{"id":223,"date":"2014-12-16T17:45:38","date_gmt":"2014-12-16T17:45:38","guid":{"rendered":"https:\/\/www.couchbase.com\/blog\/using-map-and-reduce-view-ranking\/"},"modified":"2014-12-16T17:45:38","modified_gmt":"2014-12-16T17:45:38","slug":"using-map-and-reduce-view-ranking","status":"publish","type":"post","link":"https:\/\/www.couchbase.com\/blog\/es\/using-map-and-reduce-view-ranking\/","title":{"rendered":"Using Map and Reduce View for Ranking"},"content":{"rendered":"

Starting from version 2.0, Couchbase server offers a powerful way of creating indexes for JSON documents through the concept of views.<\/span><\/b><\/p>\n\n\n\n

Using views, it is possible to define primary indexes, composite indexes and aggregations allowing to:<\/span><\/b><\/p>\n\n\n\n

. query documents on different JSON properties<\/span><\/b><\/p>\n\n\n\n

. create statistics and aggregates<\/span><\/b><\/p>\n\n\n\n

Views generate materialized indexes so provide a fast and efficient way for executing pre-defined queries.<\/span><\/b><\/p>\n\n\n\n

This blog provides a simple example of how a view using map and reduce can be created to index a JSON document attribute but also to determine document ranking based on that attribute.<\/span><\/b><\/p>\n\n\n\n

Using map and reduce is a very fast efficient way to determine ranking and can scale across million of users and provide very fast ranking lookup. Thanks <\/span>Aaron<\/span><\/a> for teaching me this!<\/span><\/b><\/p>\n\n\n\n

This can be used for instance for ranking users based on score or experience.<\/span><\/b><\/p>\n\n\n\n

This blog illustrates that concept for a user document with 2 attributes: name and experience, index this document based on experience and allow determining ranking based on the experience attribute.<\/span><\/b><\/p>\n\n\n\n


We will first write some Java code allowing connecting to Couchbase server and creating User documents. The following Java code is self-contained and will create the users.<\/span><\/b><\/p>\n\n\n\n

It is leveraging Gson Google code libraries for creating JSON objects.<\/span><\/b><\/p>\n\n\n\n

\u00a0<\/p>\n\n\n\n

package blog;<\/span><\/b><\/code><\/p>\n\n\n\n

import com.couchbase.client.CouchbaseClient;<\/span><\/b><\/code><\/p>\n\n\n\n

import com.couchbase.client.CouchbaseConnectionFactoryBuilder;<\/span><\/b><\/code><\/p>\n\n\n\n

import com.google.gson.Gson;<\/span><\/b><\/code><\/p>\n\n\n\n

import java.io.IOException;<\/span><\/b><\/code><\/p>\n\n\n\n

import java.io.UnsupportedEncodingException;<\/span><\/b><\/code><\/p>\n\n\n\n

import java.net.URI;<\/span><\/b><\/code><\/p>\n\n\n\n

import java.util.ArrayList;<\/span><\/b><\/code><\/p>\n\n\n\n

class UserDoc {<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0String name;<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0long experience;<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0UserDoc(String name, long experience) {<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0this.name = name;<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0this.experience = experience;<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0}<\/span><\/b><\/code><\/p>\n\n\n\n

}<\/span><\/b><\/code><\/p>\n\n\n\n

\/**<\/span><\/b><\/code><\/p>\n\n\n\n

*<\/span><\/b><\/code><\/p>\n\n\n\n

* @author alexis<\/span><\/b><\/code><\/p>\n\n\n\n

*\/<\/span><\/b><\/code><\/p>\n\n\n\n

public class RankView {<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0private static CouchbaseClient client;<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0public static void main(String[] args) throws UnsupportedEncodingException, IOException {<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0ArrayList nodes = new ArrayList();<\/uri><\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/ Add one or more nodes of your cluster (exchange the IP with yours)<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0nodes.add(URI.create(\"https:\/\/127.0.0.1:8091\/pools\"));<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/ Try to connect to the client<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0CouchbaseConnectionFactoryBuilder cfb = new CouchbaseConnectionFactoryBuilder();<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0cfb.setOpTimeout(10000);<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0cfb.setReadBufferSize(1024);<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0cfb.setShouldOptimize(true);<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0cfb.setTimeoutExceptionThreshold(100);<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0try {<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0client = new CouchbaseClient(cfb.buildCouchbaseConnection(nodes, \"default\", \"\"));<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0} catch (Exception e) {<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0System.err.println(\"Error connecting to Couchbase: \" + e.getMessage());<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0System.exit(1);<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0UserDoc user = null;<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/ Creates users<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0for (int i = 0; i <\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0user = new UserDoc(\"User\" + i, Math.round(Math.random()*1000));<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Gson json = new Gson();<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0String jsonString = json.toJson(user);<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0client.set(user.name, 0, jsonString);<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0client.shutdown();<\/span><\/b><\/code><\/p>\n\n\n\n

\u00a0\u00a0\u00a0}<\/span><\/b><\/code><\/p>\n\n\n\n

}<\/span><\/b><\/code><\/p>\n\n\n\n

After running this program (please change the URL or bucket name as appropriate) you should now have 10 users in your bucket.<\/b><\/p>\n\n\n\n

\u00a0<\/p>\n\n\n\n

<\/b><\/p>\n\n\n\n

The next step is to a User design document with a Rank view.<\/span><\/b><\/p>\n\n\n\n

The first step is create a simple Map for the Rank view which will emit the experience attribute:<\/span><\/b><\/p>\n\n\n\n

function (doc, meta) {<\/span><\/b><\/p>\n\n\n\n

\u00a0if (doc.experience)<\/span><\/b><\/p>\n\n\n\n

\u00a0 <\/span>emit(doc.experience, null);<\/span><\/b><\/p>\n\n\n\n

}<\/span><\/b><\/p>\n\n\n\n

Doing so will create an index based on experience attribute but will not allow to determine the ranking.<\/span><\/b><\/p>\n\n\n\n

This is where adding a Reduce fits in. We will add simple built-in _count reduce.<\/span><\/b><\/p>\n\n\n\n

The full view should look like this:<\/span><\/b><\/p>\n\n\n\n

<\/b><\/p>\n\n\n\n

The Reduce function allows to aggregate the number of User documents with a known experience value (if doc.experience).<\/span><\/b><\/p>\n\n\n\n

By not specifying any query parameter, it will output 10 which is the number of documents that we have created.<\/span><\/b><\/p>\n\n\n\n

In order to look up the ranking of a specific User what we need to do is first look up the ranking of a given user (User5 in this example):<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/ Look up a specific user<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0String jsonString = (String) client.get(“User5”);<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0user = json.fromJson(jsonString, UserDoc.class);<\/span><\/b><\/p>\n\n\n\n

From there, we can create a query which will filter this count with a range query with a descending order which will start by max value to capture all the users which have a greater experiencethe experience and end with value for the user:<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0View view = client.getView(“User”, “Rank”);<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Query query = new Query();<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0query.setIncludeDocs(true).setLimit(10000);<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0query.setRangeStart(Long.toString(Long.MAX_VALUE));<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0query.setRangeEnd(Long.toString(user.experience));<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0query.setDescending(true);<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0query.setReduce(true);<\/span><\/b><\/p>\n\n\n\n

As such the reduce will output the number of users which have a greater experience than the experience for that user. The ranking is simply that number + 1.<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0ViewResponse response = client.query(view, query);<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Iterator itr = response.iterator();<\/viewrow><\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0while (itr.hasNext()) {<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0ViewRow row = itr.next();<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0System.out.println(“Rank: ” + Long.parseLong(row.getValue()) + 1 );<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}<\/span><\/b><\/p>\n\n\n\n

This will output the Rank based on the experience for that user such as:<\/span><\/b><\/p>\n\n\n\n

Rank: 7<\/span><\/b><\/p>\n\n\n\n

The full Java code (again self contained) is:<\/span><\/b><\/p>\n\n\n\n

package blog;<\/span><\/b><\/p>\n\n\n\n

import com.couchbase.client.CouchbaseClient;<\/span><\/b><\/p>\n\n\n\n

import com.couchbase.client.CouchbaseConnectionFactoryBuilder;<\/span><\/b><\/p>\n\n\n\n

import com.couchbase.client.protocol.views.Query;<\/span><\/b><\/p>\n\n\n\n

import com.couchbase.client.protocol.views.View;<\/span><\/b><\/p>\n\n\n\n

import com.couchbase.client.protocol.views.ViewResponse;<\/span><\/b><\/p>\n\n\n\n

import com.couchbase.client.protocol.views.ViewRow;<\/span><\/b><\/p>\n\n\n\n

import com.google.gson.Gson;<\/span><\/b><\/p>\n\n\n\n

import java.io.IOException;<\/span><\/b><\/p>\n\n\n\n

import java.io.UnsupportedEncodingException;<\/span><\/b><\/p>\n\n\n\n

import java.net.URI;<\/span><\/b><\/p>\n\n\n\n

import java.util.ArrayList;<\/span><\/b><\/p>\n\n\n\n

import java.util.Iterator;<\/span><\/b><\/p>\n\n\n\n

class UserDoc {<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0String name;<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0long experience;<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0UserDoc(String name, long experience) {<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0this.name = name;<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0this.experience = experience;<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0}<\/span><\/b><\/p>\n\n\n\n

}<\/span><\/b><\/p>\n\n\n\n

\/**<\/span><\/b><\/p>\n\n\n\n

*<\/span><\/b><\/p>\n\n\n\n

* @author alexis<\/span><\/b><\/p>\n\n\n\n

*\/<\/span><\/b><\/p>\n\n\n\n

public class RankView {<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0private static CouchbaseClient client;<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0public static void main(String[] args) throws UnsupportedEncodingException, IOException {<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0ArrayList nodes = new ArrayList();<\/uri><\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/ Add one or more nodes of your cluster (exchange the IP with yours)<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0nodes.add(URI.create(“https:\/\/127.0.0.1:8091\/pools”));<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/ Try to connect to the client<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0CouchbaseConnectionFactoryBuilder cfb = new CouchbaseConnectionFactoryBuilder();<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0cfb.setOpTimeout(10000);<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0cfb.setReadBufferSize(1024);<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0cfb.setShouldOptimize(true);<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0cfb.setTimeoutExceptionThreshold(100);<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0try {<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0client = new CouchbaseClient(cfb.buildCouchbaseConnection(nodes, “default”, “”));<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0} catch (Exception e) {<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0System.err.println(“Error connecting to Couchbase: ” + e.getMessage());<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0System.exit(1);<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0UserDoc user = null;<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Gson json = null;<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/ Creates users<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0for (int i = 0; i <\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0user = new UserDoc(“User” + i, Math.round(Math.random() * 1000));<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0json = new Gson();<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0String jsonString = json.toJson(user);<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0client.set(user.name, 0, jsonString);<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/ Look up a specific user<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0String jsonString = (String) client.get(“User5”);<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0user = json.fromJson(jsonString, UserDoc.class);<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0View view = client.getView(“User”, “Rank”);<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Query query = new Query();<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0query.setIncludeDocs(true).setLimit(10000);<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0query.setRangeStart(Long.toString(Long.MAX_VALUE));<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0query.setRangeEnd(Long.toString(user.experience));<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0query.setDescending(true);<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0query.setReduce(true);<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0ViewResponse response = client.query(view, query);<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Iterator itr = response.iterator();<\/viewrow><\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0while (itr.hasNext()) {<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0ViewRow row = itr.next();<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0System.out.println(“Rank: ” + Long.parseLong(row.getValue()) + 1 );<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0client.shutdown();<\/span><\/b><\/p>\n\n\n\n

\u00a0\u00a0\u00a0}<\/span><\/b><\/p>\n\n\n\n

}<\/span><\/b><\/p>\n\n\n\n

Using a map and reduce view for ranking allows to quickly and very efficiently look up a rank without having to do additional processing on the client side.<\/span><\/b><\/p>\n\n\n\n

To learn more about views and queries in Couchbase, read: <\/span>https:\/\/www.couchbase.com\/docs\/couchbase-devguide-2.1.0\/indexing-querying-data.html<\/span><\/a><\/b><\/p>\n\n\n\n

For questions and comments: <\/span>alexis@couchbase.com<\/span><\/a> or @alexisroos on Twitter.<\/span><\/b><\/p>","protected":false},"excerpt":{"rendered":"

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