Question

使用MySQL 5.6我必须专门为这个子选择创建一个索引：

UPDATE site
SET site.shipping_address_id = (
    SELECT id
    FROM platform_address
    WHERE owner_id = site.numeric_id AND owner_type = 'site' AND deleted = 0
    ORDER BY modified_time
    LIMIT 1
),
    site.postal_address_id = (
    SELECT id
    FROM platform_address
    WHERE owner_id = site.numeric_id AND owner_type = 'site' AND deleted = 0
    ORDER BY modified_time
    LIMIT 1
);

我最初的想法是：

create index tmp_platform_address_for_site on platform_address (owner_id, owner_type, deleted, modified_time, id);

因为它是前3列的精确过滤器。我的理解是，查询规划器足够聪明，可以在此之后使用modified_time，然后因为id在索引中，所以根本不必打到表。

但是，该计划如下：

1   PRIMARY site    index   PRIMARY,ID_UNIQUE,numeric_id_UNIQUE,fk_site_company1,i_default_price_list_id,site_ModifiedTime  PRIMARY 108     11  Using temporary
3   DEPENDENT SUBQUERY  platform_address    ref tmp_platform_address_for_site   tmp_platform_address_for_site   8   site.numeric_id,const,const 1   Using where; Using index; Using filesort
2   DEPENDENT SUBQUERY  platform_address    ref tmp_platform_address_for_site   tmp_platform_address_for_site   8   site.numeric_id,const,const 1   Using where; Using index; Using filesort

我错过了什么吗？

此查询的正确索引是什么？

0 个答案: