教条中的标准和缓存

Question

I have a doctrine entity called Site with the following field:

/**
 * @ORM\OneToMany(targetEntity="SiteAsset", mappedBy="site")
 */
protected $assets;

I also have a function for getting an element of $assets with a given value of its url field:

public function getAssetByUrl($url) {
    $c = Criteria::create()->
    where(Criteria::expr()->eq('url',$url));
    $matching = $this->assets->matching($c);
    return $matching[0];
}

This function behaves very strangely. It appears to work if I run it immediately after fetching the entity from the database. But after a few database operations have been queued up, it begins to fail. I know it is failing, as I can find the asset I want as follows:

public function getAssetByUrl($url) {
    foreach($this->assets as $asset) {
        if($asset->getUrl() === $url) {
            return $asset;
        }
    }
}

Furthermore, if I combine the two functions into:

public function getAssetByUrl($url) {
    foreach($this->assets as $asset) {
        if($asset->getUrl() === $url) {
            error_log('found');
        }
    }

    $c = Criteria::create()->
    where(Criteria::expr()->eq('url',$url));
    $matching = $this->assets->matching($c);
    error_log($matching[0] ? 'found' : 'not found');
    return $matching[0];
}

Then the Criteria always fails to find a match (i.e., when the function is called it always prints out 'found' followed by 'not found'). This would suggest that Doctrine is failing to find the entity I want in the case when it has already cached the entities in memory.

How can I ensure that matches are always found, while still making use of Doctrine's Criteria filtering system?

Answer 1

The issue was with the following line:

return $matching[0];

This returns the right answer if the PersistentCollection has not yet been fully fetched from the database. This is because the criteria is converted to an SQL query that returns an array containing only matching items; therefore getting the item at index 0 succeeds.

This returns the wrong answer if the PersistentCollection has already been fully fetched. This is because, internally, doctrine calls array_filter on the in-memory collection and returns the result. This means that the first element in the result is not necessarily at index 0, as array_filter preserves keys.

The solution was to wrap $matching in array_values($matching).