Merge pull request #857 from jordanlewis/float32

encode: use 64-bit parsing for float32s

conn_test.go

@@ -1127,10 +1127,11 @@ func TestReadFloatPrecision(t *testing.T) {
 	db := openTestConn(t)
 	defer db.Close()
 
-	row := db.QueryRow("SELECT float4 '0.10000122', float8 '35.03554004971999'")
+	row := db.QueryRow("SELECT float4 '0.10000122', float8 '35.03554004971999', float4 '1.2'")
 	var float4val float32
 	var float8val float64
-	err := row.Scan(&float4val, &float8val)
+	var float4val2 float64
+	err := row.Scan(&float4val, &float8val, &float4val2)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1140,6 +1141,9 @@ func TestReadFloatPrecision(t *testing.T) {
 	if float8val != float64(35.03554004971999) {
 		t.Errorf("Expected float8 fidelity to be maintained; got no match")
 	}
+	if float4val2 != float64(1.2) {
+		t.Errorf("Expected float4 fidelity into a float64 to be maintained; got no match")
+	}
 }
 
 func TestXactMultiStmt(t *testing.T) {

encode.go

@@ -117,11 +117,10 @@ func textDecode(parameterStatus *parameterStatus, s []byte, typ oid.Oid) interfa
 		}
 		return i
 	case oid.T_float4, oid.T_float8:
-		bits := 64
-		if typ == oid.T_float4 {
-			bits = 32
-		}
-		f, err := strconv.ParseFloat(string(s), bits)
+		// We always use 64 bit parsing, regardless of whether the input text is for
+		// a float4 or float8, because clients expect float64s for all float datatypes
+		// and returning a 32-bit parsed float64 produces lossy results.
+		f, err := strconv.ParseFloat(string(s), 64)
 		if err != nil {
 			errorf("%s", err)
 		}