/**
* @param ref The ref.
* @return The offset to list record pointer; list record is created if it doesn't exist.
*/
private long createOrGetListRecord(long ref) {
if (Ref.hasList(ref)) {
// LOG.info("Found list record at " + writeBuffers.getReadPoint());
return writeBuffers.getReadPoint(); // Assumes we are here after key compare.
}
long firstTailOffset = Ref.getOffset(ref);
// LOG.info("First tail offset to create list record is " + firstTailOffset);
// Determine the length of storage for value and key lengths of the first record.
writeBuffers.setReadPoint(firstTailOffset);
writeBuffers.skipVLong();
writeBuffers.skipVLong();
int lengthsLength = (int) (writeBuffers.getReadPoint() - firstTailOffset);
// Create the list record, copy first record value/key lengths there.
writeBuffers.writeBytes(firstTailOffset, lengthsLength);
long lrPtrOffset = writeBuffers.getWritePoint();
// LOG.info("Creating list record: copying " + lengthsLength + ", lrPtrOffset " + lrPtrOffset);
// Reserve 5 bytes for writeValueRecord to fill. There might be junk there so null them.
writeBuffers.write(FIVE_ZEROES);
// Link the list record to the first element.
writeBuffers.writeFiveByteULong(firstTailOffset, lrPtrOffset - lengthsLength - firstTailOffset);
return lrPtrOffset;
}
/** Writes the debug dump of the table into logs. Not thread-safe. */
public void debugDumpTable() {
StringBuilder dump = new StringBuilder(keysAssigned + " keys\n");
TreeMap<Long, Integer> byteIntervals = new TreeMap<Long, Integer>();
int examined = 0;
for (int slot = 0; slot < refs.length; ++slot) {
long ref = refs[slot];
if (ref == 0) {
continue;
}
++examined;
long recOffset = getFirstRecordLengthsOffset(ref, null);
long tailOffset = Ref.getOffset(ref);
writeBuffers.setReadPoint(recOffset);
int valueLength = (int) writeBuffers.readVLong(), keyLength = (int) writeBuffers.readVLong();
long ptrOffset = writeBuffers.getReadPoint();
if (Ref.hasList(ref)) {
byteIntervals.put(recOffset, (int) (ptrOffset + 5 - recOffset));
}
long keyOffset = tailOffset - valueLength - keyLength;
byte[] key = new byte[keyLength];
WriteBuffers.ByteSegmentRef fakeRef = new WriteBuffers.ByteSegmentRef(keyOffset, keyLength);
byteIntervals.put(keyOffset - 4, keyLength + 4);
writeBuffers.populateValue(fakeRef);
System.arraycopy(fakeRef.getBytes(), (int) fakeRef.getOffset(), key, 0, keyLength);
dump.append(Utils.toStringBinary(key, 0, key.length))
.append(" ref [")
.append(dumpRef(ref))
.append("]: ");
Result hashMapResult = new Result();
getValueResult(key, 0, key.length, hashMapResult);
List<WriteBuffers.ByteSegmentRef> results = new ArrayList<WriteBuffers.ByteSegmentRef>();
WriteBuffers.ByteSegmentRef byteSegmentRef = hashMapResult.first();
while (byteSegmentRef != null) {
results.add(hashMapResult.byteSegmentRef);
byteSegmentRef = hashMapResult.next();
}
dump.append(results.size()).append(" rows\n");
for (int i = 0; i < results.size(); ++i) {
WriteBuffers.ByteSegmentRef segment = results.get(i);
byteIntervals.put(
segment.getOffset(),
segment.getLength() + ((i == 0) ? 1 : 0)); // state byte in the first record
}
}
if (examined != keysAssigned) {
dump.append("Found " + examined + " keys!\n");
}
// Report suspicious gaps in writeBuffers
long currentOffset = 0;
for (Map.Entry<Long, Integer> e : byteIntervals.entrySet()) {
long start = e.getKey(), len = e.getValue();
if (start - currentOffset > 4) {
dump.append("Gap! [" + currentOffset + ", " + start + ")\n");
}
currentOffset = start + len;
}
LOG.info("Hashtable dump:\n " + dump.toString());
}
/** Same as {@link #isSameKey(long, int, long, int)} but for externally stored key. */
private boolean isSameKey(
byte[] key, int offset, int length, long ref, int hashCode, WriteBuffers.Position readPos) {
if (!compareHashBits(ref, hashCode)) {
return false; // Hash bits don't match.
}
writeBuffers.setReadPoint(getFirstRecordLengthsOffset(ref, readPos), readPos);
int valueLength = (int) writeBuffers.readVLong(readPos),
keyLength = (int) writeBuffers.readVLong(readPos);
long keyOffset = Ref.getOffset(ref) - (valueLength + keyLength);
// See the comment in the other isSameKey
if (offset == 0) {
return writeBuffers.isEqual(key, length, keyOffset, keyLength);
} else {
return writeBuffers.isEqual(key, offset, length, keyOffset, keyLength);
}
}
/**
* Verifies that the key matches a requisite key.
*
* @param cmpOffset The offset to the key to compare with.
* @param cmpLength The length of the key to compare with.
* @param ref The ref that can be used to retrieve the candidate key.
* @param hashCode
* @return -1 if the key referenced by ref is different than the one referenced by cmp... 0 if the
* keys match, and there's only one value for this key (no list). Offset if the keys match,
* and there are multiple values for this key (a list).
*/
private boolean isSameKey(long cmpOffset, int cmpLength, long ref, int hashCode) {
if (!compareHashBits(ref, hashCode)) {
return false; // Hash bits in ref don't match.
}
writeBuffers.setReadPoint(getFirstRecordLengthsOffset(ref, null));
int valueLength = (int) writeBuffers.readVLong(), keyLength = (int) writeBuffers.readVLong();
if (keyLength != cmpLength) {
return false;
}
long keyOffset = Ref.getOffset(ref) - (valueLength + keyLength);
// There's full hash code stored in front of the key. We could check that first. If keyLength
// is <= 4 it obviously doesn't make sense, less bytes to check in a key. Then, if there's a
// match, we check it in vain. But what is the proportion of matches? For writes it could be 0
// if all keys are unique, for reads we hope it's really high. Then if there's a mismatch what
// probability is there that key mismatches in <4 bytes (so just checking the key is faster)?
// We assume the latter is pretty high, so we don't check for now.
return writeBuffers.isEqual(cmpOffset, cmpLength, keyOffset, keyLength);
}
private void expandAndRehashImpl(long capacity) {
long expandTime = System.currentTimeMillis();
final long[] oldRefs = refs;
validateCapacity(capacity);
long[] newRefs = new long[(int) capacity];
// We store some hash bits in ref; for every expansion, we need to add one bit to hash.
// If we have enough bits, we'll do that; if we don't, we'll rehash.
// LOG.info("Expanding the hashtable to " + capacity + " capacity");
int newHashBitCount = hashBitCount + 1;
// Relocate all assigned slots from the old hash table.
int maxSteps = 0;
for (int oldSlot = 0; oldSlot < oldRefs.length; ++oldSlot) {
long oldRef = oldRefs[oldSlot];
if (oldRef == 0) {
continue;
}
// TODO: we could actually store a bit flag in ref indicating whether this is a hash
// match or a probe, and in the former case use hash bits (for a first few resizes).
// int hashCodeOrPart = oldSlot | Ref.getNthHashBit(oldRef, startingHashBitCount,
// newHashBitCount);
writeBuffers.setReadPoint(getFirstRecordLengthsOffset(oldRef, null));
// Read the value and key length for the first record.
int hashCode =
(int)
writeBuffers.readNByteLong(
Ref.getOffset(oldRef) - writeBuffers.readVLong() - writeBuffers.readVLong() - 4,
4);
int probeSteps = relocateKeyRef(newRefs, oldRef, hashCode);
maxSteps = Math.max(probeSteps, maxSteps);
}
this.refs = newRefs;
this.largestNumberOfSteps = maxSteps;
this.hashBitCount = newHashBitCount;
this.resizeThreshold = (int) (capacity * loadFactor);
metricExpandsMs += (System.currentTimeMillis() - expandTime);
++metricExpands;
}
