Simplify []byte scanning

doc.go

@@ -169,10 +169,7 @@ and database/sql/driver.Valuer interfaces.
 Raw Bytes Mapping
 
 []byte passed as arguments to Query, QueryRow, and Exec are passed unmodified
-to PostgreSQL. In like manner, a *[]byte passed to Scan will be filled with
-the raw bytes returned by PostgreSQL. This can be especially useful for reading
-varchar, text, json, and jsonb values directly into a []byte and avoiding the
-type conversion from string.
+to PostgreSQL.
 
 Transactions
 

pgtype/text.go

@@ -49,6 +49,16 @@ func (src *Text) AssignTo(dst interface{}) error {
 			return fmt.Errorf("cannot assign %v to %T", src, dst)
 		}
 		*v = src.String
+	case *[]byte:
+		switch src.Status {
+		case Present:
+			*v = make([]byte, len(src.String))
+			copy(*v, src.String)
+		case Null:
+			*v = nil
+		default:
+			return fmt.Errorf("unknown status")
+		}
 	default:
 		if v := reflect.ValueOf(dst); v.Kind() == reflect.Ptr {
 			el := v.Elem()

pgtype/text_test.go

@@ -1,6 +1,7 @@
 package pgtype_test
 
 import (
+	"bytes"
 	"reflect"
 	"testing"
 
@@ -44,7 +45,7 @@ func TestTextAssignTo(t *testing.T) {
 	var s string
 	var ps *string
 
-	simpleTests := []struct {
+	stringTests := []struct {
 		src      pgtype.Text
 		dst      interface{}
 		expected interface{}
@@ -53,7 +54,7 @@ func TestTextAssignTo(t *testing.T) {
 		{src: pgtype.Text{Status: pgtype.Null}, dst: &ps, expected: ((*string)(nil))},
 	}
 
-	for i, tt := range simpleTests {
+	for i, tt := range stringTests {
 		err := tt.src.AssignTo(tt.dst)
 		if err != nil {
 			t.Errorf("%d: %v", i, err)
@@ -64,6 +65,28 @@ func TestTextAssignTo(t *testing.T) {
 		}
 	}
 
+	var buf []byte
+
+	bytesTests := []struct {
+		src      pgtype.Text
+		dst      *[]byte
+		expected []byte
+	}{
+		{src: pgtype.Text{String: "foo", Status: pgtype.Present}, dst: &buf, expected: []byte("foo")},
+		{src: pgtype.Text{Status: pgtype.Null}, dst: &buf, expected: nil},
+	}
+
+	for i, tt := range bytesTests {
+		err := tt.src.AssignTo(tt.dst)
+		if err != nil {
+			t.Errorf("%d: %v", i, err)
+		}
+
+		if bytes.Compare(*tt.dst, tt.expected) != 0 {
+			t.Errorf("%d: expected %v to assign %v, but result was %v", i, tt.src, tt.expected, tt.dst)
+		}
+	}
+
 	pointerAllocTests := []struct {
 		src      pgtype.Text
 		dst      interface{}

query.go

@@ -198,20 +198,7 @@ func (rows *Rows) Scan(dest ...interface{}) (err error) {
 			continue
 		}
 
-		// Check for []byte first as we allow sidestepping the decoding process and retrieving the raw bytes
-		if b, ok := d.(*[]byte); ok {
-			// If it actually is a bytea then pass it through decodeBytea (so it can be decoded if it is in text format)
-			// Otherwise read the bytes directly regardless of what the actual type is.
-			if vr.Type().DataType == ByteaOid {
-				*b = decodeBytea(vr)
-			} else {
-				if vr.Len() != -1 {
-					*b = vr.ReadBytes(vr.Len())
-				} else {
-					*b = nil
-				}
-			}
-		} else if s, ok := d.(pgtype.BinaryDecoder); ok && vr.Type().FormatCode == BinaryFormatCode {
+		if s, ok := d.(pgtype.BinaryDecoder); ok && vr.Type().FormatCode == BinaryFormatCode {
 			err = s.DecodeBinary(rows.conn.ConnInfo, vr.bytes())
 			if err != nil {
 				rows.Fatal(scanArgError{col: i, err: err})

query_test.go

@@ -684,7 +684,6 @@ func TestQueryRowCoreByteSlice(t *testing.T) {
 	}{
 		{"select $1::text", "Jack", []byte("Jack")},
 		{"select $1::text", []byte("Jack"), []byte("Jack")},
-		{"select $1::int4", int32(239023409), []byte{14, 63, 53, 49}},
 		{"select $1::varchar", []byte("Jack"), []byte("Jack")},
 		{"select $1::bytea", []byte{0, 15, 255, 17}, []byte{0, 15, 255, 17}},
 	}

v3.md

@@ -28,6 +28,8 @@ Reject scanning binary format values into a string (e.g. binary encoded timestam
 
 Remove CopyTo
 
+No longer can read raw bytes of any value into a []byte. Use pgtype.GenericBinary if this functionality is needed.
+
 ## TODO / Possible / Investigate
 
 Organize errors better

values.go

@@ -217,21 +217,3 @@ func stripNamedType(val *reflect.Value) (interface{}, bool) {
 
 	return nil, false
 }
-
-func decodeBytea(vr *ValueReader) []byte {
-	if vr.Len() == -1 {
-		return nil
-	}
-
-	if vr.Type().DataType != ByteaOid {
-		vr.Fatal(ProtocolError(fmt.Sprintf("Cannot decode oid %v into []byte", vr.Type().DataType)))
-		return nil
-	}
-
-	if vr.Type().FormatCode != BinaryFormatCode {
-		vr.Fatal(ProtocolError(fmt.Sprintf("Unknown field description format code: %v", vr.Type().FormatCode)))
-		return nil
-	}
-
-	return vr.ReadBytes(vr.Len())
-}