[Bitrix\Main\DB\SqlQueryException] 
Mysql query error: (2006) MySQL server has gone away (400)
SELECT 
	`catalog_catalog_iblock`.`IBLOCK_ID` AS `IBLOCK_ID`,
	`catalog_catalog_iblock`.`PRODUCT_IBLOCK_ID` AS `PRODUCT_IBLOCK_ID`,
	`catalog_catalog_iblock`.`SKU_PROPERTY_ID` AS `SKU_PROPERTY_ID`,
	`catalog_catalog_iblock_iblock`.`VERSION` AS `VERSION`
FROM `b_catalog_iblock` `catalog_catalog_iblock` 
INNER JOIN `b_iblock` `catalog_catalog_iblock_iblock` ON `catalog_catalog_iblock`.`IBLOCK_ID` = `catalog_catalog_iblock_iblock`.`ID`
WHERE `catalog_catalog_iblock`.`PRODUCT_IBLOCK_ID` = 20
/home/bitrix/ext_www/pianta-shop.ru/bitrix/modules/main/lib/db/mysqliconnection.php:137
#0: Bitrix\Main\DB\MysqliConnection->queryInternal(string, array, NULL)
	/home/bitrix/ext_www/pianta-shop.ru/bitrix/modules/main/lib/db/connection.php:330
#1: Bitrix\Main\DB\Connection->query(string)
	/home/bitrix/ext_www/pianta-shop.ru/bitrix/modules/main/lib/orm/query/query.php:3193
#2: Bitrix\Main\ORM\Query\Query->query(string)
	/home/bitrix/ext_www/pianta-shop.ru/bitrix/modules/main/lib/orm/query/query.php:806
#3: Bitrix\Main\ORM\Query\Query->exec()
	/home/bitrix/ext_www/pianta-shop.ru/bitrix/modules/main/lib/orm/data/datamanager.php:467
#4: Bitrix\Main\ORM\Data\DataManager::getList(array)
	/home/bitrix/ext_www/pianta-shop.ru/bitrix/modules/catalog/general/catalog_sku.php:143
#5: CAllCatalogSku::GetInfoByProductIBlock(integer)
	/home/bitrix/ext_www/pianta-shop.ru/bitrix/modules/iblock/lib/propertyindex/facet.php:45
#6: Bitrix\Iblock\PropertyIndex\Facet->__construct(integer)
	/home/bitrix/ext_www/pianta-shop.ru/bitrix/modules/iblock/lib/propertyindex/querybuilder.php:28
#7: Bitrix\Iblock\PropertyIndex\QueryBuilder->__construct(integer)
	/home/bitrix/ext_www/pianta-shop.ru/bitrix/modules/iblock/classes/general/iblockelement.php:657
#8: CAllIBlockElement->MkFilter(array, array, array)
	/home/bitrix/ext_www/pianta-shop.ru/bitrix/modules/iblock/classes/general/iblockelement.php:3076
#9: CAllIBlockElement->PrepareGetList(array, array, array, string, array, array, NULL, NULL, array, boolean, string, array, array, array)
	/home/bitrix/ext_www/pianta-shop.ru/bitrix/modules/iblock/classes/mysql/iblockelement.php:342
#10: CIBlockElement->prepareSql(array, array, boolean, array)
	/home/bitrix/ext_www/pianta-shop.ru/bitrix/modules/iblock/classes/mysql/iblockelement.php:661
#11: CIBlockElement::GetList(array, array, boolean, boolean, array)
	/home/bitrix/ext_www/pianta-shop.ru/local/php_interface/lib/Tools.php:23
#12: Pianta\Tools::getProductUrlByOldId(integer)
	/home/bitrix/ext_www/pianta-shop.ru/catalog/index.php:7
#13: include_once(string)
	/home/bitrix/ext_www/pianta-shop.ru/bitrix/modules/main/include/urlrewrite.php:159
#14: include_once(string)
	/home/bitrix/ext_www/pianta-shop.ru/404.php:2