IMap has no deleteAll(Set<k> keys) ? ... but has getAll() and putAll()

[Rob Bygrave]

So from a performance perspective I'd like to see and use a IMap.deleteAll( Set<k> keys).

It seems like an odd omission from the IMap API given that there is a getAll() and putAll().  So the fallback it to iterate the keys and call delete() on each one.  I see this was raised a few years ago: https://groups.google.com/forum/#!searchin/hazelcast/IMAP$20deleteall|sort:date/hazelcast/RC087UTMeq8/qM_k66-MO3AJ

Any reason why there is no deleteAll() ?

Thanks, Rob.

[Ahmet Mircik]

Hi,

You can do deletes in batches without a deleteAll method. Below is a simple example to demonstrate 2 ways of doing delete-all. I'm using version 3.9.2.

import com.hazelcast.core.Hazelcast;
import com.hazelcast.core.HazelcastInstance;
import com.hazelcast.core.IMap;
import com.hazelcast.query.EntryObject;
import com.hazelcast.query.PredicateBuilder;

import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import static java.util.Arrays.asList;

public class DeleteAll {

    public static void main(String[] args) {
        HazelcastInstance node = Hazelcast.newHazelcastInstance();
        IMap<Integer, Integer> map = node.getMap("test");

        map.put(1, 1);
        map.put(2, 2);
        map.put(3, 3);

        deleteAllWithEntryProcessor(map);
        // deleteAllWithPredicate(map);

        int size = map.size();
        if (size != 0) {
            throw new AssertionError("Expected size is zero but found :" + size);
        }

        System.out.println("Map size is :" + size);

    }

    private static void deleteAllWithEntryProcessor(IMap<Integer, Integer> map) {
        map.executeOnKeys(new HashSet<Integer>(asList(1, 2, 3)), new DeleteKeys());
    }

    public static final class DeleteKeys extends AbstractEntryProcessor<Integer, Integer> {
        @Override
        public Object process(Map.Entry<Integer, Integer> entry) {
            return entry.setValue(null);
        }
    }

    private static void deleteAllWithPredicate(IMap<Integer, Integer> map) {
        PredicateBuilder predicateBuilder = new PredicateBuilder();
        EntryObject entryObject = predicateBuilder.getEntryObject();

        List<Integer> keysToRemove = asList(1, 2, 3);
        Iterator<Integer> iterator = keysToRemove.iterator();

        boolean isFirstKey = true;
        while (iterator.hasNext()) {
            Integer key = iterator.next();

            if (isFirstKey) {
                isFirstKey = false;
                predicateBuilder = entryObject.key().equal(key);
            } else {
                predicateBuilder.or(entryObject.key().equal(key));
            }
        }

        map.removeAll(predicateBuilder);
    }
}

​

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[Rob Bygrave]

Thanks !!

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