planner: support the leading hint for outer join

planner/core/rule_join_reorder.go

@@ -194,19 +194,15 @@ func (s *joinReOrderSolver) optimizeRecursive(ctx sessionctx.Context, p LogicalP
 		}
 
 		if leadingHintInfo != nil && leadingHintInfo.leadingJoinOrder != nil {
-			if hasOuterJoin {
-				ctx.GetSessionVars().StmtCtx.AppendWarning(ErrInternal.GenWithStack("leading hint is inapplicable when we have outer join"))
-			} else {
-				if useGreedy {
-					ok, leftJoinGroup := baseGroupSolver.generateLeadingJoinGroup(curJoinGroup, leadingHintInfo)
-					if !ok {
-						ctx.GetSessionVars().StmtCtx.AppendWarning(ErrInternal.GenWithStack("leading hint is inapplicable, check if the leading hint table is valid"))
-					} else {
-						curJoinGroup = leftJoinGroup
-					}
+			if useGreedy {
+				ok, leftJoinGroup := baseGroupSolver.generateLeadingJoinGroup(curJoinGroup, leadingHintInfo, hasOuterJoin)
+				if !ok {
+					ctx.GetSessionVars().StmtCtx.AppendWarning(ErrInternal.GenWithStack("leading hint is inapplicable, check if the leading hint table is valid"))
 				} else {
-					ctx.GetSessionVars().StmtCtx.AppendWarning(ErrInternal.GenWithStack("leading hint is inapplicable for the DP join reorder algorithm"))
+					curJoinGroup = leftJoinGroup
 				}
+			} else {
+				ctx.GetSessionVars().StmtCtx.AppendWarning(ErrInternal.GenWithStack("leading hint is inapplicable for the DP join reorder algorithm"))
 			}
 		}
 
@@ -298,7 +294,7 @@ type baseSingleGroupJoinOrderSolver struct {
 	leadingJoinGroup LogicalPlan
 }
 
-func (s *baseSingleGroupJoinOrderSolver) generateLeadingJoinGroup(curJoinGroup []LogicalPlan, hintInfo *tableHintInfo) (bool, []LogicalPlan) {
+func (s *baseSingleGroupJoinOrderSolver) generateLeadingJoinGroup(curJoinGroup []LogicalPlan, hintInfo *tableHintInfo, hasOuterJoin bool) (bool, []LogicalPlan) {
 	var leadingJoinGroup []LogicalPlan
 	leftJoinGroup := make([]LogicalPlan, len(curJoinGroup))
 	copy(leftJoinGroup, curJoinGroup)
@@ -324,6 +320,10 @@ func (s *baseSingleGroupJoinOrderSolver) generateLeadingJoinGroup(curJoinGroup [
 		var usedEdges []*expression.ScalarFunction
 		var joinType JoinType
 		leadingJoin, leadingJoinGroup[0], usedEdges, joinType = s.checkConnection(leadingJoin, leadingJoinGroup[0])
+		if hasOuterJoin && usedEdges == nil {
+			// If the joinGroups contain the outer join, we disable the cartesian product.
+			return false, nil
+		}
 		leadingJoin, s.otherConds = s.makeJoin(leadingJoin, leadingJoinGroup[0], usedEdges, joinType)
 		leadingJoinGroup = leadingJoinGroup[1:]
 	}

planner/core/rule_join_reorder_test.go

@@ -79,22 +79,6 @@ func TestLeadingJoinHint(t *testing.T) {
 	tk.MustExec("create table t8(a int, b int, key(a));")
 	runJoinReorderTestData(t, tk, "TestLeadingJoinHint")
 
-	// test cases for outer join
-	tk.MustExec("select /*+ leading(t1, t3) */ * from t1 left join t2 on t1.a=t2.a left join t3 on t2.b=t3.b")
-	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1815 leading hint is inapplicable when we have outer join"))
-	tk.MustExec("select /*+ leading(t2) */ * from t1 left join t2 on t1.a=t2.a left join t3 on t2.b=t3.b")
-	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1815 leading hint is inapplicable when we have outer join"))
-	tk.MustExec("select /*+ leading(t2, t3) */ * from t1 left join t2 on t1.a=t2.a left join t3 on t2.b=t3.b")
-	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1815 leading hint is inapplicable when we have outer join"))
-	tk.MustExec("select /*+ leading(t1, t2, t3) */ * from t1 left join t2 on t1.a=t2.a left join t3 on t2.b=t3.b")
-	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1815 leading hint is inapplicable when we have outer join"))
-	tk.MustExec("select /*+ leading(t1, t3) */ * from t1 join t2 on t1.a=t2.a left join t3 on t2.b=t3.b")
-	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1815 leading hint is inapplicable when we have outer join"))
-	tk.MustExec("select /*+ leading(t1, t2) */ * from t1 join t2 on t1.a=t2.a left join t3 on t2.b=t3.b")
-	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1815 leading hint is inapplicable when we have outer join"))
-	tk.MustExec("select /*+ leading(t3) */ * from t1 join t2 on t1.a=t2.a left join t3 on t2.b=t3.b")
-	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1815 leading hint is inapplicable when we have outer join"))
-
 	// test cases for multiple leading hints
 	tk.MustExec("select /*+ leading(t1) leading(t2) */ * from t1 join t2 on t1.a=t2.a join t3 on t2.b=t3.b")
 	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1815 We can only use one leading hint at most, when multiple leading hints are used, all leading hints will be invalid"))
@@ -166,13 +150,6 @@ func TestJoinOrderHint(t *testing.T) {
 	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1815 There are no matching table names for (t1) in optimizer hint /*+ LEADING(t2, t1) */. Maybe you can use the table alias name",
 		"Warning 1815 leading hint is inapplicable, check if the leading hint table is valid"))
 
-	// conflict between table names
-	tk.MustExec("select /*+ leading(t3) */ * from t1 join t2 on t1.a=t2.a left join t3 on t2.b=t3.b")
-	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1815 leading hint is inapplicable when we have outer join"))
-
-	tk.MustExec("select /*+ leading(t1, t3) */ * from t1 join t2 on t1.a=t2.a left join t3 on t2.b=t3.b")
-	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1815 leading hint is inapplicable when we have outer join"))
-
 	// table name in leading hint cross query block
 	// Todo: Can not handle this case yet. Because when we extract the join group, it will get the join group {t1, t2, t3}.
 	// So the table 't4' can not be used.
@@ -329,3 +306,22 @@ func TestJoinOrderHint4Subquery(t *testing.T) {
 
 	runJoinReorderTestData(t, tk, "TestJoinOrderHint4Subquery")
 }
+
+func TestLeadingJoinHint4OuterJoin(t *testing.T) {
+	store, clean := testkit.CreateMockStore(t)
+	defer clean()
+
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t, t1, t2, t3, t4, t5, t6, t7, t8;")
+	tk.MustExec("create table t(a int, b int, key(a));")
+	tk.MustExec("create table t1(a int, b int, key(a));")
+	tk.MustExec("create table t2(a int, b int, key(a));")
+	tk.MustExec("create table t3(a int, b int, key(a));")
+	tk.MustExec("create table t4(a int, b int, key(a));")
+	tk.MustExec("create table t5(a int, b int, key(a));")
+	tk.MustExec("create table t6(a int, b int, key(a));")
+	tk.MustExec("create table t7(a int, b int, key(a));")
+	tk.MustExec("create table t8(a int, b int, key(a));")
+	runJoinReorderTestData(t, tk, "TestLeadingJoinHint4OuterJoin")
+}

planner/core/testdata/join_reorder_suite_in.json

@@ -298,5 +298,66 @@
       "select /*+ leading(t1, t2@sel_2) */ t1.a, (select min(t2.a) from t2) from t1 join t3 on t1.a = t3.a;",
       "select /*+ leading(t3, t2@sel_2) */ t1.a, (select min(t2.a) from t2) from t1 join t3 on t1.a = t3.a;"
     ]
+  },
+  {
+    "name": "TestLeadingJoinHint4OuterJoin",
+    "cases": [
+      "select /*+ leading(t3, t2) */ * from t2 left join t1 on t2.a=t1.a left join t3 on t1.b=t3.b;",
+      "select /*+ leading(t3, t1) */ * from t2 left join t1 on t2.a=t1.a left join t3 on t1.b=t3.b;",
+      "select /*+ leading(t1, t2) */ * from t2 left join t1 on t2.a=t1.a left join t3 on t1.b=t3.b;",
+      "select /*+ leading(t3) */ * from t2 left join t1 on t2.a=t1.a left join t3 on t1.b=t3.b;",
+      "select /*+ leading(t2) */ * from t2 left join t1 on t2.a=t1.a left join t3 on t1.b=t3.b;",
+      "select /*+ leading(t1) */ * from t2 left join t1 on t2.a=t1.a left join t3 on t1.b=t3.b;",
+      "select /*+ leading(t3, t2, t1) */ * from t2 left join t1 on t2.a=t1.a left join t3 on t1.b=t3.b;",
+      "select /*+ leading(t1, t2, t3) */ * from t2 left join t1 on t2.a=t1.a left join t3 on t1.b=t3.b;",
+      "select /*+ leading(t3, t1, t2) */ * from t2 left join t1 on t2.a=t1.a left join t3 on t1.b=t3.b;",
+      "select /*+ leading(t2) */ * from t2 left join (t1 left join t3 on t1.a=t3.a) on t2.a=1;",
+      "select /*+ leading(t1) */ * from t2 left join (t1 left join t3 on t1.a=t3.a) on t2.a=1;",
+      "select /*+ leading(t3) */ * from t2 left join (t1 left join t3 on t1.a=t3.a) on t2.a=1;",
+      "select /*+ leading(t2, t1) */ * from t2 left join (t1 left join t3 on t1.a=t3.a) on t2.a=1;",
+      "select /*+ leading(t2, t3) */ * from t2 left join (t1 left join t3 on t1.a=t3.a) on t2.a=1;",
+      "select /*+ leading(t3, t1) */ * from t2 left join (t1 left join t3 on t1.a=t3.a) on t2.a=1;",
+      "select /*+ leading(t2, t1, t3) */ * from t2 left join (t1 left join t3 on t1.a=t3.a) on t2.a=1;",
+      "select /*+ leading(t1, t3, t2) */ * from t2 left join (t1 left join t3 on t1.a=t3.a) on t2.a=1;",
+      "select /*+ leading(t2, t3, t1) */ * from t2 left join (t1 left join t3 on t1.a=t3.a) on t2.a=1;",
+      "select /*+ leading(t1) */ * from t2 left join (t1 left join t3 on t1.a=t3.a) on t2.a=t3.a;",
+      "select /*+ leading(t2) */ * from t2 left join (t1 left join t3 on t1.a=t3.a) on t2.a=t3.a;",
+      "select /*+ leading(t3) */ * from t2 left join (t1 left join t3 on t1.a=t3.a) on t2.a=t3.a;",
+      "select /*+ leading(t1, t2) */ * from t2 left join (t1 left join t3 on t1.a=t3.a) on t2.a=t3.a;",
+      "select /*+ leading(t3, t2) */ * from t2 left join (t1 left join t3 on t1.a=t3.a) on t2.a=t3.a;",
+      "select /*+ leading(t1, t3) */ * from t2 left join (t1 left join t3 on t1.a=t3.a) on t2.a=t3.a;",
+      "select /*+ leading(t1, t2, t3) */ * from t2 left join (t1 left join t3 on t1.a=t3.a) on t2.a=t3.a;",
+      "select /*+ leading(t3, t1, t2) */ * from t2 left join (t1 left join t3 on t1.a=t3.a) on t2.a=t3.a;",
+      "select /*+ leading(t1) */ * from (t1 left join t2 on t1.a=t2.a) left join (t3 left join t4 on t3.a=t4.a) on t2.a=t4.a;",
+      "select /*+ leading(t2) */ * from (t1 left join t2 on t1.a=t2.a) left join (t3 left join t4 on t3.a=t4.a) on t2.a=t4.a;",
+      "select /*+ leading(t3) */ * from (t1 left join t2 on t1.a=t2.a) left join (t3 left join t4 on t3.a=t4.a) on t2.a=t4.a;",
+      "select /*+ leading(t4) */ * from (t1 left join t2 on t1.a=t2.a) left join (t3 left join t4 on t3.a=t4.a) on t2.a=t4.a;",
+      "select /*+ leading(t1, t2) */ * from (t1 left join t2 on t1.a=t2.a) left join (t3 left join t4 on t3.a=t4.a) on t2.a=t4.a;",
+      "select /*+ leading(t1, t3) */ * from (t1 left join t2 on t1.a=t2.a) left join (t3 left join t4 on t3.a=t4.a) on t2.a=t4.a;",
+      "select /*+ leading(t4, t1) */ * from (t1 left join t2 on t1.a=t2.a) left join (t3 left join t4 on t3.a=t4.a) on t2.a=t4.a;",
+      "select /*+ leading(t4, t2) */ * from (t1 left join t2 on t1.a=t2.a) left join (t3 left join t4 on t3.a=t4.a) on t2.a=t4.a;",
+      "select /*+ leading(t3, t2) */ * from (t1 left join t2 on t1.a=t2.a) left join (t3 left join t4 on t3.a=t4.a) on t2.a=t4.a;",
+      "select /*+ leading(t3, t4) */ * from (t1 left join t2 on t1.a=t2.a) left join (t3 left join t4 on t3.a=t4.a) on t2.a=t4.a;",
+      "select /*+ leading(t1, t2, t3) */ * from (t1 left join t2 on t1.a=t2.a) left join (t3 left join t4 on t3.a=t4.a) on t2.a=t4.a;",
+      "select /*+ leading(t1, t4, t3) */ * from (t1 left join t2 on t1.a=t2.a) left join (t3 left join t4 on t3.a=t4.a) on t2.a=t4.a;",
+      "select /*+ leading(t4, t2, t3) */ * from (t1 left join t2 on t1.a=t2.a) left join (t3 left join t4 on t3.a=t4.a) on t2.a=t4.a;",
+      "select /*+ leading(t1, t2, t3, t4) */ * from (t1 left join t2 on t1.a=t2.a) left join (t3 left join t4 on t3.a=t4.a) on t2.a=t4.a;",
+      "select /*+ leading(t1) */ * from ((select t8.a, t8.b from t8, t7, t6, t5 where t5.a = t6.a and t6.b=t7.b) t3 left join t4 on t3.a=t4.a) left join (t1 left join t2 on t1.a=t2.a) on t1.a=t4.a;",
+      "select /*+ leading(t2) */ * from ((select t8.a, t8.b from t8, t7, t6, t5 where t5.a = t6.a and t6.b=t7.b) t3 left join t4 on t3.a=t4.a) left join (t1 left join t2 on t1.a=t2.a) on t1.a=t4.a;",
+      "select /*+ leading(t3) */ * from ((select t8.a, t8.b from t8, t7, t6, t5 where t5.a = t6.a and t6.b=t7.b) t3 left join t4 on t3.a=t4.a) left join (t1 left join t2 on t1.a=t2.a) on t1.a=t4.a;",
+      "select /*+ leading(t4) */ * from ((select t8.a, t8.b from t8, t7, t6, t5 where t5.a = t6.a and t6.b=t7.b) t3 left join t4 on t3.a=t4.a) left join (t1 left join t2 on t1.a=t2.a) on t1.a=t4.a;",
+      "select /*+ leading(t2, t1) */ * from ((select t8.a, t8.b from t8, t7, t6, t5 where t5.a = t6.a and t6.b=t7.b) t3 left join t4 on t3.a=t4.a) left join (t1 left join t2 on t1.a=t2.a) on t1.a=t4.a;",
+      "select /*+ leading(t2, t3) */ * from ((select t8.a, t8.b from t8, t7, t6, t5 where t5.a = t6.a and t6.b=t7.b) t3 left join t4 on t3.a=t4.a) left join (t1 left join t2 on t1.a=t2.a) on t1.a=t4.a;",
+      "select /*+ leading(t4, t1) */ * from ((select t8.a, t8.b from t8, t7, t6, t5 where t5.a = t6.a and t6.b=t7.b) t3 left join t4 on t3.a=t4.a) left join (t1 left join t2 on t1.a=t2.a) on t1.a=t4.a;",
+      "select /*+ leading(t3, t1) */ * from ((select t8.a, t8.b from t8, t7, t6, t5 where t5.a = t6.a and t6.b=t7.b) t3 left join t4 on t3.a=t4.a) left join (t1 left join t2 on t1.a=t2.a) on t1.a=t4.a;",
+      "select * from ((select /*+ leading(t5) */ t8.a, t8.b from t8, t7, t6, t5 where t5.a = t6.a and t6.b=t7.b) t3 left join t4 on t3.a=t4.a) left join (t1 left join t2 on t1.a=t2.a) on t1.a=t4.a;",
+      "select * from ((select /*+ leading(t6) */ t8.a, t8.b from t8, t7, t6, t5 where t5.a = t6.a and t6.b=t7.b) t3 left join t4 on t3.a=t4.a) left join (t1 left join t2 on t1.a=t2.a) on t1.a=t4.a;",
+      "select * from ((select /*+ leading(t5, t7) */ t8.a, t8.b from t8, t7, t6, t5 where t5.a = t6.a and t6.b=t7.b) t3 left join t4 on t3.a=t4.a) left join (t1 left join t2 on t1.a=t2.a) on t1.a=t4.a;",
+      "select * from ((select /*+ leading(t6, t8, t7) */ t8.a, t8.b from t8, t7, t6, t5 where t5.a = t6.a and t6.b=t7.b) t3 left join t4 on t3.a=t4.a) left join (t1 left join t2 on t1.a=t2.a) on t1.a=t4.a;",
+      "select /*+ leading(t3) */ * from ((select /*+ leading(t5) */ t8.a, t8.b from t8, t7, t6, t5 where t5.a = t6.a and t6.b=t7.b) t3 left join t4 on t3.a=t4.a) left join (t1 left join t2 on t1.a=t2.a) on t1.a=t4.a;",
+      "select /*+ leading(t3, t1) */ * from ((select /*+ leading(t7) */ t8.a, t8.b from t8, t7, t6, t5 where t5.a = t6.a and t6.b=t7.b) t3 left join t4 on t3.a=t4.a) left join (t1 left join t2 on t1.a=t2.a) on t1.a=t4.a;",
+      "select /*+ leading(t3, t1, t2) */ * from ((select /*+ leading(t6, t7) */ t8.a, t8.b from t8, t7, t6, t5 where t5.a = t6.a and t6.b=t7.b) t3 left join t4 on t3.a=t4.a) left join (t1 left join t2 on t1.a=t2.a) on t1.a=t4.a;",
+      "select /*+ leading(t3, t4) */ * from ((select /*+ leading(t5, t7, t8) */ t8.a, t8.b from t8, t7, t6, t5 where t5.a = t6.a and t6.b=t7.b) t3 left join t4 on t3.a=t4.a) left join (t1 left join t2 on t1.a=t2.a) on t1.a=t4.a;"
+    ]
   }
 ]