planner: fix name ambiguous check when building natural join without …

…filter (#36012) (#50904)

close #32044

pkg/executor/test/jointest/BUILD.bazel

@@ -9,7 +9,7 @@ go_test(
     ],
     flaky = True,
     race = "on",
-    shard_count = 13,
+    shard_count = 14,
     deps = [
         "//pkg/config",
         "//pkg/meta/autoid",

pkg/executor/test/jointest/join_test.go

@@ -30,6 +30,31 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+func TestIssue30244(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+
+	tk.MustExec("use test;")
+	tk.MustExec("drop table if exists t1,t2,t3,t4;")
+	tk.MustExec("create table t1 (c int, b int);")
+	tk.MustExec("create table t2 (a int, b int);")
+	tk.MustExec("create table t3 (b int, c int);")
+	tk.MustExec("create table t4 (y int, c int);")
+
+	err := tk.ExecToErr("select * from t1 natural join (t3 cross join t4);")
+	require.NotNil(t, err)
+	require.Equal(t, err.Error(), "[planner:1052]Column 'c' in from clause is ambiguous")
+	err = tk.ExecToErr("select * from (t3 cross join t4) natural join t1;")
+	require.NotNil(t, err)
+	require.Equal(t, err.Error(), "[planner:1052]Column 'c' in from clause is ambiguous")
+	err = tk.ExecToErr("select * from (t1 join t2 on t1.b=t2.b) natural join (t3 natural join t4);")
+	require.NotNil(t, err)
+	require.Equal(t, err.Error(), "[planner:1052]Column 'b' in from clause is ambiguous")
+	err = tk.ExecToErr("select * from (t3 natural join t4) natural join (t1 join t2 on t1.b=t2.b);")
+	require.NotNil(t, err)
+	require.Equal(t, err.Error(), "[planner:1052]Column 'b' in from clause is ambiguous")
+}
+
 func TestJoinInDisk(t *testing.T) {
 	origin := config.RestoreFunc()
 	defer origin()

pkg/planner/core/logical_plan_builder.go

@@ -1248,6 +1248,52 @@ func (b *PlanBuilder) coalesceCommonColumns(p *LogicalJoin, leftPlan, rightPlan
 		if err != nil {
 			return err
 		}
+	} else {
+		// Even with no using filter, we still should check the checkAmbiguous name before we try to find the common column from both side.
+		// (t3 cross join t4) natural join t1
+		//  t1 natural join (t3 cross join t4)
+		// t3 and t4 may generate the same name column from cross join.
+		// for every common column of natural join, the name from right or left should be exactly one.
+		commonNames := make([]string, 0, len(lNames))
+		lNameMap := make(map[string]int, len(lNames))
+		rNameMap := make(map[string]int, len(rNames))
+		for _, name := range lNames {
+			// Natural join should ignore _tidb_rowid
+			if name.ColName.L == "_tidb_rowid" {
+				continue
+			}
+			// record left map
+			if cnt, ok := lNameMap[name.ColName.L]; ok {
+				lNameMap[name.ColName.L] = cnt + 1
+			} else {
+				lNameMap[name.ColName.L] = 1
+			}
+		}
+		for _, name := range rNames {
+			// Natural join should ignore _tidb_rowid
+			if name.ColName.L == "_tidb_rowid" {
+				continue
+			}
+			// record right map
+			if cnt, ok := rNameMap[name.ColName.L]; ok {
+				rNameMap[name.ColName.L] = cnt + 1
+			} else {
+				rNameMap[name.ColName.L] = 1
+			}
+			// check left map
+			if cnt, ok := lNameMap[name.ColName.L]; ok {
+				if cnt > 1 {
+					return ErrAmbiguous.GenWithStackByArgs(name.ColName.L, "from clause")
+				}
+				commonNames = append(commonNames, name.ColName.L)
+			}
+		}
+		// check right map
+		for _, commonName := range commonNames {
+			if rNameMap[commonName] > 1 {
+				return ErrAmbiguous.GenWithStackByArgs(commonName, "from clause")
+			}
+		}
 	}
 
 	// Find out all the common columns and put them ahead.