silundong commented on code in PR #4678:
URL: https://github.com/apache/calcite/pull/4678#discussion_r2610186506
##########
core/src/test/resources/sql/planner.iq:
##########
@@ -215,14 +215,13 @@ select a from (values (1.0), (4.0), (null)) as t3 (a);
!ok
EnumerableAggregate(group=[{0}])
- EnumerableNestedLoopJoin(condition=[IS NOT DISTINCT FROM($0, $1)],
joinType=[semi])
+ EnumerableHashJoin(condition=[IS NOT DISTINCT FROM($0, $1)], joinType=[semi])
EnumerableCalc(expr#0=[{inputs}], expr#1=[CAST($t0):DECIMAL(11, 1)],
A=[$t1])
- EnumerableAggregate(group=[{0}])
- EnumerableNestedLoopJoin(condition=[IS NOT DISTINCT FROM($0, $1)],
joinType=[semi])
- EnumerableCalc(expr#0=[{inputs}], expr#1=[CAST($t0):DECIMAL(11, 1)
NOT NULL], A=[$t1])
- EnumerableValues(tuples=[[{ 1.0 }, { 2.0 }, { 3.0 }, { 4.0 }, {
5.0 }]])
- EnumerableCalc(expr#0=[{inputs}], expr#1=[CAST($t0):DECIMAL(11, 1)
NOT NULL], A=[$t1])
- EnumerableValues(tuples=[[{ 1 }, { 2 }]])
+ EnumerableHashJoin(condition=[IS NOT DISTINCT FROM($0, $1)],
joinType=[semi])
Review Comment:
During the optimization in Volcano, UnionMergeRule merges two Intersects
into one Intersect (three inputs). The two candidate plans are then applied to
IntersectToSemiJoinRule, resulting in:
```
// plan 1 -- two Intersect are respectively applied to the
IntersectToSemiJoinRule
Agg
Join(condition=IS NOT DISTINCT FROM)
Agg
Join(condition=IS NOT DISTINCT FROM)
Input2
Input3
Input1
// plan 2 -- one Intersect with three inputs is applied to
IntersectToSemiJoinRule
Agg
Join(condition=IS NOT DISTINCT FROM)
Join(condition=IS NOT DISTINCT FROM)
Input2
Input3
Input1
```
before this commit, all the joins above were NLJoin, with plan 1 having a
lower cost;
after this commit, all the joins above are HashJoin, with plan 2 having a
lower cost.
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