/// <summary>
/// There are two files: sourceFile and targetFile. Blocks are merged, mergeFactor at the time, from source to target. When all blocks from source have
/// been merged into a larger block one merge iteration is done and source and target are flipped. As long as source contain more than a single block more
/// merge iterations are needed and we start over again.
/// When source only contain a single block we are finished and the extra file is deleted and <seealso cref="blockFile"/> contains the result with a single sorted
/// block.
///
/// See <seealso cref="performSingleMerge(int, BlockReader, StoreChannel, Cancellation, ByteBuffer[], ByteBuffer)"/> for further details.
/// </summary>
/// <param name="mergeFactor"> See <seealso cref="performSingleMerge(int, BlockReader, StoreChannel, Cancellation, ByteBuffer[], ByteBuffer)"/>. </param>
/// <param name="cancellation"> Injected so that this merge can be cancelled, if an external request to do that comes in.
/// A cancelled merge will leave the same end state file/channel-wise, just not quite completed, which is fine because the merge
/// was cancelled meaning that the result will not be used for anything other than deletion. </param>
/// <exception cref="IOException"> If something goes wrong when reading from file. </exception>
//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in C#:
//ORIGINAL LINE: public void merge(int mergeFactor, Cancellation cancellation) throws java.io.IOException
public virtual void Merge(int mergeFactor, Cancellation cancellation)
{
_monitor.mergeStarted(_entryCount, CalculateNumberOfEntriesWrittenDuringMerges(_entryCount, _numberOfBlocksInCurrentFile, mergeFactor));
File sourceFile = _blockFile;
File tempFile = new File(_blockFile.Parent, _blockFile.Name + ".b");
try
{
using (Allocator mergeBufferAllocator = _bufferFactory.newLocalAllocator())
{
File targetFile = tempFile;
// Allocate all buffers that will be used and reused for all merge iterations
ByteBuffer writeBuffer = mergeBufferAllocator.Allocate(_bufferFactory.bufferSize());
ByteBuffer[] readBuffers = new ByteBuffer[mergeFactor];
for (int i = 0; i < readBuffers.Length; i++)
{
readBuffers[i] = mergeBufferAllocator.Allocate(_bufferFactory.bufferSize());
}
while (_numberOfBlocksInCurrentFile > 1)
{
// Perform one complete merge iteration, merging all blocks from source into target.
// After this step, target will contain fewer blocks than source, but may need another merge iteration.
using (BlockReader <KEY, VALUE> reader = reader(sourceFile), StoreChannel targetChannel = _fs.open(targetFile, OpenMode.READ_WRITE))
{
long blocksMergedSoFar = 0;
long blocksInMergedFile = 0;
while (!cancellation.Cancelled() && blocksMergedSoFar < _numberOfBlocksInCurrentFile)
{
blocksMergedSoFar += PerformSingleMerge(mergeFactor, reader, targetChannel, cancellation, readBuffers, writeBuffer);
blocksInMergedFile++;
}
_numberOfBlocksInCurrentFile = blocksInMergedFile;
_monitor.mergeIterationFinished(blocksMergedSoFar, blocksInMergedFile);
}
// Flip and restore the channels
File tmpSourceFile = sourceFile;
sourceFile = targetFile;
targetFile = tmpSourceFile;
}
}
}
finally
{
if (sourceFile == _blockFile)
{
_fs.deleteFile(tempFile);
}
else
{
_fs.deleteFile(_blockFile);
_fs.renameFile(tempFile, _blockFile);
}
}
}
//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in C#:
//ORIGINAL LINE: private static <KEY, VALUE> long writeEntries(org.neo4j.io.fs.StoreChannel targetChannel, ByteBuffer byteBuffer, org.neo4j.index.internal.gbptree.Layout<KEY,VALUE> layout, BlockEntryCursor<KEY,VALUE> blockEntryCursor, Cancellation cancellation, System.Action<int> entryCountReporter) throws java.io.IOException
private static long WriteEntries <KEY, VALUE>(StoreChannel targetChannel, ByteBuffer byteBuffer, Layout <KEY, VALUE> layout, BlockEntryCursor <KEY, VALUE> blockEntryCursor, Cancellation cancellation, System.Action <int> entryCountReporter)
{
// Loop over block entries
long actualDataSize = BlockHeaderSize;
ByteArrayPageCursor pageCursor = new ByteArrayPageCursor(byteBuffer);
int entryCountToReport = 0;
while (blockEntryCursor.Next())
{
KEY key = blockEntryCursor.Key();
VALUE value = blockEntryCursor.Value();
int entrySize = BlockEntry.EntrySize(layout, key, value);
actualDataSize += entrySize;
entryCountToReport++;
if (byteBuffer.remaining() < entrySize)
{
// First check if this merge have been cancelled, if so just break here, it's fine.
if (cancellation.Cancelled())
{
break;
}
// flush and reset + DON'T PAD!!!
byteBuffer.flip();
targetChannel.WriteAll(byteBuffer);
byteBuffer.clear();
entryCountReporter(entryCountToReport);
entryCountToReport = 0;
}
BlockEntry.Write(pageCursor, layout, key, value);
}
if (entryCountToReport > 0)
{
entryCountReporter(entryCountToReport);
}
return(actualDataSize);
}
