Are unconverted quote records ever removed in Magento?

Question

tl;dr: There appears to be no other out-of-box mechanism for deleting quote records which were never converted to orders.

The Mage_Sales module has a scheduled job to clean expired quotes, but this only deletes sales_flat_quote records which are marked as inactive (i.e. is_active = 0). To my knowledge, quotes are only marked as inactive when a quote converts to an order. If this is the case, then the quote table will only grow larger and larger.

Ref Mage_Sales_Model_Observer::cleanExpiredQuotes()

class Mage_Sales_Model_Observer
{
    //...

    public function cleanExpiredQuotes($schedule)
    {
        Mage::dispatchEvent('clear_expired_quotes_before', array('sales_observer' => $this));

        $lifetimes = Mage::getConfig()->getStoresConfigByPath('checkout/cart/delete_quote_after');
        foreach ($lifetimes as $storeId=>$lifetime) {
            $lifetime *= 86400;

            /** @var $quotes Mage_Sales_Model_Mysql4_Quote_Collection */
            $quotes = Mage::getModel('sales/quote')->getCollection();

            $quotes->addFieldToFilter('store_id', $storeId);
            $quotes->addFieldToFilter('updated_at', array('to'=>date("Y-m-d", time()-$lifetime)));
            $quotes->addFieldToFilter('is_active', 0);

            foreach ($this->getExpireQuotesAdditionalFilterFields() as $field => $condition) {
                $quotes->addFieldToFilter($field, $condition);
            }

            $quotes->walk('delete');
        }
        return $this;
    }

    //...
}

Answer 1

Overwrite the observer with your own cleanup routine. We keep specific quotes for specific periods of time, hence 4 tiers of deletion. Guest carts get remail and are recoverable, empty registered customer quotes expire beside completed quotes and registered carts with contents get saved for a long period per observed customer behavior.

<?php
/**
 * Magento
 *
 * NOTICE OF LICENSE
 *
 * This source file is subject to the Open Software License (OSL 3.0)
 * that is bundled with this package in the file LICENSE.txt.
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 *
 * @category    Mage
 * @package     Mage_Sales
 * @copyright   Copyright (c) 2010 Magento Inc. (http://www.magentocommerce.com)
 * @license     http://opensource.org/licenses/osl-3.0.php  Open Software License (OSL 3.0)
 */


/**
 * Sales observer
 *
 * @category   Chief
 * @package    Chief_Sales
 * @author     Magento Core Team <[email protected]>
 */

/* Valid for 1.4.2.0, 1.5.1.0 */

class Chief_Sales_Model_Observer extends Mage_Sales_Model_Observer
{
    /**
     * Clean expired quotes (cron process)
     *
     * @param Mage_Cron_Model_Schedule $schedule
     * @return Mage_Sales_Model_Observer
     */
    public function cleanExpiredQuotes($schedule)
    {
        $lifetimes = Mage::getConfig()->getStoresConfigByPath('checkout/cart/delete_quote_after');

        /* Quotes converted to orders */
        foreach ($lifetimes as $storeId=>$lifetime) {
            $lifetime *= 86400;

            $quotes = Mage::getModel('sales/quote')->getCollection();
            /* @var $quotes Mage_Sales_Model_Mysql4_Quote_Collection */

            $quotes->addFieldToFilter('store_id', $storeId);
            $quotes->addFieldToFilter('updated_at', array('to'=>date("Y-m-d", time()-$lifetime)));
            $quotes->addFieldToFilter('is_active', 0);            // Filled Quotes
            $quotes->walk('delete');
        }


        /* Quotes abandoned by Guest Carts */
        foreach ($lifetimes as $storeId=>$lifetime) {
            $lifetime *= 86400;

            // triple lifetime for abandoned cart remail
            $lifetime *= 3;

            $quotes = Mage::getModel('sales/quote')->getCollection();
            /* @var $quotes Mage_Sales_Model_Mysql4_Quote_Collection */

            $quotes->addFieldToFilter('store_id', $storeId);
            $quotes->addFieldToFilter('updated_at', array('to'=>date("Y-m-d", time()-$lifetime)));
            $quotes->addFieldToFilter('is_active', 1);            // Active Quotes
            $quotes->addFieldToFilter('customer_group_id', 0);    // Which are Group NLI (Guest)
            $quotes->walk('delete');
        }


        /* Quotes abandoned by Registered carts no contents */
        foreach ($lifetimes as $storeId=>$lifetime) {
            $lifetime *= 86400;

            $quotes = Mage::getModel('sales/quote')->getCollection();
            /* @var $quotes Mage_Sales_Model_Mysql4_Quote_Collection */

            $quotes->addFieldToFilter('store_id', $storeId);
            $quotes->addFieldToFilter('updated_at', array('to'=>date("Y-m-d", time()-$lifetime)));
            $quotes->addFieldToFilter('is_active', 1);                      // Active Quotes
            $quotes->addFieldToFilter('customer_group_id', array('gt'=>0)); // For all other groups
            $quotes->addFieldToFilter('items_qty', 0);                      // For empty carts
            $quotes->walk('delete');
        }


        /* Quotes abandoned by Registered carts */
        foreach ($lifetimes as $storeId=>$lifetime) {
            $lifetime *= 86400;

            // Registered cart lifetime for abandoned cart remail 7*25 = 175 days
            $lifetime *= 25;

            $quotes = Mage::getModel('sales/quote')->getCollection();
            /* @var $quotes Mage_Sales_Model_Mysql4_Quote_Collection */

            $quotes->addFieldToFilter('store_id', $storeId);
            $quotes->addFieldToFilter('updated_at', array('to'=>date("Y-m-d", time()-$lifetime)));
            $quotes->addFieldToFilter('is_active', 1);                      // Active Quotes
            $quotes->addFieldToFilter('customer_group_id', array('gt'=>0)); // For all other groups
            $quotes->addFieldToFilter('items_qty', array('gt'=>0));         // For expired carts
            $quotes->walk('delete');
        }
        return $this;
    }
}