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https://issues.apache.org/jira/browse/CALCITE-3893?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17073656#comment-17073656
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Feng Zhu commented on CALCITE-3893:
-----------------------------------
[~icshuo], according to the discussion, we will rewrite the query
{code:java}
select deptno, group_id() as g, count(*) as c
from emp
group by grouping sets (deptno, (), ())
{code}
as
{code:java}
select deptno, 0 as g, count(*) as c
from emp
group by grouping sets (deptno, ())
union all
select null, 1 as g, count(*) as c
from emp
group by grouping sets (())
{code}
Hence, the second sub-query's 'groupSet' should be empty (i.e., *group=[{}]*).
To validate it, you can convert it back to SQL, which will fail the validation
due to 'deptno is not being grouped'.
{code:java}
LogicalAggregate(group=[{0}], groups=[[{}]], C=[COUNT()])
LogicalProject(DEPTNO=[$7])
LogicalTableScan(table=[[CATALOG, SALES, EMP]])
--------------------------------------------------------------------
select deptno, count(*) as c
from emp
group by grouping sets (())
{code}
> SQL with GROUP_ID may generate wrong plan
> -----------------------------------------
>
> Key: CALCITE-3893
> URL: https://issues.apache.org/jira/browse/CALCITE-3893
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.22.0
> Reporter: Shuo Cheng
> Priority: Major
> Fix For: 1.23.0
>
>
> Consider the following SQL:
> {code:java}
> select
> deptno, group_id() as g, count(*) as c
> from emp
> group by grouping sets (deptno, (), ())
> {code}
> the plan after SqlToRel is:
> {code:java}
> LogicalUnion(all=[true])
> LogicalProject(DEPTNO=[$0], G=[0:BIGINT], C=[$1])
> LogicalAggregate(group=[{0}], groups=[[{0}, {}]], C=[COUNT()])
> LogicalProject(DEPTNO=[$7])
> LogicalTableScan(table=[[CATALOG, SALES, EMP]])
> LogicalProject(DEPTNO=[$0], G=[1:BIGINT], C=[$1])
> LogicalAggregate(group=[{0}], groups=[[{}]], C=[COUNT()])
> LogicalProject(DEPTNO=[$7])
> LogicalTableScan(table=[[CATALOG, SALES, EMP]])
> {code}
> I'm afraid there's some semantic problems here. As `groups` of the second
> Aggregate is empty, then what is `$0` meaning in the Project above it. Maybe
> that we want is:
> {code:java}
> LogicalUnion(all=[true])
> LogicalProject(DEPTNO=[$0], G=[0:BIGINT], C=[$1])
> LogicalAggregate(group=[{0}], groups=[[{0}, {}]], C=[COUNT()])
> LogicalProject(DEPTNO=[$7])
> LogicalTableScan(table=[[CATALOG, SALES, EMP]])
> LogicalProject(DEPTNO=[$0], G=[1:BIGINT], C=[$1])
> LogicalAggregate(group=[{0}], groups=[[{0}]], C=[COUNT()])
> LogicalProject(DEPTNO=[null])
> LogicalTableScan(table=[[CATALOG, SALES, EMP]]){code}
> I noticed this is introduced by CALCITE-1824, cc [~donnyzone],
> [~vladimirsitnikov].
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