Dwrite commented on code in PR #4692:
URL: https://github.com/apache/calcite/pull/4692#discussion_r2645766735
##########
core/src/main/java/org/apache/calcite/sql/dialect/ClickHouseSqlDialect.java:
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@@ -404,4 +411,45 @@ private static void unparseFloor(SqlWriter writer, SqlCall
call) {
call.operand(0).unparse(writer, 0, 0);
writer.endList(frame);
}
+
+ @Override public boolean shouldWrapNestedJoin(RelNode rel) {
+ if (!(rel instanceof Join)) {
+ return false;
+ }
+ Join join = (Join) rel;
+
+ // ClickHouse primarily requires wrapping the right side of a JOIN
+ // when it contains a nested JOIN
+ return containsJoinRecursive(join.getRight());
+ }
+
+ /**
+ * Checks whether the given RelNode contains a JOIN that is directly exposed
+ * at the JOIN boundary, possibly wrapped by a small number of transparent
+ * single-input operators (e.g. Project, Filter, Sort).
+ *
+ * <p>This method intentionally does NOT perform a full tree traversal.
+ * ClickHouse only requires wrapping when a JOIN appears directly as a JOIN
input;
+ * JOINs deeper in the subtree do not trigger the restriction.
+ *
+ * <p>Therefore, a full RelVisitor is avoided here to prevent over-detection
+ * and unnecessary wrapping.
+ */
+ private static boolean containsJoinRecursive(RelNode rel) {
+ if (rel instanceof Join || rel instanceof Correlate) {
+ return true;
+ }
+
+ // Look through transparent single-input operators
+ // These don't create subquery boundaries in the SQL
+ if (rel instanceof Project
+ || rel instanceof Filter
+ || rel instanceof Sort
+ || rel instanceof Aggregate) { // Add Aggregate here
Review Comment:
sure. removed
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