mihaibudiu commented on code in PR #4714:
URL: https://github.com/apache/calcite/pull/4714#discussion_r2656046064
##########
core/src/test/resources/sql/scalar.iq:
##########
@@ -310,4 +310,97 @@ select
!ok
+# [CALCITE-7348] Remove redundant extraction correlation variables when Trim
Project Fields
+
+!set trimfields true
+
+SELECT empno, (SELECT COUNT(*) AS c
+FROM "scott".emp
+WHERE mgr < "t".mgr) AS "$f1"
+FROM "scott".emp as "t"
+WHERE sal > 10;
++-------+-----+
+| EMPNO | $f1 |
++-------+-----+
+| 7369 | 12 |
+| 7499 | 2 |
+| 7521 | 2 |
+| 7566 | 9 |
+| 7654 | 2 |
+| 7698 | 9 |
+| 7782 | 9 |
+| 7788 | 0 |
+| 7839 | 0 |
+| 7844 | 2 |
+| 7876 | 8 |
+| 7900 | 2 |
+| 7902 | 0 |
+| 7934 | 7 |
++-------+-----+
+(14 rows)
+
+!ok
+EnumerableCalc(expr#0..3=[{inputs}], expr#4=[IS NULL($t3)], expr#5=[0:BIGINT],
expr#6=[CASE($t4, $t5, $t3)], EMPNO=[$t0], $f1=[$t6])
Review Comment:
Reading these plans requires superhuman attention.
Are they really necessary?
##########
core/src/main/java/org/apache/calcite/sql2rel/RelFieldTrimmer.java:
##########
@@ -589,14 +573,14 @@ public TrimResult trimFields(
final List<RexNode> newProjects = new ArrayList<>();
final RexVisitor<RexNode> shuttle;
- if (!correlationIds.isEmpty()) {
- assert correlationIds.size() == 1;
+ if (!project.getVariablesSet().isEmpty()) {
shuttle = new RexPermuteInputsShuttle(inputMapping, newInput) {
@Override public RexNode visitSubQuery(RexSubQuery subQuery) {
subQuery = (RexSubQuery) super.visitSubQuery(subQuery);
return
RelOptUtil.remapCorrelatesInSuqQuery(relBuilder.getRexBuilder(),
- subQuery, correlationIds.iterator().next(), newInput.getRowType(),
inputMapping);
+ subQuery, project.getVariablesSet().iterator().next(),
Review Comment:
There is an implicit assumption that the project has exactly one variable.
Maybe this pattern to extract the variable could be factored into a method
of the Project, which also asserts that there is exactly one such variable.
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