Reduce getId calls

[luigifab]

Description

This reduce number of getItemId() calls (found with Blackfire).
Same as #2957 #2677 #2699 #1571.

before (with a big cart with 51 downloadable, simple and bundle products):

after:

To check the PR, I added if ($quoteItemId != $quoteItem->getItemId()) exit('boom');.
Yes this will not change many things, but this + many others...

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All automated tests passed successfully (all builds are green)
• Add yourself to contributors list

[Flyingmana]

see question in code

[Flyingmana]

where is the ID coming from in the Collection? As far as I see its build in most of the cases without the itemId as key.

[Flyingmana]

would an alternate be to actually code getItemId() instead of relying on the __call() method?

[luigifab]

It seems that majority of collection have the "id" as key?
From lib/Varien/Data/Collection.php, there are some references for id used as key. But perhaps I'm wrong.

From the method load of a collection, there is something about the id:

magento-lts/lib/Varien/Data/Collection/Db.php

Lines 583 to 592 in fc98af9

	if (is_array($data)) {
	foreach ($data as $row) {
	$item = $this->getNewEmptyItem();
	if ($this->getIdFieldName()) {
	$item->setIdFieldName($this->getIdFieldName());
	}
	$item->addData($row);
	$item->setDataChanges(false);
	$this->addItem($item);
	}

magento-lts/lib/Varien/Data/Collection.php

Lines 359 to 365 in fc98af9

	public function addItem(Varien_Object $item)
	{
	$itemId = $this->_getItemId($item);
	if (!is_null($itemId)) {
	if (isset($this->_items[$itemId])) {
	throw new Exception('Item (' . get_class($item) . ') with the same id "' . $item->getId() . '" already exist');

[elidrissidev]

The item id is indeed the key for all collections.

[fballiano]

merged and cherrypicked to v20