Revert "[dbnode] Validate individual index entries on decode instead …

…of entire file on open (#2468)"

This reverts commit bba274f.

src/dbnode/persist/fs/msgpack/decoder.go

@@ -46,18 +46,14 @@ var (
 
 	errorUnableToDetermineNumFieldsToSkip          = errors.New("unable to determine num fields to skip")
 	errorCalledDecodeBytesWithoutByteStreamDecoder = errors.New("called decodeBytes with out byte stream decoder")
-	errorIndexEntryChecksumMismatch                = errors.New("decode index entry encountered checksum mismatch")
 )
 
 // Decoder decodes persisted msgpack-encoded data
 type Decoder struct {
 	reader DecoderStream
 	// Will only be set if the Decoder is Reset() with a DecoderStream
 	// that also implements ByteStream.
-	byteReader ByteStream
-	// Wraps original reader with reader that can calculate digest. Digest calculation must be enabled,
-	// otherwise it defaults to off.
-	readerWithDigest  *decoderStreamWithDigest
+	byteReader        ByteStream
 	dec               *msgpack.Decoder
 	err               error
 	allocDecodedBytes bool
@@ -80,7 +76,6 @@ func newDecoder(legacy legacyEncodingOptions, opts DecodingOptions) *Decoder {
 		reader:            reader,
 		dec:               msgpack.NewDecoder(reader),
 		legacy:            legacy,
-		readerWithDigest:  newDecoderStreamWithDigest(nil),
 	}
 }
 
@@ -96,8 +91,7 @@ func (dec *Decoder) Reset(stream DecoderStream) {
 		dec.byteReader = nil
 	}
 
-	dec.readerWithDigest.reset(dec.reader)
-	dec.dec.Reset(dec.readerWithDigest)
+	dec.dec.Reset(dec.reader)
 	dec.err = nil
 }
 
@@ -121,10 +115,8 @@ func (dec *Decoder) DecodeIndexEntry(bytesPool pool.BytesPool) (schema.IndexEntr
 	if dec.err != nil {
 		return emptyIndexEntry, dec.err
 	}
-	dec.readerWithDigest.setDigestReaderEnabled(true)
 	_, numFieldsToSkip := dec.decodeRootObject(indexEntryVersion, indexEntryType)
 	indexEntry := dec.decodeIndexEntry(bytesPool)
-	dec.readerWithDigest.setDigestReaderEnabled(false)
 	dec.skip(numFieldsToSkip)
 	if dec.err != nil {
 		return emptyIndexEntry, dec.err
@@ -414,22 +406,13 @@ func (dec *Decoder) decodeIndexEntry(bytesPool pool.BytesPool) schema.IndexEntry
 		return indexEntry
 	}
 
-	// NB(nate): Any new fields should be parsed here.
-
 	// Intentionally skip any extra fields here as we've stipulated that from V3 onward, IndexEntryChecksum will be the
 	// final field on index entries
 	dec.skip(numFieldsToSkip)
 
-	// Retrieve actual checksum value here. Attempting to retrieve after decoding the upcoming expected checksum field
-	// would include value in actual checksum calculation which would cause a mismatch
-	actualChecksum := dec.readerWithDigest.digest().Sum32()
-
 	// Decode checksum field originally added in V3
-	expectedChecksum := uint32(dec.decodeVarint())
-
-	if expectedChecksum != actualChecksum {
-		dec.err = errorIndexEntryChecksumMismatch
-	}
+	// TODO(nate): actually use the checksum value for index entry validation - #2629
+	_ = dec.decodeVarint()
 
 	return indexEntry
 }
@@ -680,11 +663,6 @@ func (dec *Decoder) decodeBytes() ([]byte, int, int) {
 		return nil, -1, -1
 	}
 	value = backingBytes[currPos:targetPos]
-	if err := dec.readerWithDigest.capture(value); err != nil {
-		dec.err = err
-		return nil, -1, -1
-	}
-
 	return value, currPos, bytesLen
 }
 
@@ -702,7 +680,7 @@ func (dec *Decoder) decodeBytesWithPool(bytesPool pool.BytesPool) []byte {
 	}
 
 	bytes := bytesPool.Get(bytesLen)[:bytesLen]
-	n, err := io.ReadFull(dec.readerWithDigest, bytes)
+	n, err := io.ReadFull(dec.reader, bytes)
 	if err != nil {
 		dec.err = err
 		bytesPool.Put(bytes)

src/dbnode/persist/fs/msgpack/decoder_test.go

@@ -262,19 +262,3 @@ func TestDecodeBytesAllocNew(t *testing.T) {
 	}
 	require.Equal(t, []byte("testIndexEntry"), res.ID)
 }
-
-func TestDecodeIndexEntryInvalidChecksum(t *testing.T) {
-	var (
-		enc = NewEncoder()
-		dec = NewDecoder(nil)
-	)
-	require.NoError(t, enc.EncodeIndexEntry(testIndexEntry))
-
-	// Update to invalid checksum
-	enc.buf.Truncate(len(enc.Bytes()) - 5) // 5 bytes = 1 byte for integer code + 4 bytes for checksum
-	require.NoError(t, enc.enc.EncodeInt64(1234))
-
-	dec.Reset(NewByteDecoderStream(enc.Bytes()))
-	_, err := dec.DecodeIndexEntry(nil)
-	require.Error(t, err)
-}