CakePHP’s invisible query cache

I just wanted to document something that was driving me nuts in Cake PHP.

I do a simple find on a model:

$thing = $this->Model->find(array('id' => 123), NULL, NULL, 1);

Then later on, I make the same query again. Only the first query appears in the SQL debug output. Why call it again? Well, I’ve made some manual queries in between the calls using SQL that is inconvenient to emulate in Cake functions, in particular INSERT IGNORE. It turns out that Cake has a largely undocumented query cache, but Cake has no idea that its cache is dirty because of the manual queries. The _clearCache function is not yet implemented for the query cache, so the only choice is to disable it before the first query, and you can do that during a single instantiation by saying:

$this->Model->cacheQueries = false;

Note that the query has 1 level of recursion, which means that all the sub-queries are also cached. Setting cacheQueries to false on this one model means that all queries through it don’t get cached, including those that may be in other models via relationships.

CakePHP hasManyAndBelongsTo relationship limitations

Cake has some nice support for modeling many to many relations using ‘hasManyAndBelongsTo’. There’s a simple example here.
Though this works well for simple connections between classes, you can’t do much else. Taking the classic Blog-style Posts and Tags example, this approach will easily let you link multiple tags to multiple posts. But what if you want to track the date that a tag was applied to a post? If you add a date field to the join table, it seems pretty much impossible to retrieve it, and setting it is even harder. You can search on it by twiddling with the conditions on the relation, but that’s ugly. I think in that case, you have no option but to model the relation explicitly with two pairs of hasMany/belongsTo relations linked through a PostTag model, and then you’ll have to set your recursion deeper and get busy with unbindmodel in order to keep the number of queries down. Who knows, I might even write up an example and post it here…