Hej folks! Again and again we have to interact with a kdb+ and kdb+tick. The guys from KX Systems provide us c.java to interact with their product. You might experienced that c.java is not really using an object oriented style (because q does not?), so we started to write our own wrapper and called it java-q. Feel free to create Issues if something is missing for you. And now: have fun:)
You do not need to be a q god to use this library!
We encapsulate all the q stuff for you! It's just simple Java. Look at the following example. Have you ever seen a q-sql select so Java pretty?
Select select = trade.select()
.column(size.sum())
.column(price.avg())
.group(sym.group())
.group(time.xbar(LongValue.from(60000L)))
.filter(sym.filterIn(SymbolValue.froms(new String[] {"AAA", "BBB"})))
.order(Direction.descending, time)
.build();Your schema is defined by code not by text! You get easy refactoring and lesser typos for free:)
Learn more about how to define your schema with a few lines of code.
public class MyTable extends ATable {
private static MyTable INSTANCE = new MyTable();
public static MyTable get() {
return INSTANCE;
}
public TimeColumn time = new TimeColumn("time");
public SymbolColumn sym = new SymbolColumn("sym");
public FloatColumn price = new FloatColumn("price");
public IntegerColumn size = new IntegerColumn("size");
private MyTable() {
super("mytable");
this.addColumn(this.time);
this.addColumn(this.sym);
this.addColumn(this.price);
this.addColumn(this.size);
}
}Learn more about how to create a q query.
// get table schema
MyTable table = MyTable.get();
// create select query
Select select = table.select()
.column(table.size.sum())
.column(table.price.avg())
.group(table.sym.group())
.filter(table.sym.filterIn(SymbolValue.froms(new String[] {"AAA", "BBB"})))
.order(Direction.descending, table.time)
.build();
System.out.println("q: " + select.toQ());
// connect to kdb+
QConnectorSync kx = QConnectorFactory.create("localhost", 5011);
kx.connect();
// execute select query and print the result
Result result = kx.select(select);
for (TableRow row : table.read(result)) {
System.out.println(row.get(table.time));
System.out.println(row.get(table.sym));
System.out.println(row.get(table.price));
System.out.println(row.get(table.size));
}
// close connection
kx.disconnect();Learn more about how to subscribe to q kdb+tick environement.