Loading models eagerly

[leofeyer]

Now that @fritzmg has debugged the memory issues caused by eagerly loaded models, I want to discuss eager loading in general. Take this code for example:

calendar-bundle/src/Resources/contao/classes/Events.php

Lines 427 to 434 in 7bd32ae

	// Link to an article
	case 'article':
	if (($objArticle = \ArticleModel::findByPk($objEvent->articleId, array('eager'=>true))) !== null && ($objPid = $objArticle->getRelated('pid')) instanceof PageModel)
	{
	/** @var PageModel $objPid */
	self::$arrUrlCache[$strCacheKey] = ampersand($objPid->getFrontendUrl('/articles/' . ($objArticle->alias ?: $objArticle->id)));
	}
	break;

With array('eager'=>true) we instruct Contao to also load all related models. Here's what we get:

• ArticleModel
• PageModel (pid)
• UserModel (author)

However, we are not using the UserModel in this case, so we would not have needed to create it. On the other hand, using array('eager'=>true) has saved us one additional database query.

@contao/developers Would you prefer having more database queries and no unneeded models over having less database queries and potentially unneeded models?

[leofeyer]

As discussed in Mumble on July 5th, we should generally disable eager loading in DCAs ('load'=>'eager') and never load collections eagerly. In other cases like above, it might be helpful.

[leofeyer]

Changed where applicable (see commits above).