synchronized void save() {
Long lastKey = this.lastSyncKey;
Set<Entry<Long, RedoLogValue>> entrySet =
lastKey == null ? skipListMap.entrySet() : skipListMap.tailMap(lastKey, false).entrySet();
if (!entrySet.isEmpty()) {
WriteBuffer buff = WriteBufferPool.poll();
try {
for (Entry<Long, RedoLogValue> e : entrySet) {
lastKey = e.getKey();
keyType.write(buff, lastKey);
valueType.write(buff, e.getValue());
}
int chunkLength = buff.position();
if (chunkLength > 0) {
buff.limit(chunkLength);
buff.position(0);
fileStorage.writeFully(pos, buff.getBuffer());
pos += chunkLength;
fileStorage.sync();
}
this.lastSyncKey = lastKey;
} finally {
WriteBufferPool.offer(buff);
}
}
}
/**
* Get a buffer for writing. This caller must synchronize on the storage before calling the method
* and until after using the buffer.
*
* @return the buffer
*/
private WriteBuffer getWriteBuffer() {
WriteBuffer buff;
if (writeBuffer != null) {
buff = writeBuffer;
buff.clear();
} else {
buff = new WriteBuffer();
}
return buff;
}
private long save() {
int currentUnsavedMemory = unsavedMemory;
long version = ++currentVersion;
long time = getTimeSinceCreation();
lastCommitTime = time;
WriteBuffer buff = getWriteBuffer();
BTreeChunk c = new BTreeChunk(++lastChunkId);
chunks.put(c.id, c);
c.time = time;
c.version = version;
c.pagePositions = new ArrayList<Long>();
BTreePage p = map.root;
if (p.getTotalCount() > 0) {
p.writeUnsavedRecursive(c, buff);
c.rootPagePos = p.getPos();
p.writeEnd();
}
c.pagePositionsOffset = buff.position();
for (long pos : c.pagePositions) buff.putLong(pos);
int chunkBodyLength = buff.position();
chunkBodyLength = MathUtils.roundUpInt(chunkBodyLength, BLOCK_SIZE);
buff.limit(chunkBodyLength);
buff.position(0);
c.blockCount =
chunkBodyLength / BLOCK_SIZE + CHUNK_HEADER_BLOCKS; // include chunk header(2 blocks).
c.fileStorage = getFileStorage(c.id);
// chunk header
writeChunkHeader(c);
// chunk body
write(c.fileStorage, CHUNK_HEADER_SIZE, buff.getBuffer());
c.fileStorage.sync();
for (BTreeChunk chunk : chunks.values()) {
if (chunk.changed) {
writeChunkHeader(chunk);
chunk.fileStorage.sync();
chunk.changed = false;
}
}
releaseWriteBuffer(buff);
// some pages might have been changed in the meantime (in the newest version)
unsavedMemory = Math.max(0, unsavedMemory - currentUnsavedMemory);
lastStoredVersion = version - 1;
return version;
}
/**
* Release a buffer for writing. This caller must synchronize on the storage before calling the
* method and until after using the buffer.
*
* @param buff the buffer than can be re-used
*/
private void releaseWriteBuffer(WriteBuffer buff) {
if (buff.capacity() <= 4 * 1024 * 1024) {
writeBuffer = buff;
}
}