Merge pull request #306 from pingcap/siddontang/decimal-scientific-notation

mysqldef: support parsing scientific notation

mysqldef/decimal.go

@@ -199,17 +199,28 @@ func NewDecimalFromUint(value uint64, exp int32) Decimal {
 //
 func ParseDecimal(value string) (Decimal, error) {
 	var intString string
-	var exp int32
+	var exp = int32(0)
+
+	n := strings.IndexAny(value, "eE")
+	if n > 0 {
+		// It is scientific notation, like 3.14e10
+		expInt, err := strconv.Atoi(value[n+1:])
+		if err != nil {
+			return Decimal{}, fmt.Errorf("can't convert %s to decimal, incorrect exponent", value)
+		}
+		value = value[0:n]
+		exp = int32(expInt)
+	}
+
 	parts := strings.Split(value, ".")
 	if len(parts) == 1 {
 		// There is no decimal point, we can just parse the original string as
 		// an int.
 		intString = value
-		exp = 0
 	} else if len(parts) == 2 {
 		intString = parts[0] + parts[1]
 		expInt := -len(parts[1])
-		exp = int32(expInt)
+		exp += int32(expInt)
 	} else {
 		return Decimal{}, fmt.Errorf("can't convert %s to decimal: too many .s", value)
 	}

mysqldef/decimal_test.go

@@ -869,3 +869,43 @@ func didPanic(f func()) bool {
 
 	return ret
 }
+
+func TestDecimalScientificNotation(t *testing.T) {
+	tbl := []struct {
+		Input    string
+		Expected float64
+	}{
+		{"314e-2", 3.14},
+		{"1e2", 100},
+		{"2E-1", 0.2},
+		{"2E0", 2},
+		{"2.2E-1", 0.22},
+	}
+
+	for _, c := range tbl {
+		n, err := ParseDecimal(c.Input)
+		if err != nil {
+			t.Error(err)
+		}
+
+		f, _ := n.Float64()
+		if f != c.Expected {
+			t.Errorf("%f != %f", f, c.Expected)
+		}
+	}
+
+	tblErr := []string{
+		"12ee",
+		"ae10",
+		"12e1a",
+		"12e1.2",
+		"e1",
+	}
+
+	for _, c := range tblErr {
+		_, err := ParseDecimal(c)
+		if err == nil {
+			t.Errorf("%s must be invalid decimal", c)
+		}
+	}
+}