How to use

openCursor

method

in

jetbrains.exodus.env.Store

@Override
public CloseableIterator<KVPair> getRange(byte[] minKey, byte[] maxKey, boolean reverse) {
  Preconditions.checkState(!this.closed.get(), "transaction closed");
  return new XodusIter(this.store.openCursor(this.tx), minKey, maxKey, reverse);
}

InnerIterator( final LocalDB.DB db )
{
  this.transaction = environment.beginReadonlyTransaction();
  this.cursor = getStore( db ).openCursor( transaction );
  doNext();
}

@Benchmark
public void readCrc(final Reader r, final Blackhole bh) {
 r.crc.reset();
 try (Cursor c = r.store.openCursor(r.tx)) {
  while (c.getNext()) {
   r.crc.update(c.getKey().getBytesUnsafe(), 0, r.keySize);
   r.crc.update(c.getValue().getBytesUnsafe(), 0, r.valSize);
  }
 }
 bh.consume(r.crc.getValue());
}

@Override
public void removeRange(byte[] minKey, byte[] maxKey) {
  Preconditions.checkState(!this.closed.get(), "transaction closed");
  Preconditions.checkState(!this.txType.isReadOnly(), "read-only transaction");
  try (final Cursor cursor = this.store.openCursor(this.tx)) {
    boolean found = minKey != null && minKey.length > 0 ?
     cursor.getSearchKeyRange(new ArrayByteIterable(minKey)) != null : cursor.getNext();
    while (found) {
      if (maxKey != null && ByteUtil.compare(XodusKVStore.get(cursor.getKey(), false), maxKey) >= 0)
        break;
      cursor.deleteCurrent();
      found = cursor.getNext();
    }
  }
}

@Benchmark
public void readSeq(final Reader r, final Blackhole bh) {
 try (Cursor c = r.store.openCursor(r.tx)) {
  while (c.getNext()) {
   bh.consume(c.getValue().getBytesUnsafe());
  }
 }
}

@Override
public KVPair getAtLeast(byte[] minKey, byte[] maxKey) {
  Preconditions.checkState(!this.closed.get(), "transaction closed");
  try (final Cursor cursor = this.store.openCursor(this.tx)) {
    final boolean found = minKey != null && minKey.length > 0 ?
     cursor.getSearchKeyRange(new ArrayByteIterable(minKey)) != null : cursor.getNext();
    if (!found)
      return null;
    final byte[] key = XodusKVStore.get(cursor.getKey(), true);
    if (maxKey != null && ByteUtil.compare(key, maxKey) >= 0)
      return null;
    return new KVPair(key, XodusKVStore.get(cursor.getValue(), true));
  }
}

@Benchmark
public void readRev(final Reader r, final Blackhole bh) {
 try (Cursor c = r.store.openCursor(r.tx)) {
  c.getLast();
  do {
   bh.consume(c.getValue().getBytesUnsafe());
  } while (c.getPrev());
 }
}

@Override
public KVPair getAtMost(byte[] maxKey, byte[] minKey) {
  Preconditions.checkState(!this.closed.get(), "transaction closed");
  try (final Cursor cursor = this.store.openCursor(this.tx)) {
    // It's possible somebody could be simultaneously inserting keys just after maxKey, in which case we
    // could be tricked into returning a key > maxKey. This is unlikely, but make sure it can't affect us.
    while (true) {
      if (maxKey != null)
        cursor.getSearchKeyRange(new ArrayByteIterable(maxKey));
      if (!cursor.getPrev())
        return null;
      final byte[] key = XodusKVStore.get(cursor.getKey(), true);
      if (maxKey != null && ByteUtil.compare(key, maxKey) >= 0)
        continue;
      if (minKey != null && ByteUtil.compare(key, minKey) < 0)
        return null;
      return new KVPair(key, XodusKVStore.get(cursor.getValue(), true));
    }
  }
}

@Benchmark
public void readXxh64(final Reader r, final Blackhole bh) {
 long result = 0;
 try (Cursor c = r.store.openCursor(r.tx)) {
  while (c.getNext()) {
   result += xx_r39().hashBytes(c.getKey().getBytesUnsafe(), 0, r.keySize);
   result += xx_r39().
     hashBytes(c.getValue().getBytesUnsafe(), 0, r.valSize);
  }
 }
 bh.consume(result);
}