diff --git a/src/database/level/sorted.js b/src/database/level/sorted.js
index d262af89c2..115409cae8 100644
--- a/src/database/level/sorted.js
+++ b/src/database/level/sorted.js
@@ -151,6 +151,14 @@ module.exports = function(db, module) {
 		});
 	};
 
+	module.sortedSetsRanks = function(keys, values, callback) {
+		throw new Error('not implemented');
+	};
+
+	module.sortedSetRanks = function(key, values, callback) {
+		throw new Error('not implemented');
+	};
+
 	module.sortedSetRevRank = function(key, value, callback) {
 		module.getListRange(key, 0, -1, function(err, list) {
 			for (var i = list.length - 1, ii=0; i > ii; i--) {
diff --git a/src/database/mongo/sorted.js b/src/database/mongo/sorted.js
index 1f95ba2448..577ed9d2d1 100644
--- a/src/database/mongo/sorted.js
+++ b/src/database/mongo/sorted.js
@@ -264,6 +264,21 @@ module.exports = function(db, module) {
 		}, callback);
 	};
 
+	module.sortedSetRanks = function(key, values, callback) {
+		module.getSortedSetRange(key, 0, -1, function(err, sortedSet) {
+			if (err) {
+				return callback(err);
+			}
+
+			var result = values.map(function(value) {
+				var index = sortedSet.indexOf(value.toString());
+				return index !== -1 ? index : null;
+			});
+
+			callback(null, result);
+		});
+	};
+
 	module.sortedSetScore = function(key, value, callback) {
 		if (!key) {
 			return callback();
diff --git a/src/database/redis/sorted.js b/src/database/redis/sorted.js
index 2df108cf9b..4a9974cd9f 100644
--- a/src/database/redis/sorted.js
+++ b/src/database/redis/sorted.js
@@ -129,6 +129,14 @@ module.exports = function(redisClient, module) {
 		multi.exec(callback);
 	};
 
+	module.sortedSetRanks = function(key, values, callback) {
+		var multi = redisClient.multi();
+		for(var i=0; i<values.length; ++i) {
+			multi.zrank(key, values[i]);
+		}
+		multi.exec(callback);
+	};
+
 	module.sortedSetRevRank = function(key, value, callback) {
 		redisClient.zrevrank(key, value, callback);
 	};
diff --git a/src/posts.js b/src/posts.js
index dcedf4383d..b5b24208b2 100644
--- a/src/posts.js
+++ b/src/posts.js
@@ -4,6 +4,7 @@ var async = require('async'),
 	path = require('path'),
 	fs = require('fs'),
 	nconf = require('nconf'),
+	_ = require('underscore'),
 	validator = require('validator'),
 	winston = require('winston'),
 	gravatar = require('gravatar'),
@@ -534,24 +535,29 @@ var async = require('async'),
 		if (!Array.isArray(posts) || !posts.length) {
 			return callback(null, []);
 		}
+
 		user.getSettings(uid, function(err, settings) {
 			if (err) {
 				return callback(err);
 			}
+
 			var byVotes = settings.topicPostSort === 'most_votes';
 			var sets = posts.map(function(post) {
-				if (byVotes) {
-					return 'tid:' + post.tid + ':posts:votes';
-				} else {
-					return 'tid:' + post.tid + ':posts';
-				}
+				return byVotes ? 'tid:' + post.tid + ':posts:votes' : 'tid:' + post.tid + ':posts';
 			});
 
+			var uniqueSets = _.uniq(sets);
+			var method = 'sortedSetsRanks';
+			if (uniqueSets.length === 1) {
+				method = 'sortedSetRanks';
+				sets = uniqueSets[0];
+			}
+
 			var pids = posts.map(function(post) {
 				return post.pid;
 			});
 
-			db.sortedSetsRanks(sets, pids, function(err, indices) {
+			db[method](sets, pids, function(err, indices) {
 				if (err) {
 					return callback(err);
 				}