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Gautam Kumar Parai resolved DRILL-4771. --------------------------------------- Resolution: Fixed Fix Version/s: 1.9.0 Closed with commit: 229571533bce1e37395d9675ea804ee97b1a2362 > Drill should avoid doing the same join twice if count(distinct) exists > ---------------------------------------------------------------------- > > Key: DRILL-4771 > URL: https://issues.apache.org/jira/browse/DRILL-4771 > Project: Apache Drill > Issue Type: Improvement > Affects Versions: 1.2.0 > Reporter: Gautam Kumar Parai > Assignee: Gautam Kumar Parai > Fix For: 1.9.0 > > > When the query has one distinct aggregate and one or more non-distinct > aggregates, the join instance need not produce the join-based plan. We can > generate multi-phase aggregates. Another approach would be to use grouping > sets. However, Drill is unable to support grouping sets and instead relies on > the join-based plan (see the plan below) > {code} > select emp.empno, count(*), avg(distinct dept.deptno) > from sales.emp emp inner join sales.dept dept > on emp.deptno = dept.deptno > group by emp.empno > LogicalProject(EMPNO=[$0], EXPR$1=[$1], EXPR$2=[$3]) > LogicalJoin(condition=[IS NOT DISTINCT FROM($0, $2)], joinType=[inner]) > LogicalAggregate(group=[{0}], EXPR$1=[COUNT()]) > LogicalProject(EMPNO=[$0], DEPTNO0=[$9]) > LogicalJoin(condition=[=($7, $9)], joinType=[inner]) > LogicalTableScan(table=[[CATALOG, SALES, EMP]]) > LogicalTableScan(table=[[CATALOG, SALES, DEPT]]) > LogicalAggregate(group=[{0}], EXPR$2=[AVG($1)]) > LogicalAggregate(group=[{0, 1}]) > LogicalProject(EMPNO=[$0], DEPTNO0=[$9]) > LogicalJoin(condition=[=($7, $9)], joinType=[inner]) > LogicalTableScan(table=[[CATALOG, SALES, EMP]]) > LogicalTableScan(table=[[CATALOG, SALES, DEPT]]) > {code} > The more efficient form should look like this > {code} > select emp.empno, count(*), avg(distinct dept.deptno) > from sales.emp emp inner join sales.dept dept > on emp.deptno = dept.deptno > group by emp.empno > LogicalAggregate(group=[{0}], EXPR$1=[SUM($2)], EXPR$2=[AVG($1)]) > LogicalAggregate(group=[{0, 1}], EXPR$1=[COUNT()]) > LogicalProject(EMPNO=[$0], DEPTNO0=[$9]) > LogicalJoin(condition=[=($7, $9)], joinType=[inner]) > LogicalTableScan(table=[[CATALOG, SALES, EMP]]) > LogicalTableScan(table=[[CATALOG, SALES, DEPT]]) > {code} -- This message was sent by Atlassian JIRA (v6.3.4#6332)