Magento – Catalog Search looking at descriptions = returning irrelevant search results

The key to the fact that the layer block needs to be there can be found in Mage_CatalogSearch_Block_Layer in the construct.

/**
 * Internal constructor
 */
protected function _construct()
{
    parent::_construct();
    Mage::register('current_layer', $this->getLayer(), true);
}

The second line is the key: Mage::register('current_layer', $this->getLayer(), true); without this line none of the search results will display correctly. What this does is tell the system what the current state of the search is.

This will set the current layer as type Mage_CatalogSearch_Model_Layer but if this line is not run then later on the layer gets set as type Mage_Catalog_Model_Layer. The two models have two similar but different prepareCollection functions.

Mage_CatalogSearch_Model_Layer

Has an important call to addSearchFilter

public function prepareProductCollection($collection)
{
    $collection
        ->addAttributeToSelect(Mage::getSingleton('catalog/config')->getProductAttributes())
        ->addSearchFilter(Mage::helper('catalogsearch')->getQuery()->getQueryText())
        ->setStore(Mage::app()->getStore())
        ->addMinimalPrice()
        ->addFinalPrice()
        ->addTaxPercents()
        ->addStoreFilter()
        ->addUrlRewrite();

    Mage::getSingleton('catalog/product_status')->addVisibleFilterToCollection($collection);
    Mage::getSingleton('catalog/product_visibility')->addVisibleInSearchFilterToCollection($collection);

    return $this;
}

Mage_Catalog_Model_Layer

Has no addition of addSearchFilter and does not set or filter on the store.

public function prepareProductCollection($collection)
{
    $collection
        ->addAttributeToSelect(Mage::getSingleton('catalog/config')->getProductAttributes())
        ->addMinimalPrice()
        ->addFinalPrice()
        ->addTaxPercents()
        ->addUrlRewrite($this->getCurrentCategory()->getId());

    Mage::getSingleton('catalog/product_status')->addVisibleFilterToCollection($collection);
    Mage::getSingleton('catalog/product_visibility')->addVisibleInCatalogFilterToCollection($collection);

    return $this;
}

It won't. The LIKE search requires an exact match, so unless you parse the query string and split it into separate words used to be used as the LIKE search input, it will result in no match.

LIKE search is dumb and does exactly what its input says.

You need a smarter search like LUCENE or SOLR.