What function in Social Graph loads mutual friends so fast?

Question

I am making a Facebook application for which I require the mutual friends of the logged in user. The Old API friends.getMutualFriends does the work but it is very slow. I was wondering if there is any other way of getting the list of mutual friends.

Moreover, applications like SocialGraph load very fast, so what functions are they using to get hold of the mutual friends so quickly?

Answer 1

If you are concerned about speed, I would suggest calling the information once and finding a way to cache the data. Facebook now provides you with the ability to do so "legally". You may use memcached for this sort of thing or save it temporarily in a database.

Answer 2

I found the solution :)
With friends.getMutualFriends, it takes n^3 API which is a huge number. I tried areFriends as well which was no better. So I fetched the data via FQL query as follows:

//Create Query
$params = array(
    'method' => 'fql.query',
    'query' => "  SELECT uid1, uid2 FROM friend 
WHERE uid1 IN 
(SELECT uid2 FROM friend WHERE uid1= $match)
AND uid2 IN 
(SELECT uid2 FROM friend WHERE uid1= $match)",
);

//Run Query
$result = $facebook->api($params);

It takes less than a second to get the mutual friends !

Answer 3

As of September 2011, there is a new api call for this:

This week we added a connection for the User object that allows you to get the list of mutual friends between two users. To use it, just get an access token for the current user and issue a GET request to:

https://graph.facebook.com/me/mutualfriends/FRIEND_ID

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