database - Magento Varien_Data_Collections: when is SQL query executed -

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i`d know how magento internally processes database calls on varien_data_collections. example: 1 of models returns data collection block. additional clauses added via layout xml blocks , afterwards appended returned data collection te model.

does mean database calls made twice? 1 on initial $model->getcollection() method , 1 on $collection->addfieldtofilter('x',array('eq'=>'y')) in block.

or magento make sql call on iteraror?

see situation below:

model class: 

<?php  class x_y_model_a extends mage_core_model_abstract{     ...      public function getrelateditems(){         return $this->getcollection()             ->addfieldtofilter('id',array('eq'=>$this->getid()));     } }  ?>

block class:

<?php  class x_y_block_a extends mage_core_block_template{      private $limit = 5;      public function setdblimit($limit){         $this->limit = (int)$limit;         return $this;     }      public function getdblimit(){         return $this->limit;     }      public function getrelateditems(){         $_collection = mage::getmodel('xy/a')->getrelateditems();         $_collection->setpagesize($this->getdblimit());         return $_collection;     }  }  ?>

layout xml file

<layout>     ...     <reference name="content">         <block type="xy/a" name="xy" as="xy" template="xy/related.phtml">             <action method="setdblimit"><limit>2<limit></action>         </block>     </reference> </layout>

view .phtml

<?php      // xy/related.phtml     $_relateditems = $this->getrelateditems();      if($_relateditems->getsize()>0){         foreach($_relateditems $_relateditem){             // html output         }     } ?>

magento uses lazy-loading , performs query when needs data resultset. long don't use result, can keep adding conditionals or filters without executing query.


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