Installation
<dependency>
<groupId>com.nfsdb</groupId>
<artifactId>nfsdb-core</artifactId>
<version>2.0.1</version>
</dependency>Change log
- #10 Support for sublasses
- #16 Fixed defect in BulkWriter that could cause index data loss
- Reader creates new journal if one does not exist instead of throwing exception.
- #15 Unique key support
- #4 Data increment processing
Unique key support
Unique keys can be either String or int fields. In fact it is just an indexed field that you can search.
Configure int "id" field as follows:
JournalFactory factory = new JournalFactory(new JournalConfigurationBuilder() {{
$(Order.class)
.$int("id").index()
// or .$str("id).index() for String keys
;
}}.build(args[0]));To prepare for search by "id" create parameterisable query stream. It is analogous to PreparedStatement.
Journal<Order> reader = factory.reader(Order.class);
Order order = new Order();
Q q = new QImpl();
StringRef col = new StringRef();
col.value = "id";
IntRef id = new IntRef();
DataSource<Order> ds = q.ds(
q.forEachPartition(
q.sourceDesc(reader)
, q.headEquals(col, id)
)
, order
);Execute query for given "id":
id.value = i;
Order o = ds.$new().head();Data increment processing
On client have a reader for journal that is being replicated. increment() and incrementBuffered() create iterator over added data.
This is fully featured client that measures transaction latency.
public static void main(String[] args) throws Exception {
JournalFactory factory = new JournalFactory(args[0]);
final JournalClient client = new JournalClient(factory);
final Journal<Price> reader = factory.bulkReader(Price.class, "price-copy");
client.subscribe(Price.class, null, "price-copy", new TxListener() {
@Override
public void onCommit() {
int count = 0;
long t = 0;
for (Price p : reader.incrementBuffered()) {
if (count == 0) {
t = p.getTimestamp();
}
count++;
}
System.out.println("took: "
+ (System.currentTimeMillis() - t)
+ ", count=" + count);
}
});
client.start();
System.out.println("Client started");
}