planner: fix false negative "full group by" check for agg in subquery

planner/core/expression_rewriter_test.go

@@ -15,6 +15,8 @@ package core_test
 
 import (
 	. "github.com/pingcap/check"
+	"github.com/pingcap/parser/terror"
+	"github.com/pingcap/tidb/planner/core"
 	"github.com/pingcap/tidb/util/testkit"
 	"github.com/pingcap/tidb/util/testleak"
 	"github.com/pingcap/tidb/util/testutil"
@@ -223,3 +225,20 @@ func (s *testExpressionRewriterSuite) TestCompareSubquery(c *C) {
 	))
 	tk.MustQuery("select * from t t1 where b = all (select a from t t2)").Check(testkit.Rows())
 }
+
+func (s *testExpressionRewriterSuite) TestCheckFullGroupBy(c *C) {
+	defer testleak.AfterTest(c)()
+	store, dom, err := newStoreWithBootstrap()
+	c.Assert(err, IsNil)
+	tk := testkit.NewTestKit(c, store)
+	defer func() {
+		dom.Close()
+		store.Close()
+	}()
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("create table t(a int, b int)")
+	tk.MustQuery("select t1.a, (select max(t2.b) from t t2) from t t1").Check(testkit.Rows())
+	err = tk.ExecToErr("select t1.a, (select t2.a, max(t2.b) from t t2) from t t1")
+	c.Assert(terror.ErrorEqual(err, core.ErrMixOfGroupFuncAndFields), IsTrue, Commentf("err %v", err))
+}

planner/core/logical_plan_builder.go

@@ -1693,6 +1693,8 @@ func (c *colResolverForOnlyFullGroupBy) Enter(node ast.Node) (ast.Node, bool) {
 			c.firstNonAggCol, c.firstNonAggColIdx = t.Name, c.exprIdx
 		}
 		return node, true
+	case *ast.SubqueryExpr:
+		return node, true
 	}
 	return node, false
 }