Magento 1.9 – Get Ordered Items from Last 10 Days for Specific Customer

For anyone stumbling over this in the future, I've gone for the following code as the most (to me) sensible version:

$collection = Mage::getResourceModel('sales/order_item_collection');
$collection->getSelect()->reset(Zend_Db_Select::COLUMNS)
    ->columns(array('SUM(qty_ordered) as order_quantity'))
    ->where(sprintf("product_id = %s", $row->getProductId()))
    ->where(sprintf('created_at > "%s" AND created_at < "%s"', $week["from"], $week["to"]));

I'm yet to figure out if it would be quicker to grab all my date ranges at once and work through them in PHP, or if it's quicker like this creating a separate block for each week.

I found out that ORDER BY RAND() is very unperformant on a Magento collection because all data gets copied to a temp table, assigned a random number and then sorted without index. If we reduce the data to be copied to just the ID, it gets a lot faster (still not perfect because the slow sorting remains but OK for a small catalog like yours).

For this, I made a modified version of getAllIds():

$numberOfItems = 5;

// Step 1: Preselect ids using ORDER BY RAND()
// Filters are applied here
$productCollection = Mage::getModel('catalog/product')
    ->getCollection();
$productCollection
    ->addStoreFilter()
    ->setVisibility(Mage::getSingleton('catalog/product_visibility')->getVisibleInCatalogIds());
$productCollection->getSelect()->order('RAND()');
$idsSelect = clone $productCollection->getSelect();
$idsSelect->reset(Zend_Db_Select::LIMIT_COUNT);
$idsSelect->reset(Zend_Db_Select::LIMIT_OFFSET);
$idsSelect->reset(Zend_Db_Select::COLUMNS);
$idsSelect->columns('e.' . $productCollection->getEntity()->getIdFieldName());
$idsSelect->limit($numberOfItems, null);
$idsSelect->resetJoinLeft();
$accessor = new ReflectionObject($productCollection);
$_bindParams = $accessor->getProperty('_bindParams');
$_bindParams->setAccessible(true);
$chosenIds = $productCollection->getConnection()
    ->fetchCol($idsSelect, $_bindParams->getValue($productCollection));

Then I could load the products by these random ids:

// Step 2: Load products
// Attributes and index data are joined here
$productCollection->addIdFilter($chosenIds);
$productCollection
    ->addMinimalPrice()
    ->addFinalPrice()
    ->addTaxPercents()
    ->addAttributeToSelect(Mage::getSingleton('catalog/config')->getProductAttributes())
    ->addUrlRewrite();

$productCollection->load();

Simpler alternative

An alternative that also works well on small catalogs (<10000 products) is to load all ids and select the random IDs with PHP:

$numberOfItems = 5;

$productCollection = Mage::getModel('catalog/product')->getCollection();
$productCollection
    ->addStoreFilter()
    ->setVisibility(Mage::getSingleton('catalog/product_visibility')->getVisibleInCatalogIds());
$candidateIds = $productCollection->getAllIds();
$numberOfProducts = count($candidateIds);
$chosenIds = [];
while ($numberOfItems) {
    $randomKey = mt_rand(0, $numberOfProducts - 1);
    if (!isset($chosenIds[$randomKey])) {
        chosenIds[$randomKey] = $candidateIds[$randomKey];
        --$numberOfItems;
    }
}
$productCollection->addIdFilter($chosenIds);
$productCollection
    ->addMinimalPrice()
    ->addFinalPrice()
    ->addTaxPercents()
    ->addAttributeToSelect(Mage::getSingleton('catalog/config')->getProductAttributes())
    ->addUrlRewrite();

$productCollection->load();

You can read a more in depth analysis and see some benchmarks in my blog: http://www.schmengler-se.de/en/2015/09/show-random-products-in-magento-you-are-doing-it-wrong/