Aaaaaaron commented on a change in pull request #2125:
URL: https://github.com/apache/calcite/pull/2125#discussion_r481684776
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File path: core/src/main/java/org/apache/calcite/sql2rel/RelFieldTrimmer.java
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@@ -885,14 +886,22 @@ public TrimResult trimFields(
/**
* Variant of {@link #trimFields(RelNode, ImmutableBitSet, Set)} for
- * {@link org.apache.calcite.rel.core.SetOp} (including UNION and UNION ALL).
+ * {@link org.apache.calcite.rel.core.SetOp} (Only UNION ALL is supported).
*/
public TrimResult trimFields(
SetOp setOp,
ImmutableBitSet fieldsUsed,
Set<RelDataTypeField> extraFields) {
final RelDataType rowType = setOp.getRowType();
final int fieldCount = rowType.getFieldCount();
+
+ // Trim fields only for UNION ALL.
+ // Operator UNION/INTERSECT/INTERSECT ALL/EXCEPT/EXCEPT ALL
+ // will check duplication. We can not trim fields on them.
+ if (!(setOp.kind == SqlKind.UNION && setOp.all)) {
+ return result(setOp, Mappings.createIdentity(fieldCount));
Review comment:
> Does `INTERSECT ALL` and `EXCEPT ALL` check the duplicates ?
INTERSECT returns the same element in two sets.
```
emp0:
name, deptno
"A", 0
"B", 1
emp1:
name, deptno
"A", 0
"A", 1
select name from
(select name, deptno from emp0
intersect all
select name, deptno from emp1)
```
intersect all (name, deptno) returns (("A", 0), ("A", 0))
intersect all (name) returns (("A"),("A"),("A"))
They are different, all subtraction operation will be affected, tell me if
I'm wrong.
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