using RelVisitor?


Regards!

Aron Tao


Julian Hyde <jh...@apache.org> 于2020年3月5日周四 上午2:03写道：

> There is a class RelRoot that wraps the top-most RelNode, and projects
> away columns that are only used for sorting. Read through
> https://issues.apache.org/jira/browse/CALCITE-2999 <
> https://issues.apache.org/jira/browse/CALCITE-2999>, where someone had
> the same misunderstanding that you have.
>
>
> > On Mar 4, 2020, at 3:43 AM, JiaTao Tao <t...@apache.org> wrote:
> >
> > SQL;
> > ```
> > SELECT u.ID, u.NAME
> > FROM USERS u
> > ORDER BY u.AGE
> > ```
> >
> > PLAN:
> > ```
> > LogicalSort(sort0=[$2], dir0=[ASC])
> >  LogicalProject(ID=[$0], NAME=[$1], AGE=[$2])
> >    EnumerableTableScan(table=[[RECR, USERS]])
> > ```
> > Plan's row type: RecordType(INTEGER ID, VARCHAR NAME, INTEGER AGE)
> >
> > But the SQL only project ID and NAME, there should be a LogicalProject
> > (ID, NAME) on LogicalSort. Is this by design? And what about this extra
> > column?
> >
> >
> >
> > Regards!
> >
> > Aron Tao
>
>