Voldemort Sets

voldemort-sets is a collection of view classes which allow for the efficient storage of sets of numbers in the Voldemort distributed key/value store.

Requirements

voldemort-sets requires Voldemort 0.60.

Installation

Place the provided JAR file (available in the downloads section) in the lib directory of your Voldemort install on each node.

Reboot your cluster.

Configuration

Add a view to your stores.xml configuration file:

<view>
  <name>sets</name>
  <view-of>raw-sets</view-of>
  <view-class>
    com.codahale.voldemort.sets.LongSet
  </view-class>
  <value-serializer>
    <type>string</type>
  </value-serializer>
</view>

The <name> element determines how your client will interface with the view.

The <view-of> element is the name of a defined store in which the serialized sets will be stored. The backing store's <value-serializer> should be identity, as the sets are stored in a compressed binary format.

The <view-class> element can refer to one of the following:

• com.codahale.voldemort.sets.LongSet: An unordered set of 64-bit integers. The integers are stored using Avro's variable-length zig-zag which reduces the amount of disk space used and the amount of disk I/O during reading and writing.
• com.codahale.voldemort.sets.SortedLongSet: A set of 64-bit integers, stored in ascending order using the same storage scheme as LongSet.
• com.codahale.voldemort.sets.ReverseSortedLongSet: A set of 64-bit integers, stored in descending order using the same storage scheme as LongSet.
• com.codahale.voldemort.sets.DoubleSet: An unordered set of 64-bit floating-point numbers. The numbers are stored as fixed-length, 8-byte blocks.
• com.codahale.voldemort.sets.SortedDoubleSet: A set of 64-bit floating-point numbers, stored in ascending order using the same storage scheme as DoubleSet.
• com.codahale.voldemort.sets.ReverseSortedDoubleSet: A set of 64-bit floating-point numbers, stored in descending order using the same storage scheme as DoubleSet.

The <value-serializer>'s <type> element should be string.

Usage

import voldemort.client.*;

public class SetOperationsExample {
    public void main(String[] args) throws Exception {
        final ClientConfig config = new ClientConfig().setBootstrapUrls(args[0]);
        final SocketStoreClientFactory factory = new SocketStoreClientFactory(config);
        final StoreClient<String, String> client = factory.getStoreClient("sets");
        
        client.get("evens"); // set doesn't exist, returns null
        
        client.put("evens", "ADD 2"); // adds 2 to the set
        
        client.get("evens"); // returns "2"
        
        client.put("evens", "ADD 2, 4, 6, 8"); // adds 4, 6, and 8 to the set
        
        client.get("evens"); // returns "2,4,6,8"
        
        client.put("evens", "REM 2"); // removes 2 from the set
        
        client.get("evens"); // returns "4,6,8"
        
        client.put("evens", "REM 4, 6"); // removes 4 and 6 from the set
        
        client.get("evens"); // returns "8"
    }
}

License

Copyright (c) 2009 Coda Hale, licensed to all under the terms of the MIT License.