implement last_days() (#2460)

enginetest/queries/queries.go

@@ -9611,6 +9611,18 @@ from typestable`,
 			{time.Date(2024, 4, 15, 0, 0, 0, 0, time.UTC)},
 		},
 	},
+	{
+		Query: "select last_day('2000-02-21');",
+		Expected: []sql.Row{
+			{time.Date(2000, 2, 29, 0, 0, 0, 0, time.UTC)},
+		},
+	},
+	{
+		Query: "select last_day('1999-11-05');",
+		Expected: []sql.Row{
+			{time.Date(1999, 11, 30, 0, 0, 0, 0, time.UTC)},
+		},
+	},
 }
 
 var KeylessQueries = []QueryTest{

sql/expression/function/days.go

@@ -232,3 +232,82 @@ func (f *FromDays) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
 	months, days := daysToMonth(years, days)
 	return time.Date(int(years), time.Month(months), int(days), 0, 0, 0, 0, time.UTC), nil
 }
+
+// LastDay is a function that returns the date at the last day of the month.
+type LastDay struct {
+	expression.UnaryExpression
+}
+
+var _ sql.FunctionExpression = (*LastDay)(nil)
+var _ sql.CollationCoercible = (*LastDay)(nil)
+
+// NewLastDay creates a new LastDay function.
+func NewLastDay(date sql.Expression) sql.Expression {
+	return &LastDay{expression.UnaryExpression{Child: date}}
+}
+
+// CollationCoercibility implements sql.CollationCoercible
+func (f *LastDay) CollationCoercibility(ctx *sql.Context) (collation sql.CollationID, coercibility byte) {
+	return sql.Collation_binary, 5
+}
+
+// String implements sql.Stringer
+func (f *LastDay) String() string {
+	return fmt.Sprintf("%s(%s)", f.FunctionName(), f.Child.String())
+}
+
+// FunctionName implements sql.FunctionExpression
+func (f *LastDay) FunctionName() string {
+	return "last_day"
+}
+
+// Description implements sql.FunctionExpression
+func (f *LastDay) Description() string {
+	return "return the last day of the month for date"
+}
+
+// Type implements sql.Expression
+func (f *LastDay) Type() sql.Type {
+	return types.Date
+}
+
+// WithChildren implements sql.Expression
+func (f *LastDay) WithChildren(children ...sql.Expression) (sql.Expression, error) {
+	if len(children) != 1 {
+		return nil, sql.ErrInvalidChildrenNumber.New(f, len(children), 1)
+	}
+	return NewLastDay(children[0]), nil
+}
+
+// lastDay returns the last day of the month for the given year and month
+func lastDay(year, month int) int {
+	if month == 2 && isLeapYear(int64(year)) {
+		return 29
+	}
+	return int(daysPerMonth[month-1])
+}
+
+// Eval implements sql.Expression
+func (f *LastDay) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
+	date, err := f.Child.Eval(ctx, row)
+	if err != nil {
+		return nil, err
+	}
+	if date == nil {
+		return nil, nil
+	}
+
+	date, _, err = types.Date.Convert(date)
+	if err != nil {
+		ctx.Warn(1292, err.Error())
+		return nil, nil
+	}
+
+	d, ok := date.(time.Time)
+	if !ok {
+		return nil, nil
+	}
+
+	lDay := lastDay(d.Year(), int(d.Month()))
+	return time.Date(d.Year(), d.Month(), lDay, 0, 0, 0, 0, time.UTC), nil
+}

sql/expression/function/days_test.go

@@ -264,3 +264,110 @@ func TestFromDays(t *testing.T) {
 		})
 	}
 }
+
+func TestLastDay(t *testing.T) {
+	tests := []struct {
+		arg  sql.Expression
+		exp  interface{}
+		err  bool
+		skip bool
+	}{
+		{
+			arg: expression.NewLiteral(nil, types.Null),
+			exp: nil,
+		},
+		{
+			arg: expression.NewLiteral("notadate", types.Text),
+			exp: nil,
+		},
+		{
+			arg: expression.NewLiteral(-10, types.Int32),
+			exp: nil,
+		},
+		{
+			arg: expression.NewLiteral(366.13, types.Float32),
+			exp: nil,
+		},
+		{
+			arg: expression.NewLiteral("0004-02-01", types.Text),
+			exp: time.Date(4, 2, 29, 0, 0, 0, 0, time.UTC),
+		},
+		{
+			skip: true, // we should parse 00 days
+			arg:  expression.NewLiteral("0001-11-00", types.Text),
+			exp:  time.Date(1, 11, 30, 0, 0, 0, 0, time.UTC),
+		},
+		{
+			arg: expression.NewLiteral("2001-02-30", types.Text),
+			exp: nil,
+		},
+		{
+			arg: expression.NewLiteral("0001-01-31", types.Text),
+			exp: time.Date(1, 1, 31, 0, 0, 0, 0, time.UTC),
+		},
+
+		{
+			arg: expression.NewLiteral("0001-01-01", types.Text),
+			exp: time.Date(1, 1, 31, 0, 0, 0, 0, time.UTC),
+		},
+		{
+			arg: expression.NewLiteral("0001-02-01", types.Text),
+			exp: time.Date(1, 2, 28, 0, 0, 0, 0, time.UTC),
+		},
+		{
+			arg: expression.NewLiteral("0001-03-01", types.Text),
+			exp: time.Date(1, 3, 31, 0, 0, 0, 0, time.UTC),
+		},
+		{
+			arg: expression.NewLiteral("0001-04-01", types.Text),
+			exp: time.Date(1, 4, 30, 0, 0, 0, 0, time.UTC),
+		},
+		{
+			arg: expression.NewLiteral("0001-05-01", types.Text),
+			exp: time.Date(1, 5, 31, 0, 0, 0, 0, time.UTC),
+		},
+		{
+			arg: expression.NewLiteral("0001-06-01", types.Text),
+			exp: time.Date(1, 6, 30, 0, 0, 0, 0, time.UTC),
+		},
+		{
+			arg: expression.NewLiteral("0001-07-01", types.Text),
+			exp: time.Date(1, 7, 31, 0, 0, 0, 0, time.UTC),
+		},
+		{
+			arg: expression.NewLiteral("0001-08-01", types.Text),
+			exp: time.Date(1, 8, 31, 0, 0, 0, 0, time.UTC),
+		},
+		{
+			arg: expression.NewLiteral("0001-09-01", types.Text),
+			exp: time.Date(1, 9, 30, 0, 0, 0, 0, time.UTC),
+		},
+		{
+			arg: expression.NewLiteral("0001-10-01", types.Text),
+			exp: time.Date(1, 10, 31, 0, 0, 0, 0, time.UTC),
+		},
+		{
+			arg: expression.NewLiteral("0001-11-01", types.Text),
+			exp: time.Date(1, 11, 30, 0, 0, 0, 0, time.UTC),
+		},
+		{
+			arg: expression.NewLiteral("0001-12-01", types.Text),
+			exp: time.Date(1, 12, 31, 0, 0, 0, 0, time.UTC),
+		},
+	}
+	for _, tt := range tests {
+		name := fmt.Sprintf("last_day(%v)", tt.arg)
+		t.Run(name, func(t *testing.T) {
+			if tt.skip {
+				t.Skip()
+			}
+			f := NewLastDay(tt.arg)
+			res, err := f.Eval(sql.NewEmptyContext(), nil)
+			if tt.err {
+				require.Error(t, err)
+				return
+			}
+			require.Equal(t, tt.exp, res)
+		})
+	}
+}

sql/expression/function/registry.go

@@ -149,6 +149,7 @@ var BuiltIns = []sql.Function{
 	sql.FunctionN{Name: "json_value", Fn: json.NewJsonValue},
 	sql.FunctionN{Name: "lag", Fn: func(e ...sql.Expression) (sql.Expression, error) { return window.NewLag(e...) }},
 	sql.Function1{Name: "last", Fn: func(e sql.Expression) sql.Expression { return aggregation.NewLast(e) }},
+	sql.Function1{Name: "last_day", Fn: NewLastDay},
 	sql.FunctionN{Name: "last_insert_id", Fn: NewLastInsertId},
 	sql.FunctionN{Name: "last_insert_uuid", Fn: NewLastInsertUuid},
 	sql.Function1{Name: "lcase", Fn: NewLower},