<?php

class My_Module_Model_Resource_Log extends Mage_Log_Model_Resource_Log
{
    /**
     * Overrode this method to improve log cleaning speed. The query of log_customer to
     * log_customer gets exponentially slower as the amount of data increases.
     *
     * Clean customer table
     *
     * @param int $time
     *
     * @return Mage_Log_Model_Resource_Log
     */
    protected function _cleanCustomers($time)
    {
        $readAdapter    = $this->_getReadAdapter();
        $writeAdapter   = $this->_getWriteAdapter();

        $timeLimit = $this->formatDate(Mage::getModel('core/date')->gmtTimestamp() - $time);

        // retrieve last active customer log id
        $lastLogId = $readAdapter->fetchOne(
            $readAdapter->select()
                ->from($this->getTable('log/customer'), 'log_id')
                ->where('login_at < ?', $timeLimit)
                ->order('log_id DESC')
                ->limit(1)
        );
        if (!$lastLogId) {
            return $this;
        }


        /**
         * @author Kirk Madera <kirk@proofed.net>
         *
         * Replaced this query entirely. The purpose of this query is to grab the latest log id
         * for each customer. This can be done with a group by and max expression, without the
         * overhead of joins and the exponentially time increase as data increases.
         */
        //// Order by desc log_id before grouping (within-group aggregates query pattern)
        // $select = $readAdapter->select()
        //    ->from(
        //        array('log_customer_main' => $this->getTable('log/customer')),
        //        array('log_id'))
        //    ->joinLeft(
        //        array('log_customer' => $this->getTable('log/customer')),
        //        'log_customer_main.customer_id = log_customer.customer_id '
        //            . 'AND log_customer_main.log_id < log_customer.log_id',
        //        array())
        //    ->where('log_customer.customer_id IS NULL')
        //    ->where('log_customer_main.log_id < ?', $lastLogId + 1);
        $select = $readAdapter->select()
            ->from($this->getTable('log/customer'), array('log_id' => new Zend_Db_Expr('MAX(log_id)')))
            ->group('customer_id')
            ->where('log_id < ?', $lastLogId + 1);

        $needLogIds = array();

        $query = $readAdapter->query($select);
        while ($row = $query->fetch()) {
            $needLogIds[$row['log_id']] = 1;
        }
        $customerLogId = 0;
        while (true) {
            $visitorIds = array();
            $select = $readAdapter->select()
                ->from(
                    $this->getTable('log/customer'),
                    array('log_id', 'visitor_id'))
                ->where('log_id > ?', $customerLogId)
                ->where('log_id < ?', $lastLogId + 1)
                ->order('log_id')
                ->limit(100);

            $query = $readAdapter->query($select);
            $count = 0;
            while ($row = $query->fetch()) {
                $count++;
                $customerLogId = $row['log_id'];
                if (!isset($needLogIds[$row['log_id']])) {
                    $visitorIds[] = $row['visitor_id'];
                }
            }

            if (!$count) {
                break;
            }

            if ($visitorIds) {
                $condition = array('visitor_id IN (?)' => $visitorIds);

                // remove visitors from log/quote
                $writeAdapter->delete($this->getTable('log/quote_table'), $condition);

                // remove visitors from log/url
                $writeAdapter->delete($this->getTable('log/url_table'), $condition);

                // remove visitors from log/visitor_info
                $writeAdapter->delete($this->getTable('log/visitor_info'), $condition);

                // remove visitors from log/visitor
                $writeAdapter->delete($this->getTable('log/visitor'), $condition);

                // remove customers from log/customer
                $writeAdapter->delete($this->getTable('log/customer'), $condition);
            }

            if ($customerLogId == $lastLogId) {
                break;
            }
        }

        return $this;
    }
}