xiedeyantu commented on code in PR #4557:
URL: https://github.com/apache/calcite/pull/4557#discussion_r2384206942
##########
core/src/test/resources/sql/planner.iq:
##########
@@ -223,15 +224,16 @@ select a from (values (1.0), (4.0), (null)) as t3 (a);
!ok
-EnumerableCalc(expr#0=[{inputs}], expr#1=[CAST($t0):DECIMAL(11, 1)], A=[$t1])
- EnumerableNestedLoopJoin(condition=[OR(AND(IS NULL(CAST($0):DECIMAL(11, 1)),
IS NULL(CAST($1):DECIMAL(11, 1))), =(CAST($0):DECIMAL(11, 1),
CAST($1):DECIMAL(11, 1)))], joinType=[anti])
- EnumerableAggregate(group=[{0}])
- EnumerableNestedLoopJoin(condition=[=(CAST($0):DECIMAL(11, 1) NOT NULL,
CAST($1):DECIMAL(11, 1) NOT NULL)], joinType=[anti])
- EnumerableCalc(expr#0=[{inputs}], expr#1=[CAST($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=[$t1])
- EnumerableValues(tuples=[[{ 1 }, { 2 }]])
- EnumerableCalc(expr#0=[{inputs}], expr#1=[CAST($t0):DECIMAL(11, 1)],
A=[$t1])
+EnumerableCalc(expr#0..1=[{inputs}], expr#2=[CAST($t0):DECIMAL(11, 1)],
A=[$t2])
+ EnumerableHashJoin(condition=[=($1, $3)], joinType=[anti])
+ EnumerableCalc(expr#0=[{inputs}], expr#1=[CAST($t0):DECIMAL(11, 1)],
proj#0..1=[{exprs}])
+ EnumerableAggregate(group=[{0}])
+ EnumerableNestedLoopJoin(condition=[=(CAST($0):DECIMAL(11, 1) NOT
NULL, CAST($1):DECIMAL(11, 1) NOT NULL)], joinType=[anti])
+ EnumerableCalc(expr#0=[{inputs}], expr#1=[CAST($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=[$t1])
+ EnumerableValues(tuples=[[{ 1 }, { 2 }]])
+ EnumerableCalc(expr#0=[{inputs}], expr#1=[CAST($t0):DECIMAL(11, 1)],
A=[$t1], A0=[$t1])
Review Comment:
@asolimando Thank you very much for the explanation. After carefully
debugging, I found that the issue reflected by the `IntersectToSemiJoinRule` is
only superficial. The root cause is that you implemented lossless casting for
the `Decimal` type, which enhances expression simplification capabilities. For
example, in the case of `AND(IS NULL(CAST($0):DECIMAL(11, 1)), IS
NULL(CAST($1):DECIMAL(11, 1)))`, it can be simplified to `false`. This enables
the `JoinPushExpressionsRule` to be successfully applied.
The issue is not actually about multiple casts in the
`IntersectToSemiJoinRule`. I believe that even if multiple repeated `cast`s are
performed, they should be successfully eliminated. Of course, I agree with your
point about optimizing the problem of generating `cast`s at every layer in the
`IntersectToSemiJoinRule`—this should be addressed at another level. Generating
`cast`s at every layer indeed complicates the plan unnecessarily.
Finally, I want to say that your PR is truly very useful. If there are no
further comments, I'm looking forward to this PR being merged as soon as
possible.
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