Indices and Comparable<T>: not documented

[otaconix]

Indices get explained in the Hazelcast documentation. However, it fails to mention that every indexed property type needs to be of a subtype of Comparable. Putting an index on a non-comparable type results in runtime ClassCastExceptions.

Please make this explicit in the documentation!

Sample code to demonstrate the problem:

import java.io.Serializable;

import com.hazelcast.config.Config;
import com.hazelcast.config.MapConfig;
import com.hazelcast.config.MapIndexConfig;
import com.hazelcast.core.Hazelcast;
import com.hazelcast.core.HazelcastInstance;
import com.hazelcast.core.IMap;

public class MainClass {

    private static final String MAP_NAME = "mymap";

    public static void main(String[] args) {
        HazelcastInstance instance = Hazelcast.newHazelcastInstance();
        Config config = instance.getConfig();
        MapConfig mapConfig = config.getMapConfig(MAP_NAME);
        mapConfig.addMapIndexConfig(new MapIndexConfig("other", true)); // Also happens on unordered indexes

        IMap<NonComparable, Object> testMap = instance.getMap(MAP_NAME);
        NonComparable other = new NonComparable(null);

        testMap.put(new NonComparable(other), new NonComparable(other));

        instance.shutdown();
    }

    private static class NonComparable implements Serializable {

        NonComparable other;

        public NonComparable(NonComparable other) {
            this.other = other;
        }
    }
}

[Serdaro]

A note added to the Indexing section under Distributed Query. It reads: "Non-primitive types to be indexed should implement Comparable".

[pveentjer]

Very strange there is a dependency on Comparable for an unordered index.