mihaibudiu commented on code in PR #4692:
URL: https://github.com/apache/calcite/pull/4692#discussion_r2628053084
##########
core/src/main/java/org/apache/calcite/sql/SqlDialect.java:
##########
@@ -1825,4 +1825,7 @@ private ContextImpl(DatabaseProduct databaseProduct,
conformance, nullCollation, dataTypeSystem, jethroInfo);
}
}
+ public boolean mustWrapNestedJoin(RelNode relNode) {
Review Comment:
Please document this function.
##########
core/src/main/java/org/apache/calcite/rel/rel2sql/RelToSqlConverter.java:
##########
@@ -233,7 +297,13 @@ public Result visit(Join e) {
break;
}
final Result leftResult = visitInput(e, 0).resetAlias();
- final Result rightResult = visitInput(e, 1).resetAlias();
+ Result rightResult = visitInput(e, 1).resetAlias();
+
+ if (dialect.mustWrapNestedJoin(e)) {
Review Comment:
Can this alias conflict with an existing relation name that is in scope?
Please add a test for this case.
##########
core/src/main/java/org/apache/calcite/sql/dialect/ClickHouseSqlDialect.java:
##########
@@ -404,4 +411,37 @@ private static void unparseFloor(SqlWriter writer, SqlCall
call) {
call.operand(0).unparse(writer, 0, 0);
writer.endList(frame);
}
+
+ @Override public boolean mustWrapNestedJoin(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());
+ }
+
+ /**
+ * Recursively checks if a RelNode contains a JOIN, looking through
+ * transparent single-input operators.
+ */
+ private static boolean containsJoinRecursive(RelNode rel) {
Review Comment:
Isn't a visitor a better tool to do this?
##########
core/src/test/java/org/apache/calcite/rel/rel2sql/RelToSqlConverterTest.java:
##########
@@ -11462,4 +11463,196 @@ public Sql schema(CalciteAssert.SchemaSpec
schemaSpec) {
relFn, transforms);
}
}
+
Review Comment:
I am assuming you have validated these against clickhouse
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