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https://issues.apache.org/jira/browse/CALCITE-3466?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16963973#comment-16963973
]
Wang Yanlin commented on CALCITE-3466:
--------------------------------------
{code:java}
select a, avg(c1) from
(
select a,sum(d),b as c1 from t group by b,a
) as t
group by a
{code}
equals to
{code:java}
select a, avg(b) from
(
select a,b from t group by b,a
) as t
group by a
{code}
equals to
{code:java}
select a, avg(b) from
(
select a,b from t group by a, b
) as t
group by a
{code}
equals to
{code:java}
select a, avg(b)
from t
group by a
{code}
> JDBC adapter dropped group by statement in subquery
> ---------------------------------------------------
>
> Key: CALCITE-3466
> URL: https://issues.apache.org/jira/browse/CALCITE-3466
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.21.0, 1.22.0
> Reporter: Wang Weidong
> Priority: Major
> Fix For: 1.22.0
>
>
> While convert RelNode to SqlNode, the "group by" statement in subquery was
> dropped unexpectedly. For example,
> original sql is:
> {code:sql}
> select a, avg(c1) from
> (
> select a,sum(d),b as c1 from t group by b,a
> ) as t
> group by a
> {code}
> RelNode converted by SqlNode is
> {code:sql}
> LogicalAggregate(group=[{0}], EXPR$1=[AVG($1)])
> LogicalProject(A=[$1], C1=[$0])
> LogicalAggregate(group=[{0, 1}], EXPR$1=[SUM($2)])
> LogicalProject(B=[$1], A=[$0], D=[$3])
> EnumerableTableScan(table=[[T_TESTPROJECTMERGE]])
> {code}
> And then convert this RelNode to SqlNode, the sql of SqlNode is like this:
> {code:sql}
> SELECT `A`, AVG(`B`)
> FROM `T`
> GROUP BY `A`
> {code}
> We can find that "group by" in subquery was dropped which may cause SqlNode
> converted by RelNode being not equivalent to RelNode.
> After debugging, I've found code
> at
> https://github.com/apache/calcite/blob/aa98c1575762718b238af8ddd44a390607de7602/core/src/main/java/org/apache/calcite/rel/rel2sql/RelToSqlConverter.java#L333
>
> calls org.apache.calcite.rel.rel2sql.SqlImplementor.Builder#setGroupBy
> without judge whether "group by" already exists.
> Finally, I think in this case, the main select and sub-select shouldn't be
> merged.
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