HIVE-29249: RuntimeException in PlanModifierForASTConv.introduceDerivedTable for queries with self joins

The problem occurs when we need to introduce a derived table over the left input of the join but the input is already modified (newL) by the shuttle.
Looking for the modified input in the join's children fails and raises an exception. Since we know which input needs to be replaced we can avoid the lookup mechanism in
`introduceDerivedTable(RelNode, RelNode)` and build directly the new join operator via copy.

To avoid unnecessary object creation bubling further up via the HiveRelShuttle mechansim we perform the copy *only* when one of the inputs is modified.

Author: zabetak

ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/translator/PlanModifierForASTConv.java

@@ -229,12 +229,16 @@ public RelNode visit(HiveJoin join) {
         // No self-join detected, return the join as is
         aliases.addAll(lf.aliases);
         aliases.addAll(rf.aliases);
+      } else {
+        // Self-join detected, introduce a derived table for the left side
+        aliases.addAll(rf.aliases);
+        newL = introduceDerivedTable(newL);
+      }
+      if (newL == join.getLeft() && newR == join.getRight()) {
+        return join;
+      } else {
         return join.copy(join.getTraitSet(), Arrays.asList(newL, newR));
       }
-      // Self-join detected, introduce a derived table for the left side
-      aliases.addAll(rf.aliases);
-      introduceDerivedTable(newL, join);
-      return join;
     }
 
     @Override

ql/src/test/queries/clientpositive/cbo_self_join_ambiguous_alias_cte.q

@@ -3,4 +3,9 @@ create table t1 (key int, value int);
 explain cbo
 with cte as
 (select key, value, BLOCK__OFFSET__INSIDE__FILE, INPUT__FILE__NAME, ROW__ID, ROW__IS__DELETED from t1)
-select * from cte a join cte b join cte c 
+select * from cte a join cte b join cte c;
+
+explain cbo
+with cte as
+(select key, value, BLOCK__OFFSET__INSIDE__FILE, INPUT__FILE__NAME, ROW__ID, ROW__IS__DELETED from t1)
+select * from cte a join t1 b join cte c;

ql/src/test/results/clientpositive/llap/cbo_self_join_ambiguous_alias_cte.q.out

@@ -32,3 +32,29 @@ HiveProject(a.key=[$0], a.value=[$1], a.block__offset__inside__file=[$2], a.inpu
         HiveTableScan(table=[[default, t1]], table:alias=[t1])
     HiveTableScan(table=[[default, t1]], table:alias=[t1])
 
+Warning: Shuffle Join MERGEJOIN[13][tables = [t1, $hdt$_0]] in Stage 'Reducer 2' is a cross product
+Warning: Shuffle Join MERGEJOIN[14][tables = [$hdt$_0, t1]] in Stage 'Reducer 3' is a cross product
+PREHOOK: query: explain cbo
+with cte as
+(select key, value, BLOCK__OFFSET__INSIDE__FILE, INPUT__FILE__NAME, ROW__ID, ROW__IS__DELETED from t1)
+select * from cte a join t1 b join cte c
+PREHOOK: type: QUERY
+PREHOOK: Input: default@t1
+#### A masked pattern was here ####
+POSTHOOK: query: explain cbo
+with cte as
+(select key, value, BLOCK__OFFSET__INSIDE__FILE, INPUT__FILE__NAME, ROW__ID, ROW__IS__DELETED from t1)
+select * from cte a join t1 b join cte c
+POSTHOOK: type: QUERY
+POSTHOOK: Input: default@t1
+#### A masked pattern was here ####
+CBO PLAN:
+HiveProject(a.key=[$0], a.value=[$1], a.block__offset__inside__file=[$2], a.input__file__name=[$3], a.row__id=[$4], a.row__is__deleted=[$5], b.key=[$6], b.value=[$7], c.key=[$8], c.value=[$9], c.block__offset__inside__file=[$10], c.input__file__name=[$11], c.row__id=[$12], c.row__is__deleted=[$13])
+  HiveJoin(condition=[true], joinType=[inner], algorithm=[none], cost=[not available])
+    HiveProject(key=[$0], value=[$1], BLOCK__OFFSET__INSIDE__FILE=[$2], INPUT__FILE__NAME=[$3], ROW__ID=[$4], ROW__IS__DELETED=[$5], key0=[$6], value0=[$7])
+      HiveJoin(condition=[true], joinType=[inner], algorithm=[none], cost=[not available])
+        HiveTableScan(table=[[default, t1]], table:alias=[t1])
+        HiveProject(key=[$0], value=[$1])
+          HiveTableScan(table=[[default, t1]], table:alias=[b])
+    HiveTableScan(table=[[default, t1]], table:alias=[t1])
+