"Joined field with this alias is already declared" sort by custom attribute shows error

Question

I already had one custom sort by attribute which is agency_id but when i try to add new sort by attribute Location it shows me this error.

a:5:{i:0;s:48:"Joined field with this alias is already declared";i:1;s:3988:"#0 /home/test/public_html/app/code/core/Mage/Eav/Model/Entity/Collection/Abstract.php(695): Mage::exception('Mage_Eav', 'Joined field wi...')
#1 /home/test/public_html/app/code/local/Mage/Catalog/Block/Product/List.php(104): Mage_Eav_Model_Entity_Collection_Abstract->joinField('value', 'customer_entity...', 'value', 'entity_id=agenc...', Array, 'left')
#2 /home/test/public_html/app/code/local/Mage/Catalog/Block/Product/List.php(196): Mage_Catalog_Block_Product_List->_getProductCollection()
#3 /home/test/public_html/app/code/core/Mage/Core/Block/Abstract.php(918): Mage_Catalog_Block_Product_List->_beforeToHtml()
#4 /home/test/public_html/app/code/core/Mage/Core/Block/Abstract.php(637): Mage_Core_Block_Abstract->toHtml()
#5 /home/test/public_html/app/code/core/Mage/Core/Block/Abstract.php(581): Mage_Core_Block_Abstract->_getChildHtml('search_result_l...', true)
#6 /home/test/public_html/app/code/local/Mage/CatalogSearch/Block/Advanced/Result.php(103): Mage_Core_Block_Abstract->getChildHtml('search_result_l...')
#7 /home/test/public_html/app/design/frontend/default/default/template/catalogsearch/advanced/result.phtml(58): Mage_CatalogSearch_Block_Advanced_Result->getProductListHtml()

i did changes in
/app/code/local/Mage/Catalog/Block/Product/List.php

i added code in _getProductCollection() as below

$sortBy = $this->getRequest()->getParam('order');
$dir = $this->getRequest()->getParam('dir');
if($sortBy == "review"){
    /* added for rating */
    $this->_productCollection->joinField('review', 'review_entity_summary', 'rating_summary', 'entity_pk_value=entity_id', array('entity_type'=>1, 'store_id'=> Mage::app()->getStore()->getId()), 'left');
    /* added for rating */
}elseif($sortBy == "agency_id"){
    /* added for sort by agency id */
    $this->_productCollection->addAttributeToFilter('agency_id',array('neq'=>'1111'));
    $this->_productCollection->joinField('value', 'customer_entity_varchar', 'value', 'entity_id=agency_id', array('attribute_id'=>5), 'left');
    $this->_productCollection->setOrder('value', $dir);

}elseif($sortBy == "package_location"){
    /* added for sort by Location */
    $this->_productCollection->addAttributeToFilter('package_location',array('neq'=>'1111'));
    // $this->_productCollection->joinField('value', 'eav_attribute_option_value', 'value', 'option_id=package_location', array('attribute_id'=>197), 'left');
    // $this->_productCollection->setOrder('value', $dir);

}

before i added condition of package_location, agency_id was working fine.

i found this question but its different.

Thanks

Answer 1

It looks like the joinField call on the product collection is executed multiple times during one request. Likely, but not necessarily, this happens at the exact same line of code.

The field alias (first parameter) must be unique though. Make sure the relation is only joined once on initial collection allocation.

Answer 2

It's because _getProductCollection() is called multiple times across the whole PHP process. My solution is to use a static variable inside _getProductCollection():

protected function _getProductCollection()
{
  static $joined = false;

  ......

  if (!$joined) {
    // do joinField() here
    $joined = true;
  }

  ......

}

Answer 3

Try this one by changing alias name, I have changed alias to "rate"

case 'top_rated':
                    if(!strpos((string)$collection->getSelect(), 'rate') > 0) {
                        $collection->joinField(
                            'rate',                // alias
                            'review_entity_summary',      // table
                            'rating_summary',               // field
                            'entity_pk_value=entity_id',    // bind
                            array(
                                'entity_type' => 1, 
                                'store_id' => 4
                            ),                              // conditions
                            'left'                          // join type
                        );
                        $collection->getSelect()->order('rating_summary desc'); 
                    }