mysql - 使用自连接和子查询优化 UPDATE SQL 查询

Question

我的 SQL 查询更新数据库中的所有股票，但它的工作效率不高，有时我会收到 504 超时错误。该代码工作正常。我怎样才能让它更好地工作。

P.S:请忽略缺少准备好的语句，稍后我会添加它们。

关于表格的一些信息(Wordpress Woocommerce 插件默认表格):

wp_posts:此表包含帖子。 (帖子可以是产品或产品变体。例如产品是蝴蝶 T 恤，产品变体是蝴蝶 T 恤红色大号)。

wp_postmeta:此表包含有关帖子的元信息。例如，产品变体是否有库存，或者它是什么颜色，或者它是什么尺寸。

  //This array gives, which products are there, and their respective categories.
  $allProducts = array("Fermuarlı Kapşonlu Sweatshirt" => "'2653','2659'","Kapşonlu Sweatshirt" => "'2646','2651'","Sweatshirt" => "'2644','2650'","Kadın Tişört" => "'2654','2656'","Atlet" => "'2655','2657'","Tişört" => "'2643','2304'");

  //Below arrays gives information about, which product variations are out of stock.
  $tisort_OutOfStock =array();
  $atlet_OutOfStock =array("all_colors"=>"'3xl','4xl','5xl'");
  $kadin_tisort_OutOfStock =array("all_colors"=>"'xxl','3xl','4xl','5xl'");
  $sweatshirt_OutOfStock =array("beyaz"=>"'xxl','3xl','4xl','5xl'","kirmizi"=>"'xxl','3xl','4xl','5xl'","bordo"=>"'5xl'","antrasit"=>"'5xl'");
  $kapsonlu_sweatshirt_OutOfStock =array("gri-kircilli"=>"'5xl'");
  $fermuarli_kapsonlu_sweatshirt_OutOfStock =array("gri-kircilli"=>"'5xl'","siyah"=>"'5xl'");

  //Reset stocks before updating.
  $resetStocks = "UPDATE wp_postmeta set meta_value = 'instock' where meta_key = '_stock_status'";
  $wpdb->query($resetStocks);
  echo "Stoklar are reseted<br>";

  //Foreach product, foreach color, update if product doesn't have stock.
  foreach( $allProducts as $key => $urun ){

    switch ($key) {
    case "Kadın Tişört": $tempArray = $kadin_tisort_OutOfStock; break;
    case "Fermuarlı Kapşonlu Sweatshirt": $tempArray = $fermuarli_kapsonlu_sweatshirt_OutOfStock; break;
    case "Kapşonlu Sweatshirt": $tempArray = $kapsonlu_sweatshirt_OutOfStock; break;
    case "Sweatshirt": $tempArray = $sweatshirt_OutOfStock; break;
    case "Atlet": $tempArray = $atlet_OutOfStock; break;
    case "Tişört": $tempArray = $tisort_OutOfStock; break;
    }

    foreach( $tempArray as $color => $size ){

      $query = "UPDATE wp_postmeta set meta_value = 'outofstock' where meta_key = '_stock_status' and post_id in
      (
      select post_id from (select * from wp_postmeta) AS X where meta_key = 'attribute_pa_beden' and meta_value in (".$size.")
      and post_id in (select post_id from (select * from wp_postmeta) AS Y where meta_key = 'attribute_pa_renk' and ((meta_value = '".$color."') OR ('".$color."' = 'all_colors')))
      and post_id in (select id from wp_posts where post_type = 'product_variation' and post_parent in (select object_id FROM wp_term_relationships where term_taxonomy_id in (".$urun.")))
      )";

      global $wpdb;
      $updatedRowCount = $wpdb->query($query);
    }
  }

Answer 1

从键 SELECT 开始:

        SELECT  post_id
            from  
            (
                SELECT  *
                    from  wp_postmeta
            ) AS X
            where  meta_key = 'attribute_pa_beden'
              and  meta_value in (".$size.")
              and  post_id in (
                SELECT  post_id
                    from  
                    (
                        SELECT  *
                            from  wp_postmeta
                    ) AS Y
                    where  meta_key = 'attribute_pa_renk'
                      and  ((meta_value = '".$color."')
                              OR  ('".$color."' = 'all_colors'))
                          )
              and  post_id in (
                SELECT  id
                    from  wp_posts
                    where  post_type = 'product_variation'
                      and  post_parent in (
                        SELECT  object_id
                            FROM  wp_term_relationships
                            where  term_taxonomy_id in (".$urun."))) 
                      )";

是的，我知道您需要从 UPDATE wp_postmeta 中“隐藏”wp_postmeta，但我们可以重新安排内容以提高效率。请注意，您如何在两种情况下获取整个 wp_postmeta before 过滤？这使得无法使用任何索引，因此速度很慢。

SELECT m1.post_id
    FROM wp_postmeta AS m1
    JOIN wp_postmeta AS m2  USING(post_id)
    JOIN wp_posts    AS p2  USING(post_id)
    JOIN wp_term_relationships AS tr  ON p2.post_parent = tr.object_id
    WHERE m1.meta_key = 'attribute_pa_beden' AND   m1.meta_value in ("$size")
      AND m2.meta_key = 'attribute_pa_renk'  AND ( m1.meta_value = '$color'
                                                   OR '$color' = 'all_colors' )
      AND p2.post_type = 'product_variation'
      AND tr.term_taxonomy_id IN ($urun)

忘记 UPDATE 直到你得到这个 SELECT 调试。 (我可能犯了一些错误，但它看起来不是更简单吗？它会运行得更快，尤其是使用我推荐的索引。)

带颜色的 OR 可能会被优化掉，所以我不担心。

我无法预测优化器将从 4 个表中的哪一个开始，因此需要这些索引来为其提供选择:

tr:  (term_taxonomy_id, object_id)  -- in this order
posts:  (post_type, post_id)        -- in this order
postmeta:  (meta_key, meta_value)   -- see note below

在优化器选择从哪个表开始后，它会依次转到其他每个表；订单对我们来说无关紧要。这些额外的索引可能会有用:

posts:   (post_parent, post_id)        -- in this order
postmeta:  (post_id, meta_key, meta_value)   -- see note below

如果 meta_value 是 LONGTEXT，那么它不能在索引中，所以把它去掉。 (不，不要为“前缀”索引而烦恼。)

如果您使用的是 MySQL 5.5 或 5.6，meta_key 太长，无法作为索引；看我的 link多种解决方法。

EAV 架构很糟糕，您正在找出原因。

回到 UPDATE 的拼凑，添加包装器:

UPDATE wp_postmeta AS m
    JOIN  ( SELECT post_id
              FROM ( the above query )
          ) AS kludge  USING (post_id)
    SET   m.meta_value = 'outofstock'
    WHERE m.meta_key = '_stock_status'