Magento产品集合：每个自定义属性输出前3种产品

Question

I have created a custom attribute "quality_level" indicating three levels of quality: entrance, standard, premium.

I am now trying to create category pages, which should fully work with the layered navigation, that lists just the top 3 products for each quality level (ie up 3x3 products).

The sorting for what is regarded "top 3" is based on another custom attribute "quality_measure", which is defined between 1 (lowest) and 1000 (best).

I tried to implement it as follows:

$_productCollectionTmp = clone $this;
$_productCollection1 = $_productCollectionTmp
    ->getProductCollection()
    ->clear()
    ->addAttributeToFilter('quality_level', array('in' => array(305)))
    ->addAttributeToSort('quality_measure', 'DESC')
    ->load();

$_productCollectionTmp = clone $this;
$_productCollection2 = $_productCollectionTmp
    ->getProductCollection()
    ->clear()
    ->addAttributeToFilter('quality_level', array('in' => array(306)))
    ->addAttributeToSort('quality_measure', 'DESC')
    ->load();

...

However, this does not only feel pretty inefficient, it also results in actually no product being displayed at all as the addAttributeToFilter seems to apply to all product collections I am trying to clone.

Alternatively, I thought about a more efficient way with an additional WHERE clause, similar to this example here: http://www.xaprb.com/blog/2006/12/07/how-to-select-the-firstleastmax-row-per-group-in-sql/ (example under "Select the top N rows from each group"). However, I couldn't figure out how to operationalize this in my case.

Could I get my result with a clever statement like this?

... ->getSelect()->where("(SELECT count(*) from ...) <= 3") ...

Any ideas or suggestions?

Answer 1

You are doing it almost OK.
The problem is that once you call load on a collection the items are retrieved from the db.
After that calling reset will not make the collection load again.
So try this code:

$_productCollectionTmp = clone $this;
$_productCollection1 = $_productCollectionTmp
    ->getProductCollection()
    ->clear() //not sure if this is needed anymore
    ->addAttributeToFilter('quality_level', array('in' => array(305)))
    ->addAttributeToSort('quality_measure', 'DESC')
;

$_productCollectionTmp = clone $this;
$_productCollection2 = $_productCollectionTmp
    ->getProductCollection()
    ->clear() //not sure if this is needed anymore
    ->addAttributeToFilter('quality_level', array('in' => array(306)))
    ->addAttributeToSort('quality_measure', 'DESC')
;

Then you just need to loop through $_productCollection1 and $_productCollection2 . The load will be automatically called when doing the foreach loop.