I use cakephp a lot and I have recently created a hierarchy of some 120,000 items, all neatly mapped with parent-child relationships but no MPTT data.  Cake’s inbuilt mechanism for converting adjacency list model to a modified preorder tree traversal (MPTT) model hierarchy was far to slow: on my PC and with this much data it was taking about a second per row, which adds up to an awfully long time to process the whole tree!

Given the need for this type of conversion I found it surprisingly difficult to find a script that the the Agency list to MPTT conversion, so I thought I’d document what I found here, and add to it if I find any further.

So, using the CakePHP naming conventions here is a script to convert Agency List to MPTT using MySQL and PHP.  This is much faster than the native CakePHP model->recover() method (which rebuilds your hierarchy) which is important on big datasets obviously.  This script is based on the function in this excellent article on MPTT.

//Make sure it doesn't time out
        set_time_limit (0);

	$con = mysql_connect("localhost","user","password");
	if (!$con){die('Could not connect: ' . mysql_error());}
	mysql_select_db("your_db", $con);

	function rebuild_tree($parent_id, $left) {
	   // the right value of this node is the left value + 1
	   $right = $left+1;   

	   // get all children of this node
	   $result = mysql_query('SELECT id FROM categories '.
	                          'WHERE parent_id="'.$parent_id.'";');   

	   while ($row = mysql_fetch_array($result)) {
	       // recursive execution of this function for each
	       // child of this node
	       // $right is the current right value, which is
	       // incremented by the rebuild_tree function
	       $right = rebuild_tree($row['id'], $right);
	   }   

	   // we've got the left value, and now that we've processed
	   // the children of this node we also know the right value
	   mysql_query('UPDATE categories SET lft='.$left.', rght='.
	                $right.' WHERE id="'.$parent_id.'";');   

	   // return the right value of this node + 1
	   return $right+1;
	}   

rebuild_tree('1',1);

mysql_close($con);

Using pure traditional SQL you can use the following script apparently, but I didn’t have time to make it work in MySQL and the above processed things quickly enough. The source of the script below is here http://data.bangtech.com/sql/nested_set_treeview.htm

-- Tree holds the adjacency model
CREATE TABLE Tree
(emp CHAR(10) NOT NULL,
 boss CHAR(10));

INSERT INTO Tree
SELECT emp, boss FROM Personnel;

-- Stack starts empty, will holds the nested set model
CREATE TABLE Stack
(stack_top INTEGER NOT NULL,
 emp CHAR(10) NOT NULL,
 lft INTEGER,
 rgt INTEGER);

BEGIN ATOMIC
DECLARE counter INTEGER;
DECLARE max_counter INTEGER;
DECLARE current_top INTEGER;

SET counter = 2;
SET max_counter = 2 * (SELECT COUNT(*) FROM Tree);
SET current_top = 1;

INSERT INTO Stack
SELECT 1, emp, 1, NULL
 FROM Tree
 WHERE boss IS NULL;

DELETE FROM Tree
 WHERE boss IS NULL;

WHILE counter <= (max_counter - 2)
LOOP IF EXISTS (SELECT *
 FROM Stack AS S1, Tree AS T1
 WHERE S1.emp = T1.boss
 AND S1.stack_top = current_top)
 THEN
 BEGIN -- push when top has subordinates, set lft value
 INSERT INTO Stack
 SELECT (current_top + 1), MIN(T1.emp), counter, NULL
 FROM Stack AS S1, Tree AS T1
 WHERE S1.emp = T1.boss
 AND S1.stack_top = current_top;

 DELETE FROM Tree
 WHERE emp = (SELECT emp
 FROM Stack
 WHERE stack_top = current_top + 1);

 SET counter = counter + 1;
 SET current_top = current_top + 1;
 END
 ELSE
 BEGIN -- pop the stack and set rgt value
 UPDATE Stack
 SET rgt = counter,
 stack_top = -stack_top -- pops the stack
 WHERE stack_top = current_top
 SET counter = counter + 1;
 SET current_top = current_top - 1;
 END IF;
 END LOOP;
END;

Check out the below, they’re required viewing as far as I’m concerned for potential Facebook App developers.

Anatomy of a Facebook Application (JayGoldman, Radiant Core)

FBML Overview (Sunil Boodram, Trapeze Media)

FQL Overview (Craig Saila)

Tonight while trying to workout some functionality related to web services I found I needed to delve into the data being retrieved,  the need for the ever handy CFDUMP came to mind.  A look around showed that there doesn’t appear to be anything as user friendly as CFdump in Flex, but I cam across this article on ObjectUtil.

Basically you can use the ObjectUtil class to dump trace data (including complex objects) to the debug window thus:

<mx:Script>

<![CDATA[

import mx.rpc.events.ResultEvent;

import mx.managers.PopUpManager;

import mx.utils.ObjectUtil;

private function remotingCFCHandler(e:ResultEvent):void

{

//Dump the result of a call to a webservice

trace( ObjectUtil.toString( e.result ) );

}

]]>

</mx:Script>

Which will while not quite CFDUMP will provide you (hopefully) with enough data to move past your problem.

Testing a few combinations the on

<a href=”/users/logout” onclick=”FB.Connect.logout(logoutCallback())”>Logout</a>

(who’s logic I found here http://developers.facebook.com/docs/?u=facebook.jslib.FB.Connect.logout)

simply didn’t work.  The function was called as was the callback but it simply didn’t log out of Facebook.

The only way I could get it to work was using the logoutAndRedirect function instead, using the following:

<a href=”#” onclick=”FB.Connect.logoutAndRedirect(‘/users/logout’)”>Logout</a>

NOTE: Originally I had put a value in the href attribute (“/users/logout” thinking it would degrade nicely) but this stopped the main function from working, so as far as I can tell you must have a # symbol in the href.

Ok so consider the following:

<CFFUNCTION name=”getByCriteria” access=”public” returntype=”query” output=”false” displayname=”" hint=”">
<CFARGUMENT name=”child_ocl_id” required=”false” >

This will result in an explicitly set variable that is set to “undefined” – the cfdump is thus:

Note the explicitly “undefined” status as well as (what my code was expecting) the “[empty string]” status

This stays the same whether you add a cfparam later or not, thus:

<CFFUNCTION name=”getByCriteria” access=”public” returntype=”query” output=”false” displayname=”" hint=”">
<CFARGUMENT name=”child_ocl_id” required=”false” >
<CFPARAM name=”arguments.child_ocl_id” default=”my new default” >

Note the above example isn’t what was in my code! It’s just a simple explanation of the behaviour I noticed. So just something to be aware of if you get unexplained “undefined” errors in your migration to Coldfusion 9.

$fbsessionid = $this->facebook->api_client->session_key;

This will NOT work

echo ='My line with a line feed \n';

This WILL work

echo ="My line with a line feed \n";

The latest of these that I have implemented successfully is an excellent implementation of DaisyDiff by Daniel Mackey.  Though he has put together a direct Java jar implementation I have opted for his CFX_CompareHTML implementation because of it’s support for UTF-8 characters, he sent it on to me directly the last time I checked it wasn’t available on line (thanks Dan).

The free CFX_compareHTML does a DIFF analyses on formatted html, and then displays it as a combined diff output, this is useful for comparing before and after content for example and is comparable to tools such as (the very expensive) diffdoc.  Diffdoc costs about $4000 for a server license, and while it has more applications (i.e. as a desktop tool) for web based html comparison CFX_CompareHTML is more than adequate.

Once installed (the one downside of CFX tags is of course the need to install them and set their path in CF admin) it’s as simple as:

<cfx_CompareHTML left=“Some HTML content” right=“Some more HTML Content”>

Produces the following (nicked from CFDan.com – hope that’s ok Dan?!)

As I mentioned there are a couple of great tags/components in the CF open source world that I’ve used lately, and inspired by this excellent work I’ll be documenting them over the coming days.

In my case it turned out to be a number of issues (a missing file and a missing database table) but the process to identify and therefore fix the problem is:

1. Make sure you set up your DATABASE_CONFIG is setup correctly (database.php)
2. Check that your tmp folder (and all of it’s sub folders) are writable (at least chmod 666 on Linux),
3. While you’re there delete all cache files from allof the tmp sub folders

 After that, if you’re still having “Error: The requested address “/” was not found on this server” then you’re likely to be missing a database table or an include file, so go into your core.php and set:

Configure::write('debug', 2);

This should reveal any remaining issues.

One of the things that I found most confusing about implementing the Auth component and ACL was their precise relationship, how they hung together, what one was and the other wasn’t or more specifically what one did and the other didn’t.

While conceptually not complicated – the Auth Component is something that identifies a user whereas the ACL component is something that takes that knowledge and says “what does this identified user have access to” – they seem (at first) so intermeshed in the “Automagic” functions of CakePHP that it can be difficult to establish what is causing what to happen.

I found this particularly so when, having not gone through the Simple-Acl-controlled-Application tutorial kindly provided by the CakePHP team, I dropped the Auth component into my components list and lo and behold I was required to authenticate against actions I had wanted protected.

It wasn’t until reading this article and doing a bit of experimenting i realised that while it was definitely “Authenticating” it was not “Checking access” so none of my ACL stuff was kicking in at all.

An example of how the two functions seem intermeshed is the allowedActions function that is specified in the beforeFilter:

$this->Auth->allowedActions = array(‘*’);

This is (as the method path shows) a function of the Auth component, but it relates to Access, in this case the actions of the controller.  This is an important function to understand, this tells the AuthComponent to allow PUBLIC access to all actions, you can of course provide a specific array of actions here as well.  The important thing to understand is that “public” is just a default state given to a non authenticated user, it is not a specific group you need to create and assign by default (which is the case in some authentication systems I’ve seen).

So remember that while a user can be “authenticated” that is, they are known to the system they are not necessarily being  checked against their access profile,  $this->Auth->allowedActions can confuse matters if you’re not careful because it can suggest that the authenticated person does or doesn’t have access to something (because they get redirected to the login page).

When working out what is tripping up a security response, use this handy guide to Debugging CakePHP Auth component which can tell you what is being validated against and thus if it is your dodgy ACL setup or just the default settings in the Auth component that are causing any problems.