netudima commented on code in PR #3606:
URL: https://github.com/apache/cassandra/pull/3606#discussion_r1938584331
##########
src/java/org/apache/cassandra/io/util/CompressedChunkReader.java:
##########
@@ -83,20 +90,167 @@ public BufferType preferredBufferType()
}
@Override
- public Rebufferer instantiateRebufferer()
+ public Rebufferer instantiateRebufferer(boolean isScan)
{
- return new BufferManagingRebufferer.Aligned(this);
+ return new BufferManagingRebufferer.Aligned(isScan ? forScan() : this);
}
- public static class Standard extends CompressedChunkReader
+ protected interface CompressedReader extends Closeable
+ {
+ default void allocateResources()
+ {
+ }
+
+ default void deallocateResources()
+ {
+ }
+
+ default boolean allocated()
+ {
+ return false;
+ }
+
+ default void close()
+ {
+
+ }
+
+
+ ByteBuffer read(CompressionMetadata.Chunk chunk, boolean
shouldCheckCrc) throws CorruptBlockException;
+ }
+
+ private static class RandomAccessCompressedReader implements
CompressedReader
+ {
+ private final ChannelProxy channel;
+ private final ThreadLocalByteBufferHolder bufferHolder;
+
+ private RandomAccessCompressedReader(ChannelProxy channel,
CompressionMetadata metadata)
+ {
+ this.channel = channel;
+ this.bufferHolder = new
ThreadLocalByteBufferHolder(metadata.compressor().preferredBufferType());
+ }
+
+ @Override
+ public ByteBuffer read(CompressionMetadata.Chunk chunk, boolean
shouldCheckCrc) throws CorruptBlockException
+ {
+ int length = shouldCheckCrc ? chunk.length + Integer.BYTES //
compressed length + checksum length
+ : chunk.length;
+ ByteBuffer compressed = bufferHolder.getBuffer(length);
+ if (channel.read(compressed, chunk.offset) != length)
+ throw new CorruptBlockException(channel.filePath(), chunk);
+ compressed.flip();
+ compressed.limit(chunk.length);
+
+ if (shouldCheckCrc)
+ {
+ int checksum = (int) ChecksumType.CRC32.of(compressed);
+ compressed.limit(length);
+ if (compressed.getInt() != checksum)
+ throw new CorruptBlockException(channel.filePath(), chunk);
+ compressed.position(0).limit(chunk.length);
+ }
+ return compressed;
+ }
+ }
+
+ private static class ScanCompressedReader implements CompressedReader
{
- // we read the raw compressed bytes into this buffer, then
uncompressed them into the provided one.
+ private final ChannelProxy channel;
private final ThreadLocalByteBufferHolder bufferHolder;
+ private final ThreadLocalReadAheadBuffer readAheadBuffer;
+
+ private ScanCompressedReader(ChannelProxy channel, CompressionMetadata
metadata, int readAheadBufferSize)
+ {
+ this.channel = channel;
+ this.bufferHolder = new
ThreadLocalByteBufferHolder(metadata.compressor().preferredBufferType());
+ this.readAheadBuffer = new ThreadLocalReadAheadBuffer(channel,
readAheadBufferSize, metadata.compressor().preferredBufferType());
+ }
+
+ @Override
+ public ByteBuffer read(CompressionMetadata.Chunk chunk, boolean
shouldCheckCrc) throws CorruptBlockException
+ {
+ int length = shouldCheckCrc ? chunk.length + Integer.BYTES //
compressed length + checksum length
+ : chunk.length;
+ ByteBuffer compressed = bufferHolder.getBuffer(length);
+
+ int copied = 0;
+ while (copied < length) {
Review Comment:
the last idea, please fill free to ignore it :-)
we can move the whole loop into the readAheadBuffer logic and do a single
thread local lookup for a block in such case (currently we do 3 or 4 lookups
per loop iteration). It also will remove a duplicated code from a test.
like:
```
public void read(ByteBuffer target, long offset, int length)
{
int copied = 0;
Block block = getBlock();
while (copied < length)
{
fill(block, offset + copied);
int leftToRead = length - copied;
if (block.buffer.remaining() >= leftToRead)
copied += read(block, target, leftToRead);
else
copied += read(block, target, block.buffer.remaining());
}
}
```
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