I'm testing Java driver with Agrona:0.9.1 and lmdbjava:0.6.3 and getting quite good lookup speed. Are there options to improve int => int map performance. My first attempt:

`

public class LMDBAgronaTest {
private static final String DB_NAME = "kv";
private static final long MAX_ENTRIES = 1_000_000;
private static final int ONE_K = 1_024;
private static final int MAX_ENTRY = 4 * ONE_K;

@rule
public final TemporaryFolder tmp = new TemporaryFolder();

// DB state
private Env env;
private Dbi db;
private MutableDirectBuffer key;
private MutableDirectBuffer val;

@before
public void setUp() throws IOException {
System.setProperty(Env.DISABLE_CHECKS_PROP, String.valueOf(true));
final File path = tmp.newFolder();
env = create(PROXY_DB)
.setMapSize(MAX_ENTRY * MAX_ENTRIES * 3)
.setMaxDbs(1)
.open(path, MDB_NOMETASYNC, MDB_NOSYNC);
db = env.openDbi(DB_NAME, MDB_CREATE);
key = new UnsafeBuffer(allocateDirect(4));
val = new UnsafeBuffer(allocateDirect(4));
}

@after
public void tearDown() {
out.println("Before close: " + new Date());
db.close();
env.close();
out.println("After close: " + new Date());
}

@test
public void nativeBuffersNoFlushOrderedKeys() {

// Write one by one
out.println("Begin insert: " + new Date());
for (int i = 0; i < MAX_ENTRIES; ++i) {
  val.putInt(0, i);
  key.putInt(0, i);
  db.put(key, val);
}

// Read one by one
out.println("Begin lookup: " + new Date());
final Txn<DirectBuffer> t = env.txnRead();
t.reset();
for (int i = 0; i < MAX_ENTRIES; ++i) {
  t.renew();
  key.putInt(0, i);
  final DirectBuffer result = db.get(t, key);
  assertNotNull(result);
  assertEquals(i, result.getInt(0));
  t.reset();
}

}
}

`

Begin insert: Fri Feb 15 12:26:40 AEDT 2019
Begin lookup: Fri Feb 15 12:27:05 AEDT 2019
Before close: Fri Feb 15 12:27:05 AEDT 2019
After close: Fri Feb 15 12:27:05 AEDT 2019

• How do you estimate map size? Looks like 4k * MAX_ENTRIES is not sufficient ..
• Is there best practice document for threading in java env.?
• Has someone experience in serializing using Kryo and storing in LMLDB Java (e.g. type of buffer selection)?

I'm total newbie in LMDB and advices would be very welcome. I'm trying gradually extend value to store bloated java objects instead of currently int.

Thanks
Pranas