JackieTien97 commented on code in PR #12447:
URL: https://github.com/apache/iotdb/pull/12447#discussion_r1584008968
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iotdb-core/datanode/src/main/java/org/apache/iotdb/db/schemaengine/schemaregion/tag/TagLogFile.java:
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@@ -95,22 +102,85 @@ public synchronized void copyTo(File targetFile) throws
IOException {
* @return tags map, attributes map
* @throws IOException error occurred when reading disk
*/
- public Pair<Map<String, String>, Map<String, String>> read(int size, long
position)
- throws IOException {
+ public Pair<Map<String, String>, Map<String, String>> read(long position)
throws IOException {
if (position < 0) {
return new Pair<>(Collections.emptyMap(), Collections.emptyMap());
}
- ByteBuffer byteBuffer = ByteBuffer.allocate(size);
+ ByteBuffer byteBuffer = parseByteBuffer(fileChannel, position);
+ return new Pair<>(ReadWriteIOUtils.readMap(byteBuffer),
ReadWriteIOUtils.readMap(byteBuffer));
+ }
+
+ public Map<String, String> readTag(long position) throws IOException {
+ ByteBuffer byteBuffer = parseByteBuffer(fileChannel, position);
+ return ReadWriteIOUtils.readMap(byteBuffer);
+ }
+
+ public static ByteBuffer parseByteBuffer(FileChannel fileChannel, long
position)
+ throws IOException {
+ // Read the first block
+ ByteBuffer byteBuffer = ByteBuffer.allocate(MAX_LENGTH);
fileChannel.read(byteBuffer, position);
byteBuffer.flip();
- return new Pair<>(ReadWriteIOUtils.readMap(byteBuffer),
ReadWriteIOUtils.readMap(byteBuffer));
+ if (byteBuffer.limit() > 0) { // This indicates that there is data at this
position
+ int firstInt = ReadWriteIOUtils.readInt(byteBuffer); // first int
+ byteBuffer.position(0);
+ if (firstInt < -1) { // This position is blockNum, the original data
occupies multiple blocks
+ int blockNum = -firstInt;
+ ByteBuffer byteBuffers = ByteBuffer.allocate(blockNum * MAX_LENGTH);
+ byteBuffers.put(byteBuffer);
+ byteBuffers.position(4); // Skip blockNum
+ List<Long> blockOffset = new ArrayList<>();
+ blockOffset.add(position);
+ for (int i = 1; i < blockNum; i++) {
+ blockOffset.add(ReadWriteIOUtils.readLong(byteBuffers));
+ // read one offset, then use filechannel's read to read it
+ byteBuffers.position(MAX_LENGTH * i);
+ byteBuffers.limit(MAX_LENGTH * (i + 1));
+ fileChannel.read(byteBuffers, blockOffset.get(i));
+ byteBuffers.position(4 + i * Long.BYTES);
+ }
+ byteBuffers.limit(byteBuffers.capacity());
+ return byteBuffers;
+ }
+ }
+ return byteBuffer;
}
- public Map<String, String> readTag(int size, long position) throws
IOException {
- ByteBuffer byteBuffer = ByteBuffer.allocate(size);
+ private List<Long> ParseOffsetList(long position) throws IOException {
+ List<Long> blockOffset = new ArrayList<>();
+ blockOffset.add(position);
+ // Read the first block
+ ByteBuffer byteBuffer = ByteBuffer.allocate(MAX_LENGTH);
fileChannel.read(byteBuffer, position);
byteBuffer.flip();
- return ReadWriteIOUtils.readMap(byteBuffer);
+ if (byteBuffer.limit() > 0) { // This indicates that there is data at this
position
+ int firstInt = ReadWriteIOUtils.readInt(byteBuffer); // first int
+ byteBuffer.position(0);
+ if (firstInt < -1) { // This position is blockNum, the original data
occupies multiple blocks
+ int blockNum = -firstInt;
+ int blockOffsetStoreLen =
+ (((blockNum - 1) * Long.BYTES + 4) / MAX_LENGTH + 1)
+ * MAX_LENGTH; // blockOffset storage length
+ ByteBuffer blockBuffer = ByteBuffer.allocate(blockOffsetStoreLen);
+ blockBuffer.put(byteBuffer);
+ blockBuffer.position(4); // Skip blockNum
+
+ for (int i = 1; i < blockNum; i++) {
+ blockOffset.add(ReadWriteIOUtils.readLong(blockBuffer));
+ // Every time you read an offset, use filechannel's read to read it
+ if (MAX_LENGTH * (i + 1)
+ <= blockOffsetStoreLen) { // Compared with directly reading
bytebuffer, some reading
+ // operations are reduced, only the content of offset is
+ // read
+ blockBuffer.position(MAX_LENGTH * i);
+ blockBuffer.limit(MAX_LENGTH * (i + 1));
+ fileChannel.read(blockBuffer, blockOffset.get(i));
+ blockBuffer.position(4 + i * Long.BYTES);
+ }
+ }
Review Comment:
You've already read all the first block content into memory in previous
`fileChannel.read(byteBuffer, position);`
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