THUMarkLau commented on code in PR #12476:
URL: https://github.com/apache/iotdb/pull/12476#discussion_r1632198623
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iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/wal/utils/WALEntryPosition.java:
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@@ -100,11 +101,11 @@ ByteBuffer read() throws IOException {
if (!canRead()) {
throw new IOException("Target file hasn't been specified.");
}
- try (FileChannel channel = openReadFileChannel()) {
+ try (WALInputStream is = openReadFileStream()) {
+ is.skipToGivenPosition(position);
ByteBuffer buffer = ByteBuffer.allocate(size);
- channel.position(position);
- channel.read(buffer);
- buffer.clear();
+ is.read(buffer);
+ buffer.flip();
return buffer;
}
Review Comment:
My response is the same as in the previous comments: this is how the
original design was implemented. I just made slight modifications to make it
suitable for compressed cases. Theoretically, the performance is similar to the
original since the original design involved opening a Channel, and a
WALInputStream essentially operates as a Channel. Sharing the Stream is a
reasonable suggestion, but it is unrelated to the current task (Write Ahead Log
compression) and may introduce other bugs and performance issues, so I will not
be modifying this part of the code.
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