CakePHP Paginate Sort on Contain Data - php

Question

It's a simple application for tracking user hobbies. A user can have many hobbies, which are organized into different hobby groups.
So I have 4 related tables: users, users_hobbies, hobbies, hobby_groups.
users is a has-and-belongs-to-many relation to hobbies, via the users_hobbies join table.
hobbies belongs-to a hobby_group, hobby_group has-many hobbies
Makes sense, pretty simple so far.
In UsersHobbiesController, I have:
$paginate = [
'contain' => [
'Hobby' => [
'fields' => ['id', 'name'],
'HobbyGroup' => [
'fields' => ['id', 'name']
]
]
]
];
Also, in my index() function, I build the pagination.
$usersHobbies = $this->paginate('UsersHobby');
$this->set(compact('usersHobbies));
When I access the $usersHobbies variable in my index.ctp View file, it has the data I want for building an output table. It looks like:
array(
(int) 0 => array(
'UsersHobby' => array(...),
'Hobby' => array(
'id' => 'abc-def-ghi',
'name' => 'Jet Skiing',
'HobbyGroup' => array(
'id' => 'oiuy-trew-qldf',
'name' => 'Watersports'
)
)
)
....
)
To sort the output table, I've added some sorting columns:
<th><?php echo $this->Paginator->sort('Hobby.name', 'Hobby'); ?></th>
<th><?php echo $this->Paginator->sort('Hobby.HobbyGroup.id', 'Hobby'); ?></th>
The first header works for sorting on the Hobby name. But I can't get the second header to sort for the HobbyGroup. Is there a simple way to do this?
I've searched for a few hours on StackOverflow, but can't seem to find an answer that works for me. Thanks.

Answer 1

This will not work as you expect because of how CakePHP fetches data.
Depending how you setup your relationships what will happen is that Cake will first select the Hobbies and then do another query for Hobby Groups.
So any sorting you apply to the second query will be generally useless and lost when that data is mapped to the list of Hobbies.
So you have
SELECT hobbies....
Then another select will be issued
SELECT hooby_groups WHERE hobby_id IN [list of ids ] ORDER BY hobby_groups_id
The data from the second select will be mapped to the first one, so your order by did not do much!
Depending on what CakePHP version you are using you can do a couple of things:
Define the relationship to use INNER JOIN strategy so will avoid creating two SELECT statements. This way the order by cause will sort all the data as you expect. The caveat is that with INNER JOIN Hobbies that do not have any group associated will never be selected by your pagination.
If you are using CakePHP 2.x you could have a look at Custom Query Pagination and build the query as you need it to be for it to work.
If you're using CakePHP 3.x you have a query builder there and the Paginator can paginate any query, so you can do you inner joins there.
To help you out you can use the DebugKit from CakePHP to see what actual queries are being run and how tweaking this and that parameter affects how the query is being generated. You will see where the order by is applied and why it may not work.
In CakePHP 2.x you can use type to control how the joining is done. You need to use INNER