Merge branch 'record-expect' of git://github.com/redbaron/pgtype into redbaron-record-expect

.vscode/settings.json

@@ -0,0 +1,6 @@
+{
+    "go.inferGopath": false,
+    "go.testEnvVars": {
+       "PGX_TEST_DATABASE": "user=postgres database=pgx_test host=127.0.0.1"
+    },
+}

binary/record.go

@@ -0,0 +1,78 @@
+package binary
+
+import (
+	"encoding/binary"
+
+	"github.com/jackc/pgio"
+	errors "golang.org/x/xerrors"
+)
+
+type RecordFieldIter struct {
+	rp  int
+	src []byte
+}
+
+// NewRecordFieldIterator creates iterator over binary representation
+// of record, aka ROW(), aka Composite
+func NewRecordFieldIterator(src []byte) (RecordFieldIter, int, error) {
+	rp := 0
+	if len(src[rp:]) < 4 {
+		return RecordFieldIter{}, 0, errors.Errorf("Record incomplete %v", src)
+	}
+
+	fieldCount := int(int32(binary.BigEndian.Uint32(src[rp:])))
+	rp += 4
+
+	return RecordFieldIter{
+		rp:  rp,
+		src: src,
+	}, fieldCount, nil
+}
+
+// Next returns next field decoded from record. eof is returned if no
+// more fields left to decode.
+func (fi *RecordFieldIter) Next() (fieldOID uint32, buf []byte, eof bool, err error) {
+	if fi.rp == len(fi.src) {
+		eof = true
+		return
+	}
+
+	if len(fi.src[fi.rp:]) < 8 {
+		err = errors.Errorf("Record incomplete %v", fi.src)
+		return
+	}
+	fieldOID = binary.BigEndian.Uint32(fi.src[fi.rp:])
+	fi.rp += 4
+
+	fieldLen := int(int32(binary.BigEndian.Uint32(fi.src[fi.rp:])))
+	fi.rp += 4
+
+	if fieldLen >= 0 {
+		if len(fi.src[fi.rp:]) < fieldLen {
+			err = errors.Errorf("Record incomplete rp=%d src=%v", fi.rp, fi.src)
+			return
+		}
+		buf = fi.src[fi.rp : fi.rp+fieldLen]
+		fi.rp += fieldLen
+	}
+
+	return
+}
+
+// RecordStart adds record header to the buf
+func RecordStart(buf []byte, fieldCount int) []byte {
+	return pgio.AppendUint32(buf, uint32(fieldCount))
+}
+
+// RecordAdd adds record field to the buf
+func RecordAdd(buf []byte, oid uint32, fieldBytes []byte) []byte {
+	buf = pgio.AppendUint32(buf, oid)
+	buf = pgio.AppendUint32(buf, uint32(len(fieldBytes)))
+	buf = append(buf, fieldBytes...)
+	return buf
+}
+
+// RecordAddNull adds null value as a field to the buf
+func RecordAddNull(buf []byte, oid uint32) []byte {
+	return pgio.AppendInt32(buf, int32(-1))
+}

composite.go

@@ -0,0 +1,153 @@
+package pgtype
+
+import (
+	"github.com/jackc/pgtype/binary"
+	errors "golang.org/x/xerrors"
+)
+
+type Composite struct {
+	fields []Value
+	Status Status
+}
+
+// NewComposite creates a Composite object, which acts as a "schema" for
+// SQL composite values.
+// To pass Composite as SQL parameter first set it's fields, either by
+// passing initialized Value{} instances to NewComposite or by calling
+// SetFields method
+// To read composite fields back pass result of Scan() method
+// to query Scan function.
+func NewComposite(fields ...Value) *Composite {
+	return &Composite{fields, Present}
+}
+
+func (src Composite) Get() interface{} {
+	switch src.Status {
+	case Present:
+		return src
+	case Null:
+		return nil
+	default:
+		return src.Status
+	}
+}
+
+// Set is called internally when passing query arguments.
+func (dst *Composite) Set(src interface{}) error {
+	if src == nil {
+		*dst = Composite{Status: Null}
+		return nil
+	}
+
+	switch value := src.(type) {
+	case []Value:
+		if len(value) != len(dst.fields) {
+			return errors.Errorf("Number of fields don't match. Composite has %d fields", len(dst.fields))
+		}
+		for i, v := range value {
+			if err := dst.fields[i].Set(v); err != nil {
+				return err
+			}
+		}
+		dst.Status = Present
+	default:
+		return errors.Errorf("Can not convert %v to Composite", src)
+	}
+
+	return nil
+}
+
+// AssignTo should never be called on composite value directly
+func (src Composite) AssignTo(dst interface{}) error {
+	return errors.New("Pass Composite.Scan() to deconstruct composite")
+}
+
+func (src Composite) EncodeBinary(ci *ConnInfo, buf []byte) (newBuf []byte, err error) {
+	switch src.Status {
+	case Null:
+		return nil, nil
+	case Undefined:
+		return nil, errUndefined
+	}
+	return EncodeRow(ci, buf, src.fields...)
+}
+
+// DecodeBinary implements BinaryDecoder interface.
+// Opposite to Record, fields in a composite act as a "schema"
+// and decoding fails if SQL value can't be assigned due to
+// type mismatch
+func (dst *Composite) DecodeBinary(ci *ConnInfo, buf []byte) (err error) {
+	if buf == nil {
+		dst.Status = Null
+		return nil
+	}
+
+	fieldIter, fieldCount, err := binary.NewRecordFieldIterator(buf)
+	if err != nil {
+		return err
+	} else if len(dst.fields) != fieldCount {
+		return errors.Errorf("SQL composite can't be read, field count mismatch. expected %d , found %d", len(dst.fields), fieldCount)
+	}
+
+	_, fieldBytes, eof, err := fieldIter.Next()
+
+	for i := 0; !eof; i++ {
+		if err != nil {
+			return err
+		}
+
+		binaryDecoder, ok := dst.fields[i].(BinaryDecoder)
+		if !ok {
+			return errors.New("Composite field doesn't support binary protocol")
+		}
+
+		if err = binaryDecoder.DecodeBinary(ci, fieldBytes); err != nil {
+			return err
+		}
+
+		_, fieldBytes, eof, err = fieldIter.Next()
+	}
+	dst.Status = Present
+
+	return nil
+}
+
+// Scan is a helper function to perform "nested" scan of
+// a composite value when scanning a query result row.
+// isNull is set if scanned value is NULL
+// Rest of arguments are set in the order of fields in the composite
+//
+// Use of Scan method doesn't modify original composite
+func (src Composite) Scan(isNull *bool, dst ...interface{}) BinaryDecoderFunc {
+	return func(ci *ConnInfo, buf []byte) error {
+		if err := src.DecodeBinary(ci, buf); err != nil {
+			return err
+		}
+
+		if src.Status == Null {
+			*isNull = true
+			return nil
+		}
+
+		for i, f := range src.fields {
+			if err := f.AssignTo(dst[i]); err != nil {
+				return err
+			}
+		}
+		return nil
+	}
+}
+
+// SetFields sets Composite's fields to corresponding values
+func (dst *Composite) SetFields(values ...interface{}) error {
+	if len(values) != len(dst.fields) {
+		return errors.Errorf("Number of fields don't match. Composite has %d fields", len(dst.fields))
+	}
+	for i, v := range values {
+		if err := dst.fields[i].Set(v); err != nil {
+			return err
+		}
+	}
+	dst.Status = Present
+	return nil
+}

composite_bench_test.go

@@ -0,0 +1,196 @@
+package pgtype_test
+
+import (
+	"testing"
+
+	"github.com/jackc/pgtype"
+	"github.com/jackc/pgtype/binary"
+	errors "golang.org/x/xerrors"
+)
+
+type MyCompositeRaw struct {
+	A int32
+	B *string
+}
+
+func (src MyCompositeRaw) EncodeBinary(ci *pgtype.ConnInfo, buf []byte) (newBuf []byte, err error) {
+	a := pgtype.Int4{src.A, pgtype.Present}
+
+	fieldBytes := make([]byte, 0, 64)
+	fieldBytes, _ = a.EncodeBinary(ci, fieldBytes[:0])
+
+	newBuf = binary.RecordStart(buf, 2)
+	newBuf = binary.RecordAdd(newBuf, pgtype.Int4OID, fieldBytes)
+
+	if src.B != nil {
+		fieldBytes, _ = pgtype.Text{*src.B, pgtype.Present}.EncodeBinary(ci, fieldBytes[:0])
+		newBuf = binary.RecordAdd(newBuf, pgtype.TextOID, fieldBytes)
+	} else {
+		newBuf = binary.RecordAddNull(newBuf, pgtype.TextOID)
+	}
+	return
+}
+
+func (dst *MyCompositeRaw) DecodeBinary(ci *pgtype.ConnInfo, src []byte) error {
+	a := pgtype.Int4{}
+	b := pgtype.Text{}
+
+	fieldIter, fieldCount, err := binary.NewRecordFieldIterator(src)
+	if err != nil {
+		return err
+	}
+
+	if 2 != fieldCount {
+		return errors.Errorf("can't scan row value, number of fields don't match: found=%d expected=2", fieldCount)
+	}
+
+	_, fieldBytes, eof, err := fieldIter.Next()
+	if eof || err != nil {
+		return errors.New("Bad record")
+	}
+	if err = a.DecodeBinary(ci, fieldBytes); err != nil {
+		return err
+	}
+
+	_, fieldBytes, eof, err = fieldIter.Next()
+	if eof || err != nil {
+		return errors.New("Bad record")
+	}
+	if err = b.DecodeBinary(ci, fieldBytes); err != nil {
+		return err
+	}
+
+	dst.A = a.Int
+	if b.Status == pgtype.Present {
+		dst.B = &b.String
+	} else {
+		dst.B = nil
+	}
+
+	return nil
+}
+
+var x []byte
+
+func BenchmarkBinaryEncodingManual(b *testing.B) {
+	buf := make([]byte, 0, 128)
+	ci := pgtype.NewConnInfo()
+	v := MyCompositeRaw{4, ptrS("ABCDEFG")}
+
+	b.ResetTimer()
+	for n := 0; n < b.N; n++ {
+		buf, _ = v.EncodeBinary(ci, buf[:0])
+	}
+	x = buf
+}
+
+func BenchmarkBinaryEncodingHelper(b *testing.B) {
+	buf := make([]byte, 0, 128)
+	ci := pgtype.NewConnInfo()
+	v := MyType{4, ptrS("ABCDEFG")}
+
+	b.ResetTimer()
+	for n := 0; n < b.N; n++ {
+		buf, _ = v.EncodeBinary(ci, buf[:0])
+	}
+	x = buf
+}
+
+func BenchmarkBinaryEncodingComposite(b *testing.B) {
+	buf := make([]byte, 0, 128)
+	ci := pgtype.NewConnInfo()
+	f1 := 2
+	f2 := ptrS("bar")
+	c := pgtype.NewComposite(&pgtype.Int4{}, &pgtype.Text{})
+
+	b.ResetTimer()
+	for n := 0; n < b.N; n++ {
+		c.SetFields(f1, f2)
+		buf, _ = c.EncodeBinary(ci, buf[:0])
+	}
+	x = buf
+}
+
+func BenchmarkBinaryEncodingJSON(b *testing.B) {
+	buf := make([]byte, 0, 128)
+	ci := pgtype.NewConnInfo()
+	v := MyCompositeRaw{4, ptrS("ABCDEFG")}
+	j := pgtype.JSON{}
+
+	b.ResetTimer()
+	for n := 0; n < b.N; n++ {
+		j.Set(v)
+		buf, _ = j.EncodeBinary(ci, buf[:0])
+	}
+	x = buf
+}
+
+var dstRaw MyCompositeRaw
+
+func BenchmarkBinaryDecodingManual(b *testing.B) {
+	ci := pgtype.NewConnInfo()
+	buf, _ := MyType{4, ptrS("ABCDEFG")}.EncodeBinary(ci, nil)
+	dst := MyCompositeRaw{}
+
+	b.ResetTimer()
+	for n := 0; n < b.N; n++ {
+		err := dst.DecodeBinary(ci, buf)
+		E(err)
+	}
+	dstRaw = dst
+}
+
+var dstMyType MyType
+
+func BenchmarkBinaryDecodingHelpers(b *testing.B) {
+	ci := pgtype.NewConnInfo()
+	buf, _ := MyType{4, ptrS("ABCDEFG")}.EncodeBinary(ci, nil)
+	dst := MyType{}
+
+	b.ResetTimer()
+	for n := 0; n < b.N; n++ {
+		err := dst.DecodeBinary(ci, buf)
+		E(err)
+	}
+	dstMyType = dst
+}
+
+var gf1 int
+var gf2 *string
+
+func BenchmarkBinaryDecodingCompositeScan(b *testing.B) {
+	ci := pgtype.NewConnInfo()
+	buf, _ := MyType{4, ptrS("ABCDEFG")}.EncodeBinary(ci, nil)
+	var isNull bool
+	var f1 int
+	var f2 *string
+
+	c := pgtype.NewComposite(&pgtype.Int4{}, &pgtype.Text{})
+
+	b.ResetTimer()
+	for n := 0; n < b.N; n++ {
+		err := c.Scan(&isNull, &f1, &f2).DecodeBinary(ci, buf)
+		E(err)
+	}
+	gf1 = f1
+	gf2 = f2
+}
+
+func BenchmarkBinaryDecodingJSON(b *testing.B) {
+	ci := pgtype.NewConnInfo()
+	j := pgtype.JSON{}
+	j.Set(MyCompositeRaw{4, ptrS("ABCDEFG")})
+	buf, _ := j.EncodeBinary(ci, nil)
+
+	j = pgtype.JSON{}
+	dst := MyCompositeRaw{}
+
+	b.ResetTimer()
+	for n := 0; n < b.N; n++ {
+		err := j.DecodeBinary(ci, buf)
+		E(err)
+		err = j.AssignTo(&dst)
+		E(err)
+	}
+	dstRaw = dst
+}

composite_test.go

@@ -0,0 +1,57 @@
+package pgtype_test
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"github.com/jackc/pgtype"
+	pgx "github.com/jackc/pgx/v4"
+)
+
+//ExampleComposite demonstrates use of Row() function to pass and receive
+// back composite types without creating boilderplate custom types.
+func Example_composite() {
+	conn, err := pgx.Connect(context.Background(), os.Getenv("PGX_TEST_DATABASE"))
+	E(err)
+
+	defer conn.Close(context.Background())
+	_, err = conn.Exec(context.Background(), `drop type if exists mytype;
+
+create type mytype as (
+  a int4,
+  b text
+);`)
+	E(err)
+	defer conn.Exec(context.Background(), "drop type mytype")
+
+	qrf := pgx.QueryResultFormats{pgx.BinaryFormatCode}
+
+	var isNull bool
+	var a int
+	var b *string
+
+	c := pgtype.NewComposite(&pgtype.Int4{}, &pgtype.Text{})
+	c.SetFields(2, "bar")
+
+	err = conn.QueryRow(context.Background(), "select $1::mytype", qrf, c).
+		Scan(c.Scan(&isNull, &a, &b))
+	E(err)
+
+	fmt.Printf("First: isNull=%v a=%d b=%s\n", isNull, a, *b)
+
+	err = conn.QueryRow(context.Background(), "select (1, NULL)::mytype", qrf).Scan(c.Scan(&isNull, &a, &b))
+	E(err)
+
+	fmt.Printf("Second: isNull=%v a=%d b=%v\n", isNull, a, b)
+
+	err = conn.QueryRow(context.Background(), "select NULL::mytype", qrf).Scan(c.Scan(&isNull, &a, &b))
+	E(err)
+
+	fmt.Printf("Third: isNull=%v\n", isNull)
+
+	// Output:
+	// First: isNull=false a=2 b=bar
+	// Second: isNull=false a=1 b=<nil>
+	// Third: isNull=true
+}

convert.go

@@ -5,6 +5,7 @@ import (
 	"reflect"
 	"time"
 
+	"github.com/jackc/pgtype/binary"
 	errors "golang.org/x/xerrors"
 )
 
@@ -433,6 +434,68 @@ func GetAssignToDstType(dst interface{}) (interface{}, bool) {
 	return nil, false
 }
 
+// ScanRowValue decodes ROW()'s and composite type
+// from src argument using provided decoders. Decoders should match
+// order and count of fields of record being decoded.
+//
+// In practice you can pass pgtype.Value types as decoders, as
+// most of them implement BinaryDecoder interface.
+//
+// ScanRowValue takes ownership of src, caller MUST not use it after call
+func ScanRowValue(ci *ConnInfo, src []byte, dst ...BinaryDecoder) error {
+	fieldIter, fieldCount, err := binary.NewRecordFieldIterator(src)
+	if err != nil {
+		return err
+	}
+
+	if len(dst) != fieldCount {
+		return errors.Errorf("can't scan row value, number of fields don't match: found=%d expected=%d", fieldCount, len(dst))
+	}
+
+	_, fieldBytes, eof, err := fieldIter.Next()
+	for i := 0; !eof; i++ {
+		if err != nil {
+			return err
+		}
+
+		if err = dst[i].DecodeBinary(ci, fieldBytes); err != nil {
+			return err
+		}
+
+		_, fieldBytes, eof, err = fieldIter.Next()
+	}
+
+	return nil
+}
+
+// EncodeRow builds a binary representation of row values (row(), composite types)
+func EncodeRow(ci *ConnInfo, buf []byte, fields ...Value) (newBuf []byte, err error) {
+	fieldBytes := make([]byte, 0, 128)
+
+	newBuf = binary.RecordStart(buf, len(fields))
+	for _, f := range fields {
+		dt, ok := ci.DataTypeForValue(f)
+		if !ok {
+			return nil, errors.Errorf("Unknown OID for %s", f)
+		}
+		if f.Get() != nil {
+			binaryEncoder, ok := f.(BinaryEncoder)
+			if !ok {
+				return nil, errors.Errorf("record field doesn't implement binary encoding: %s", reflect.TypeOf(f).Name())
+			}
+			fieldBytes, err = binaryEncoder.EncodeBinary(ci, fieldBytes[:0])
+			if err != nil {
+				return nil, err
+			}
+			newBuf = binary.RecordAdd(newBuf, dt.OID, fieldBytes)
+		} else {
+			newBuf = binary.RecordAddNull(newBuf, dt.OID)
+		}
+
+	}
+	return
+}
+
 func init() {
 	kindTypes = map[reflect.Kind]reflect.Type{
 		reflect.Bool:    reflect.TypeOf(false),

custom_composite_test.go

@@ -0,0 +1,101 @@
+package pgtype_test
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"github.com/jackc/pgtype"
+	pgx "github.com/jackc/pgx/v4"
+	errors "golang.org/x/xerrors"
+)
+
+type MyType struct {
+	a int32   // NULL will cause decoding error
+	b *string // there can be NULL in this position in SQL
+}
+
+func (dst *MyType) DecodeBinary(ci *pgtype.ConnInfo, src []byte) error {
+	if src == nil {
+		return errors.New("NULL values can't be decoded. Scan into a &*MyType to handle NULLs")
+	}
+
+	a := pgtype.Int4{}
+	b := pgtype.Text{}
+
+	if err := pgtype.ScanRowValue(ci, src, &a, &b); err != nil {
+		return err
+	}
+
+	// type compatibility is checked by AssignTo
+	// only lossless assignments will succeed
+	if err := a.AssignTo(&dst.a); err != nil {
+		return err
+	}
+
+	// AssignTo also deals with null value handling
+	if err := b.AssignTo(&dst.b); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (src MyType) EncodeBinary(ci *pgtype.ConnInfo, buf []byte) (newBuf []byte, err error) {
+	a := pgtype.Int4{src.a, pgtype.Present}
+	var b pgtype.Text
+	if src.b != nil {
+		b = pgtype.Text{*src.b, pgtype.Present}
+	} else {
+		b = pgtype.Text{Status: pgtype.Null}
+	}
+
+	return pgtype.EncodeRow(ci, buf, &a, &b)
+}
+
+func ptrS(s string) *string {
+	return &s
+}
+
+func E(err error) {
+	if err != nil {
+		panic(err)
+	}
+}
+
+// ExampleCustomCompositeTypes demonstrates how support for custom types mappable to SQL
+// composites can be added.
+func Example_customCompositeTypes() {
+	conn, err := pgx.Connect(context.Background(), os.Getenv("PGX_TEST_DATABASE"))
+	E(err)
+
+	defer conn.Close(context.Background())
+	_, err = conn.Exec(context.Background(), `drop type if exists mytype;
+
+create type mytype as (
+  a int4,
+  b text
+);`)
+	E(err)
+	defer conn.Exec(context.Background(), "drop type mytype")
+
+	var result *MyType
+
+	// Demonstrates both passing and reading back composite values
+	err = conn.QueryRow(context.Background(), "select $1::mytype",
+		pgx.QueryResultFormats{pgx.BinaryFormatCode}, MyType{1, ptrS("foo")}).
+		Scan(&result)
+	E(err)
+
+	fmt.Printf("First row: a=%d b=%s\n", result.a, *result.b)
+
+	// Because we scan into &*MyType, NULLs are handled generically by assigning nil to result
+	err = conn.QueryRow(context.Background(), "select NULL::mytype", pgx.QueryResultFormats{pgx.BinaryFormatCode}).Scan(&result)
+	E(err)
+
+	fmt.Printf("Second row: %v\n", result)
+
+	// Output:
+	// First row: a=1 b=foo
+	// Second row: <nil>
+}

pgtype.go

@@ -174,6 +174,24 @@ type TextEncoder interface {
 	EncodeText(ci *ConnInfo, buf []byte) (newBuf []byte, err error)
 }
 
+//The BinaryDecoderFunc type is an adapter to allow the use of ordinary functions as BinaryDecoder types.
+// If f is a function with the appropriate signature, BinaryDecoderFunc(f) is a BinaryDecoder that calls f.
+type BinaryDecoderFunc func(ci *ConnInfo, src []byte) error
+
+// DecodeBinary calls f(ci, src)
+func (f BinaryDecoderFunc) DecodeBinary(ci *ConnInfo, src []byte) error {
+	return f(ci, src)
+}
+
+//The BinaryEncoderFunc type is an adapter to allow the use of ordinary functions as BinaryDecoder types.
+// If f is a function with the appropriate signature, BinaryEncoderFunc(f) is a BinaryDecoder that calls f.
+type BinaryEncoderFunc func(ci *ConnInfo, buf []byte) ([]byte, error)
+
+// EncodeBinary calls f(ci, buf)
+func (f BinaryEncoderFunc) EncodeBinary(ci *ConnInfo, buf []byte) (newBuf []byte, err error) {
+	return f(ci, buf)
+}
+
 var errUndefined = errors.New("cannot encode status undefined")
 var errBadStatus = errors.New("invalid status")
 

record.go

@@ -1,9 +1,10 @@
 package pgtype
 
 import (
-	"encoding/binary"
 	"reflect"
 
+	"github.com/jackc/pgtype/binary"
+
 	errors "golang.org/x/xerrors"
 )
 
@@ -78,57 +79,54 @@ func (src *Record) AssignTo(dst interface{}) error {
 	return errors.Errorf("cannot decode %#v into %T", src, dst)
 }
 
+func prepareNewBinaryDecoder(ci *ConnInfo, fieldOID uint32, v *Value) (BinaryDecoder, error) {
+	var binaryDecoder BinaryDecoder
+
+	if dt, ok := ci.DataTypeForOID(fieldOID); ok {
+		binaryDecoder, _ = dt.Value.(BinaryDecoder)
+	} else {
+		return nil, errors.Errorf("unknown oid while decoding record: %v", fieldOID)
+	}
+
+	if binaryDecoder == nil {
+		return nil, errors.Errorf("no binary decoder registered for: %v", fieldOID)
+	}
+
+	// Duplicate struct to scan into
+	binaryDecoder = reflect.New(reflect.ValueOf(binaryDecoder).Elem().Type()).Interface().(BinaryDecoder)
+	*v = binaryDecoder.(Value)
+	return binaryDecoder, nil
+}
+
 func (dst *Record) DecodeBinary(ci *ConnInfo, src []byte) error {
 	if src == nil {
 		*dst = Record{Status: Null}
 		return nil
 	}
 
-	rp := 0
-
-	if len(src[rp:]) < 4 {
-		return errors.Errorf("Record incomplete %v", src)
+	fieldIter, fieldCount, err := binary.NewRecordFieldIterator(src)
+	if err != nil {
+		return err
 	}
-	fieldCount := int(int32(binary.BigEndian.Uint32(src[rp:])))
-	rp += 4
 
 	fields := make([]Value, fieldCount)
+	fieldOID, fieldBytes, eof, err := fieldIter.Next()
 
-	for i := 0; i < fieldCount; i++ {
-		if len(src[rp:]) < 8 {
-			return errors.Errorf("Record incomplete %v", src)
-		}
-		fieldOID := binary.BigEndian.Uint32(src[rp:])
-		rp += 4
-
-		fieldLen := int(int32(binary.BigEndian.Uint32(src[rp:])))
-		rp += 4
-
-		var binaryDecoder BinaryDecoder
-		if dt, ok := ci.DataTypeForOID(fieldOID); ok {
-			binaryDecoder, _ = dt.Value.(BinaryDecoder)
-		}
-		if binaryDecoder == nil {
-			return errors.Errorf("unknown oid while decoding record: %v", fieldOID)
-		}
-
-		var fieldBytes []byte
-		if fieldLen >= 0 {
-			if len(src[rp:]) < fieldLen {
-				return errors.Errorf("Record incomplete %v", src)
-			}
-			fieldBytes = src[rp : rp+fieldLen]
-			rp += fieldLen
-		}
-
-		// Duplicate struct to scan into
-		binaryDecoder = reflect.New(reflect.ValueOf(binaryDecoder).Elem().Type()).Interface().(BinaryDecoder)
-
-		if err := binaryDecoder.DecodeBinary(ci, fieldBytes); err != nil {
+	for i := 0; !eof; i++ {
+		if err != nil {
 			return err
 		}
 
-		fields[i] = binaryDecoder.(Value)
+		binaryDecoder, err := prepareNewBinaryDecoder(ci, fieldOID, &fields[i])
+		if err != nil {
+			return err
+		}
+
+		if err = binaryDecoder.DecodeBinary(ci, fieldBytes); err != nil {
+			return err
+		}
+
+		fieldOID, fieldBytes, eof, err = fieldIter.Next()
 	}
 
 	*dst = Record{Fields: fields, Status: Present}

record_test.go

@@ -11,94 +11,145 @@ import (
 	"github.com/jackc/pgx/v4"
 )
 
+var recordTests = []struct {
+	sql      string
+	expected pgtype.Record
+}{
+	{
+		sql: `select row()`,
+		expected: pgtype.Record{
+			Fields: []pgtype.Value{},
+			Status: pgtype.Present,
+		},
+	},
+	{
+		sql: `select row('foo'::text, 42::int4)`,
+		expected: pgtype.Record{
+			Fields: []pgtype.Value{
+				&pgtype.Text{String: "foo", Status: pgtype.Present},
+				&pgtype.Int4{Int: 42, Status: pgtype.Present},
+			},
+			Status: pgtype.Present,
+		},
+	},
+	{
+		sql: `select row(100.0::float4, 1.09::float4)`,
+		expected: pgtype.Record{
+			Fields: []pgtype.Value{
+				&pgtype.Float4{Float: 100, Status: pgtype.Present},
+				&pgtype.Float4{Float: 1.09, Status: pgtype.Present},
+			},
+			Status: pgtype.Present,
+		},
+	},
+	{
+		sql: `select row('foo'::text, array[1, 2, null, 4]::int4[], 42::int4)`,
+		expected: pgtype.Record{
+			Fields: []pgtype.Value{
+				&pgtype.Text{String: "foo", Status: pgtype.Present},
+				&pgtype.Int4Array{
+					Elements: []pgtype.Int4{
+						{Int: 1, Status: pgtype.Present},
+						{Int: 2, Status: pgtype.Present},
+						{Status: pgtype.Null},
+						{Int: 4, Status: pgtype.Present},
+					},
+					Dimensions: []pgtype.ArrayDimension{{Length: 4, LowerBound: 1}},
+					Status:     pgtype.Present,
+				},
+				&pgtype.Int4{Int: 42, Status: pgtype.Present},
+			},
+			Status: pgtype.Present,
+		},
+	},
+	{
+		sql: `select row(null)`,
+		expected: pgtype.Record{
+			Fields: []pgtype.Value{
+				&pgtype.Unknown{Status: pgtype.Null},
+			},
+			Status: pgtype.Present,
+		},
+	},
+	{
+		sql: `select null::record`,
+		expected: pgtype.Record{
+			Status: pgtype.Null,
+		},
+	},
+}
+
+// row values are binary compatible with records, so we test our helper
+// routines here
+func TestScanRowValue(t *testing.T) {
+	conn := testutil.MustConnectPgx(t)
+	defer testutil.MustCloseContext(t, conn)
+
+	for i := 0; i < len(recordTests); i++ {
+		tt := recordTests[i]
+		psName := fmt.Sprintf("test%d", i)
+		_, err := conn.Prepare(context.Background(), psName, tt.sql)
+		if err != nil {
+			t.Fatal(err)
+		}
+		t.Run(tt.sql, func(t *testing.T) {
+			desc := []pgtype.BinaryDecoder{}
+			for _, f := range tt.expected.Fields {
+				desc = append(desc, f.(pgtype.BinaryDecoder))
+			}
+
+			var raw pgtype.GenericBinary
+
+			if err := conn.QueryRow(context.Background(), psName, pgx.QueryResultFormats{pgx.BinaryFormatCode}).Scan(&raw); err != nil {
+				t.Error(err)
+				return
+			}
+
+			if raw.Status == pgtype.Null {
+				// ScanRowValue deals with complete rows only, NULL values (but NOT null fields)
+				// should be handled by the calling code
+				return
+			}
+
+			if err := pgtype.ScanRowValue(conn.ConnInfo(), raw.Bytes, desc...); err != nil {
+				t.Error(err)
+			}
+
+			// borrow fields from a neighbor test, this makes scan always fail
+			desc = desc[:0]
+			for _, f := range recordTests[(i+1)%len(recordTests)].expected.Fields {
+				desc = append(desc, f.(pgtype.BinaryDecoder))
+			}
+			if err := pgtype.ScanRowValue(conn.ConnInfo(), raw.Bytes, desc...); err == nil {
+				t.Error("Matching scan didn't fail, despite fields not mathching query result")
+			}
+		})
+	}
+}
+
 func TestRecordTranscode(t *testing.T) {
 	conn := testutil.MustConnectPgx(t)
 	defer testutil.MustCloseContext(t, conn)
 
-	tests := []struct {
-		sql      string
-		expected pgtype.Record
-	}{
-		{
-			sql: `select row()`,
-			expected: pgtype.Record{
-				Fields: []pgtype.Value{},
-				Status: pgtype.Present,
-			},
-		},
-		{
-			sql: `select row('foo'::text, 42::int4)`,
-			expected: pgtype.Record{
-				Fields: []pgtype.Value{
-					&pgtype.Text{String: "foo", Status: pgtype.Present},
-					&pgtype.Int4{Int: 42, Status: pgtype.Present},
-				},
-				Status: pgtype.Present,
-			},
-		},
-		{
-			sql: `select row(100.0::float4, 1.09::float4)`,
-			expected: pgtype.Record{
-				Fields: []pgtype.Value{
-					&pgtype.Float4{Float: 100, Status: pgtype.Present},
-					&pgtype.Float4{Float: 1.09, Status: pgtype.Present},
-				},
-				Status: pgtype.Present,
-			},
-		},
-		{
-			sql: `select row('foo'::text, array[1, 2, null, 4]::int4[], 42::int4)`,
-			expected: pgtype.Record{
-				Fields: []pgtype.Value{
-					&pgtype.Text{String: "foo", Status: pgtype.Present},
-					&pgtype.Int4Array{
-						Elements: []pgtype.Int4{
-							{Int: 1, Status: pgtype.Present},
-							{Int: 2, Status: pgtype.Present},
-							{Status: pgtype.Null},
-							{Int: 4, Status: pgtype.Present},
-						},
-						Dimensions: []pgtype.ArrayDimension{{Length: 4, LowerBound: 1}},
-						Status:     pgtype.Present,
-					},
-					&pgtype.Int4{Int: 42, Status: pgtype.Present},
-				},
-				Status: pgtype.Present,
-			},
-		},
-		{
-			sql: `select row(null)`,
-			expected: pgtype.Record{
-				Fields: []pgtype.Value{
-					&pgtype.Unknown{Status: pgtype.Null},
-				},
-				Status: pgtype.Present,
-			},
-		},
-		{
-			sql: `select null::record`,
-			expected: pgtype.Record{
-				Status: pgtype.Null,
-			},
-		},
-	}
-
-	for i, tt := range tests {
+	for i, tt := range recordTests {
 		psName := fmt.Sprintf("test%d", i)
 		_, err := conn.Prepare(context.Background(), psName, tt.sql)
 		if err != nil {
 			t.Fatal(err)
 		}
 
-		var result pgtype.Record
-		if err := conn.QueryRow(context.Background(), psName, pgx.QueryResultFormats{pgx.BinaryFormatCode}).Scan(&result); err != nil {
-			t.Errorf("%d: %v", i, err)
-			continue
-		}
+		t.Run(tt.sql, func(t *testing.T) {
+			var result pgtype.Record
+			if err := conn.QueryRow(context.Background(), psName, pgx.QueryResultFormats{pgx.BinaryFormatCode}).Scan(&result); err != nil {
+				t.Errorf("%v", err)
+				return
+			}
+
+			if !reflect.DeepEqual(tt.expected, result) {
+				t.Errorf("expected %#v, got %#v", tt.expected, result)
+			}
+		})
 
-		if !reflect.DeepEqual(tt.expected, result) {
-			t.Errorf("%d: expected %#v, got %#v", i, tt.expected, result)
-		}
 	}
 }