cherry pick pingcap#30773 to release-5.0

Signed-off-by: ti-srebot <[email protected]>

executor/aggregate_test.go

@@ -1467,5 +1467,6 @@ func (s *testSuiteAgg) TestAvgDecimal(c *C) {
 	tk.MustExec("insert into td values (0,29815);")
 	tk.MustExec("insert into td values (10017,-32661);")
 	tk.MustQuery(" SELECT AVG( col_bigint / col_smallint) AS field1 FROM td;").Sort().Check(testkit.Rows("25769363061037.62077260"))
+	tk.MustQuery(" SELECT AVG(col_bigint) OVER (PARTITION BY col_smallint) as field2 FROM td where col_smallint = -23828;").Sort().Check(testkit.Rows("4.0000"))
 	tk.MustExec("drop table td;")
 }

executor/builder.go

@@ -3719,7 +3719,7 @@ func (b *executorBuilder) buildWindow(v *plannercore.PhysicalWindow) *WindowExec
 	partialResults := make([]aggfuncs.PartialResult, 0, len(v.WindowFuncDescs))
 	resultColIdx := v.Schema().Len() - len(v.WindowFuncDescs)
 	for _, desc := range v.WindowFuncDescs {
-		aggDesc, err := aggregation.NewAggFuncDesc(b.ctx, desc.Name, desc.Args, false)
+		aggDesc, err := aggregation.NewAggFuncDescForWindowFunc(b.ctx, desc, false)
 		if err != nil {
 			b.err = err
 			return nil

executor/tiflash_test.go

@@ -588,6 +588,7 @@ func (s *tiflashTestSuite) TestAvgOverflow(c *C) {
 	tk.MustExec("set @@session.tidb_isolation_read_engines=\"tiflash\"")
 	tk.MustExec("set @@session.tidb_enforce_mpp=ON")
 	tk.MustQuery(" SELECT AVG( col_bigint / col_smallint) AS field1 FROM td;").Sort().Check(testkit.Rows("25769363061037.62077260"))
+	tk.MustQuery(" SELECT AVG(col_bigint) OVER (PARTITION BY col_smallint) as field2 FROM td where col_smallint = -23828;").Sort().Check(testkit.Rows("4.0000"))
 	tk.MustExec("drop table if exists td;")
 }
 

expression/aggregation/descriptor.go

@@ -41,6 +41,7 @@ type AggFuncDesc struct {
 }
 
 // NewAggFuncDesc creates an aggregation function signature descriptor.
+// this func cannot be called twice as the TypeInfer has changed the type of args in the first time.
 func NewAggFuncDesc(ctx sessionctx.Context, name string, args []expression.Expression, hasDistinct bool) (*AggFuncDesc, error) {
 	b, err := newBaseFuncDesc(ctx, name, args)
 	if err != nil {
@@ -49,6 +50,14 @@ func NewAggFuncDesc(ctx sessionctx.Context, name string, args []expression.Expre
 	return &AggFuncDesc{baseFuncDesc: b, HasDistinct: hasDistinct}, nil
 }
 
+// NewAggFuncDescForWindowFunc creates an aggregation function from window functions, where baseFuncDesc may be ready.
+func NewAggFuncDescForWindowFunc(ctx sessionctx.Context, Desc *WindowFuncDesc, hasDistinct bool) (*AggFuncDesc, error) {
+	if Desc.RetTp == nil { // safety check
+		return NewAggFuncDesc(ctx, Desc.Name, Desc.Args, hasDistinct)
+	}
+	return &AggFuncDesc{baseFuncDesc: baseFuncDesc{Desc.Name, Desc.Args, Desc.RetTp}, HasDistinct: hasDistinct}, nil
+}
+
 // String implements the fmt.Stringer interface.
 func (a *AggFuncDesc) String() string {
 	buffer := bytes.NewBufferString(a.Name)