Fix: support image type for bulkcopy

Author: dlapko

bulkcopy.go

@@ -599,7 +599,7 @@ func (b *Bulk) makeParam(val DataValue, col columnStruct) (res param, err error)
 			buf[i] = ub[j]
 		}
 		res.buffer = buf
-	case typeBigVarBin, typeBigBinary:
+	case typeBigVarBin, typeBigBinary, typeImage:
 		switch val := val.(type) {
 		case []byte:
 			res.ti.Size = len(val)

bulkcopy_test.go

@@ -200,6 +200,8 @@ func testBulkcopy(t *testing.T, guidConversion bool) {
 		{"test_int16nvarchar", int16(1234), "1234"},
 		{"test_int8nvarchar", int8(12), "12"},
 		{"test_intnvarchar", 1234, "1234"},
+		{"test_image", []byte("1"), nil},
+		{"test_imagen", nil, nil},
 	}
 
 	columns := make([]string, len(testValues))
@@ -449,6 +451,8 @@ func setupTable(ctx context.Context, t *testing.T, conn *sql.Conn, tableName str
 	[test_nullint32] [int] NULL,
 	[test_nullint16] [smallint] NULL,
 	[test_nulltime] [datetime] NULL,
+	[test_image] [image] NOT NULL,
+	[test_imagen] [image] NULL,
  CONSTRAINT [PK_` + tableName + `_id] PRIMARY KEY CLUSTERED
 (
 	[id] ASC

types.go

@@ -254,8 +254,16 @@ func writeVarLen(w io.Writer, ti *typeInfo, out bool, encoding msdsn.EncodeParam
 		if err = binary.Write(w, binary.LittleEndian, uint32(ti.Size)); err != nil {
 			return
 		}
-		if err = writeCollation(w, ti.Collation); err != nil {
-			return
+
+		// COLLATION occurs only if the type is BIGCHARTYPE, BIGVARCHARTYPE, TEXTTYPE, NTEXTTYPE,
+		// NCHARTYPE, or NVARCHARTYPE.
+		//
+		// https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-tds/cbe9c510-eae6-4b1f-9893-a098944d430a
+		switch ti.TypeId {
+		case typeText, typeNText:
+			if err = writeCollation(w, ti.Collation); err != nil {
+				return
+			}
 		}
 		ti.Writer = writeLongLenType
 	default:
@@ -1333,6 +1341,8 @@ func makeDecl(ti typeInfo) string {
 		return "ntext"
 	case typeUdt:
 		return ti.UdtInfo.TypeName
+	case typeImage:
+		return "image"
 	case typeGuid:
 		return "uniqueidentifier"
 	case typeTvp: