Prestashop – class product.php

In folder classes look for product.php

Goto line with following code: Here Prestashop checking if combination is set and have a minimum quantity

if (!isset($combinations[$id_product]))
			$combinations[$id_product] = array();
		if (isset($combinations[$id_product][$minimum_quantity]))
			return $combinations[$id_product][$minimum_quantity];

Prestashop selects from mysql database the product attributes where quantity matching conditions

$sql = 'SELECT product_attribute_shop.id_product_attribute
				FROM '._DB_PREFIX_.'product_attribute pa
				'.Shop::addSqlAssociation('product_attribute', 'pa').'
				'.($minimum_quantity > 0 ? Product::sqlStock('pa', 'pa') : '').
				' WHERE product_attribute_shop.default_on = 1 '
				.($minimum_quantity > 0 ? ' AND IFNULL(stock.quantity, 0) >= '.(int)$minimum_quantity : '').
				' AND pa.id_product = '.(int)$id_product;
		
		$result = Db::getInstance()->getValue($sql);
		$combinations[$id_product][$minimum_quantity] = $result;
		return $result;