address comments

util/chunk/disk.go

@@ -33,16 +33,17 @@ import (
 type ListInDisk struct {
 	fieldTypes         []*types.FieldType
 	numRowForEachChunk []int
-	numRowPrefixSum    []int
+	numRowPrefixSum    []int // indicates the offsets of each chunk's offsets in OffsetFile.
+	numRowsInDisk      int
+	diskTracker        *disk.Tracker // track disk usage.
 
-	numRowsInDisk int
-	diskTracker   *disk.Tracker // track disk usage.
-
-	dataFile   tempFileWithIOWrapper
-	offsetFile tempFileWithIOWrapper
+	dataFile   diskFileReaderWriter
+	offsetFile diskFileReaderWriter
 }
 
-type tempFileWithIOWrapper struct {
+// diskFileReaderWriter represents a Reader and a Writer for the temporary disk file,
+// without considering the detail of checksum and encryption.
+type diskFileReaderWriter struct {
 	disk *os.File
 	w    io.WriteCloser
 	// offWrite is the current offset for writing.
@@ -55,7 +56,7 @@ type tempFileWithIOWrapper struct {
 	ctrCipher *encrypt.CtrCipher
 }
 
-func (l *tempFileWithIOWrapper) initWithFileName(fileName string) (err error) {
+func (l *diskFileReaderWriter) initWithFileName(fileName string) (err error) {
 	l.disk, err = os.CreateTemp(config.GetGlobalConfig().TempStoragePath, fileName)
 	if err != nil {
 		return errors2.Trace(err)
@@ -75,7 +76,7 @@ func (l *tempFileWithIOWrapper) initWithFileName(fileName string) (err error) {
 	return
 }
 
-func (l *tempFileWithIOWrapper) getReader() io.ReaderAt {
+func (l *diskFileReaderWriter) getReader() io.ReaderAt {
 	var underlying io.ReaderAt = l.disk
 	if l.ctrCipher != nil {
 		underlying = NewReaderWithCache(encrypt.NewReader(l.disk, l.ctrCipher), l.cipherWriter.GetCache(), l.cipherWriter.GetCacheDataOffset())
@@ -86,13 +87,13 @@ func (l *tempFileWithIOWrapper) getReader() io.ReaderAt {
 	return underlying
 }
 
-func (l *tempFileWithIOWrapper) getSelectionReader(off int64) *io.SectionReader {
+func (l *diskFileReaderWriter) getSectionReader(off int64) *io.SectionReader {
 	checksumReader := l.getReader()
 	r := io.NewSectionReader(checksumReader, off, l.offWrite-off)
 	return r
 }
 
-func (l *tempFileWithIOWrapper) getWriter() io.Writer {
+func (l *diskFileReaderWriter) getWriter() io.Writer {
 	return l.w
 }
 
@@ -188,7 +189,7 @@ func (l *ListInDisk) GetRow(ptr RowPtr) (row Row, err error) {
 	if err != nil {
 		return
 	}
-	r := l.dataFile.getSelectionReader(off)
+	r := l.dataFile.getSectionReader(off)
 	format := rowInDisk{numCol: len(l.fieldTypes)}
 	_, err = format.ReadFrom(r)
 	if err != nil {
@@ -201,13 +202,13 @@ func (l *ListInDisk) GetRow(ptr RowPtr) (row Row, err error) {
 func (l *ListInDisk) getOffset(chkIdx uint32, rowIdx uint32) (int64, error) {
 	offsetInOffsetFile := l.numRowPrefixSum[chkIdx] + int(rowIdx)
 	b := make([]byte, 8)
-	reader := l.offsetFile.getSelectionReader(int64(offsetInOffsetFile) * 8)
+	reader := l.offsetFile.getSectionReader(int64(offsetInOffsetFile) * 8)
 	n, err := io.ReadFull(reader, b)
 	if err != nil {
 		return 0, err
 	}
 	if n != 8 {
-		return 0, errors2.New("Can not get offset from disk")
+		return 0, errors2.New("The file spilled is broken, can not get data offset from the disk")
 	}
 	return bytesToI64Slice(b)[0], nil
 }
@@ -260,6 +261,12 @@ type chunkInDisk struct {
 
 type offsetsOfRows []int64
 
+// WriteTo serializes the offsetsOfRow, and writes to w.
+func (off offsetsOfRows) WriteTo(w io.Writer) (written int64, err error) {
+	n, err := w.Write(i64SliceToBytes(off))
+	return int64(n), err
+}
+
 // WriteTo serializes the chunk into the format of chunkInDisk, and
 // writes to w.
 func (chk *chunkInDisk) WriteTo(w io.Writer) (written int64, err error) {
@@ -283,12 +290,6 @@ func (chk *chunkInDisk) WriteTo(w io.Writer) (written int64, err error) {
 // getOffsetsOfRows gets the offset of each row.
 func (chk *chunkInDisk) getOffsetsOfRows() offsetsOfRows { return chk.offsetsOfRows }
 
-// WriteTo serializes the offsetsOfRow, and writes to w.
-func (off offsetsOfRows) WriteTo(w io.Writer) (written int64, err error) {
-	n, err := w.Write(i64SliceToBytes(off))
-	return int64(n), err
-}
-
 // rowInDisk represents a Row in format of diskFormatRow.
 type rowInDisk struct {
 	numCol int

util/chunk/disk_test.go

@@ -143,7 +143,7 @@ type listInDiskWriteDisk struct {
 	ListInDisk
 }
 
-func (l *tempFileWithIOWrapper) flushForTest() (err error) {
+func (l *diskFileReaderWriter) flushForTest() (err error) {
 	err = l.disk.Close()
 	if err != nil {
 		return