public SeekingIteratorAdapter iterator(ReadOptions options) {
checkBackgroundException();
mutex.lock();
try {
DbIterator rawIterator = internalIterator();
// filter any entries not visible in our snapshot
SnapshotImpl snapshot = getSnapshot(options);
SnapshotSeekingIterator snapshotIterator =
new SnapshotSeekingIterator(
rawIterator, snapshot, internalKeyComparator.getUserComparator());
return new SeekingIteratorAdapter(snapshotIterator);
} finally {
mutex.unlock();
}
}
private void doCompactionWork(CompactionState compactionState) throws IOException {
Preconditions.checkState(mutex.isHeldByCurrentThread());
Preconditions.checkArgument(
versions.numberOfBytesInLevel(compactionState.getCompaction().getLevel()) > 0);
Preconditions.checkArgument(compactionState.builder == null);
Preconditions.checkArgument(compactionState.outfile == null);
// todo track snapshots
compactionState.smallestSnapshot = versions.getLastSequence();
// Release mutex while we're actually doing the compaction work
mutex.unlock();
try {
MergingIterator iterator = versions.makeInputIterator(compactionState.compaction);
Slice currentUserKey = null;
boolean hasCurrentUserKey = false;
long lastSequenceForKey = MAX_SEQUENCE_NUMBER;
while (iterator.hasNext() && !shuttingDown.get()) {
// always give priority to compacting the current mem table
mutex.lock();
try {
compactMemTableInternal();
} finally {
mutex.unlock();
}
InternalKey key = iterator.peek().getKey();
if (compactionState.compaction.shouldStopBefore(key) && compactionState.builder != null) {
finishCompactionOutputFile(compactionState);
}
// Handle key/value, add to state, etc.
boolean drop = false;
// todo if key doesn't parse (it is corrupted),
if (false /*!ParseInternalKey(key, &ikey)*/) {
// do not hide error keys
currentUserKey = null;
hasCurrentUserKey = false;
lastSequenceForKey = MAX_SEQUENCE_NUMBER;
} else {
if (!hasCurrentUserKey
|| internalKeyComparator.getUserComparator().compare(key.getUserKey(), currentUserKey)
!= 0) {
// First occurrence of this user key
currentUserKey = key.getUserKey();
hasCurrentUserKey = true;
lastSequenceForKey = MAX_SEQUENCE_NUMBER;
}
if (lastSequenceForKey <= compactionState.smallestSnapshot) {
// Hidden by an newer entry for same user key
drop = true; // (A)
} else if (key.getValueType() == ValueType.DELETION
&& key.getSequenceNumber() <= compactionState.smallestSnapshot
&& compactionState.compaction.isBaseLevelForKey(key.getUserKey())) {
// For this user key:
// (1) there is no data in higher levels
// (2) data in lower levels will have larger sequence numbers
// (3) data in layers that are being compacted here and have
// smaller sequence numbers will be dropped in the next
// few iterations of this loop (by rule (A) above).
// Therefore this deletion marker is obsolete and can be dropped.
drop = true;
}
lastSequenceForKey = key.getSequenceNumber();
}
if (!drop) {
// Open output file if necessary
if (compactionState.builder == null) {
openCompactionOutputFile(compactionState);
}
if (compactionState.builder.getEntryCount() == 0) {
compactionState.currentSmallest = key;
}
compactionState.currentLargest = key;
compactionState.builder.add(key.encode(), iterator.peek().getValue());
// Close output file if it is big enough
if (compactionState.builder.getFileSize()
>= compactionState.compaction.getMaxOutputFileSize()) {
finishCompactionOutputFile(compactionState);
}
}
iterator.next();
}
if (shuttingDown.get()) {
throw new DatabaseShutdownException("DB shutdown during compaction");
}
if (compactionState.builder != null) {
finishCompactionOutputFile(compactionState);
}
} finally {
mutex.lock();
}
// todo port CompactionStats code
installCompactionResults(compactionState);
}