zabetak commented on code in PR #2911:
URL: https://github.com/apache/calcite/pull/2911#discussion_r975061171
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core/src/main/java/org/apache/calcite/sql2rel/RelFieldTrimmer.java:
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@@ -481,6 +481,18 @@ public TrimResult trimFields(
final int fieldCount = rowType.getFieldCount();
final RelNode input = project.getInput();
+ boolean containsSubQuery = false;
+ for (RexNode node : project.getProjects()) {
+ if (RexUtil.containsSubQuery(node)) {
+ containsSubQuery = true;
+ break;
+ }
+ }
+ // Do not trim Project's fields before SubQueryRemoveRule applies.
+ if (containsSubQuery) {
+ return result(project, Mappings.createIdentity(fieldCount));
+ }
+
Review Comment:
I didn't notice that the new test in `sub-query.iq` was passing from here,
great! Since there are tests then I guess it is OK to keep the changes as part
of this PR.
> If there is a test case which is affected by this change, then it was
already wrong.
It may be wrong but not always, right? This is a rough check as we discussed
not precise.
Moreover if there is a sub-query in the top project then field trimmer will
stop without doing anything. I think we can do better than that. Is it valid to
trim its input? I mean something like the following:
```java
if (containsSubQuery) {
return trimFields((RelNode) project, fieldsUsed, extraFields);
}
```
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