CakePHP: Number of Users with Posts or Pages tagged with a given Tag

Question

We have the following relationship for our data:

Users

• Have and belong to many Pages
• Have and belong to many Posts

Pages

• Have and belong to many Users
• Have and belong to many Tags

Posts

• Have and belong to many Users
• Have and belong to many Tags

Tags

• Have and belong to many Pages
• Have and belong to many Posts

Here is our question: Is there a way to get just a count of how many unique Users have ever created either a Page or Post that has been tagged with a given Tag?

In our Tag model:

function getSupportingUserCount($tag_id)
{
    $user_count = $this->find(?);
    return $user_count;
}

Answer 1

You can just avoid joins that may be slow if you've got many rows. So first get the tagid, then search for that id via the User model associations.

$tag = $this->Tag->find('first', array('conditions'  => array('Tag.name' => 'blahblah'), 'recursive'  => -1);
$tag_id = $tag['Tag']['id'];
$this->User->find('count', array('conditions'  => "OR" => array (
    array('Page.tag_id'  => $tag_id,
          'Post.tag_id'  => $tag_id )
));

(untested code so there may be typos)

(aside: are you sure each Post has many users? usually a post has only 1 author)