Prestashop sql improvements

AdminCartRulesController.php

<?php

class AdminCartRulesController extends AdminCartRulesControllerCore
{
    protected function afterAdd($currentObject)
    {
        /*
         * Omitted code...
         */

        // If the new rule has no cart rule restriction, then it must be added to the white list of the other cart rules that have restrictions
        if (!Tools::getValue('cart_rule_restriction'))
        {
            Db::getInstance()->execute('
            INSERT INTO `'._DB_PREFIX_.'cart_rule_combination` (`id_cart_rule_1`, `id_cart_rule_2`) (
                SELECT id_cart_rule, '.(int)$currentObject->id.' FROM `'._DB_PREFIX_.'cart_rule` WHERE cart_rule_restriction = 1
            )');
        }
        // And if the new cart rule has restrictions, previously unrestricted cart rules may now be restricted (a mug of coffee is strongly advised to understand this sentence)
        else
        {
            // optimization here
            $subquery = array_map(
                function($row) {
                    return $row['my_field'];
                },
                Db::getInstance()->executeS('
                    SELECT IF(id_cart_rule_1 = '.(int)$currentObject->id.', id_cart_rule_2, id_cart_rule_1) my_field
                    FROM '._DB_PREFIX_.'cart_rule_combination
                    WHERE '.(int)$currentObject->id.' = id_cart_rule_1
                    OR '.(int)$currentObject->id.' = id_cart_rule_2'
                )
            );
            $subquery = implode(',', $subquery);

            $ruleCombinations = Db::getInstance()->executeS('
            SELECT cr.id_cart_rule
            FROM '._DB_PREFIX_.'cart_rule cr
            WHERE cr.id_cart_rule != '.(int)$currentObject->id.'
            AND cr.cart_rule_restriction = 0
            AND cr.id_cart_rule NOT IN (' . $subquery . ')');
            foreach ($ruleCombinations as $incompatibleRule)
            {
                Db::getInstance()->execute('UPDATE `'._DB_PREFIX_.'cart_rule` SET cart_rule_restriction = 1 WHERE id_cart_rule = '.(int)$incompatibleRule['id_cart_rule'].' LIMIT 1');
                Db::getInstance()->execute('
                INSERT IGNORE INTO `'._DB_PREFIX_.'cart_rule_combination` (`id_cart_rule_1`, `id_cart_rule_2`) (
                    SELECT id_cart_rule, '.(int)$incompatibleRule['id_cart_rule'].' FROM `'._DB_PREFIX_.'cart_rule`
                    WHERE active = 1
                    AND id_cart_rule != '.(int)$currentObject->id.'
                    AND id_cart_rule != '.(int)$incompatibleRule['id_cart_rule'].'
                )');
            }
        }
    }
}

CartRule.php

<?php

class CartRule extends CartRuleCore
{
    protected function getCartRuleCombinations()
    {
        $subquery = array_map(
            function($row) {
                return $row['my_field'];
            },
            Db::getInstance()->executeS('
                SELECT IF(id_cart_rule_1 = '.(int)$this->id.', id_cart_rule_2, id_cart_rule_1) my_field
                FROM '._DB_PREFIX_.'cart_rule_combination
                WHERE '.(int)$this->id.' = id_cart_rule_1
                OR '.(int)$this->id.' = id_cart_rule_2'
            )
        );
        $subquery = implode(',', $subquery);

        $array = array();
        $array['selected'] = Db::getInstance()->executeS('
        SELECT cr.*, crl.*, 1 as selected
        FROM '._DB_PREFIX_.'cart_rule cr
        LEFT JOIN '._DB_PREFIX_.'cart_rule_lang crl ON (cr.id_cart_rule = crl.id_cart_rule AND crl.id_lang = '.(int)Context::getContext()->language->id.')
        WHERE cr.id_cart_rule != '.(int)$this->id.'
        AND (
            cr.cart_rule_restriction = 0
            OR cr.id_cart_rule IN (' . $subquery . ')
        )');
        $array['unselected'] = Db::getInstance()->executeS('
        SELECT cr.*, crl.*, 1 as selected
        FROM '._DB_PREFIX_.'cart_rule cr
        LEFT JOIN '._DB_PREFIX_.'cart_rule_lang crl ON (cr.id_cart_rule = crl.id_cart_rule AND crl.id_lang = '.(int)Context::getContext()->language->id.')
        WHERE cr.cart_rule_restriction = 1
        AND cr.id_cart_rule != '.(int)$this->id.'
        AND cr.id_cart_rule NOT IN (' . $subquery . ')');
        return $array;
    }
}