如何使该MySQL查询（带有子查询）更快？

时间：2019-01-15 15:34:16

标签： mysql sql performance woocommerce entity-attribute-value

我有以下查询可获取订单数据，工作正常，但需要13.63秒：

SELECT
( SELECT meta_value FROM `myprefix_postmeta` as postmeta WHERE postmeta.meta_key = '_sku' AND postmeta.post_id = woocommerce_order_itemmeta3.meta_value ) AS sku,
woocommerce_order_items.order_item_name AS title,
SUM( woocommerce_order_itemmeta.meta_value ) AS quantity,
SUM( woocommerce_order_itemmeta2.meta_value ) AS total
FROM `myprefix_woocommerce_order_items` AS woocommerce_order_items
LEFT JOIN `myprefix_posts` AS posts ON posts.ID = woocommerce_order_items.order_id
LEFT JOIN `myprefix_woocommerce_order_itemmeta` AS woocommerce_order_itemmeta ON woocommerce_order_itemmeta.order_item_id = woocommerce_order_items.order_item_id
LEFT JOIN `myprefix_woocommerce_order_itemmeta` AS woocommerce_order_itemmeta2 ON woocommerce_order_itemmeta2.order_item_id =   woocommerce_order_items.order_item_id
LEFT JOIN `myprefix_woocommerce_order_itemmeta` AS woocommerce_order_itemmeta3 ON woocommerce_order_itemmeta3.order_item_id =   woocommerce_order_items.order_item_id
WHERE posts.post_type = 'shop_order'
AND posts.post_status IN( 'wc-completed', 'wc-processing', 'wc-on-hold' )
AND woocommerce_order_itemmeta.meta_key = '_qty'
AND woocommerce_order_itemmeta2.meta_key = '_line_total' 
AND woocommerce_order_itemmeta3.meta_key = '_product_id'
GROUP BY woocommerce_order_itemmeta3.meta_value
ORDER BY total DESC

我想优化此查询以使其运行更快。

也许只是需要很长时间才能返回。但是，无论如何，我都试图删除上面的子查询，结果如下：

SELECT
postmeta.meta_value AS sku,
woocommerce_order_items.order_item_name AS title,
SUM( woocommerce_order_itemmeta.meta_value ) AS quantity,
SUM( woocommerce_order_itemmeta2.meta_value ) AS total
FROM `myprefix_woocommerce_order_items` AS woocommerce_order_items
LEFT JOIN `myprefix_posts` AS posts ON posts.ID = woocommerce_order_items.order_id
LEFT JOIN `myprefix_postmeta` AS postmeta ON posts.ID = woocommerce_order_items.order_id
LEFT JOIN `myprefix_woocommerce_order_itemmeta` AS woocommerce_order_itemmeta ON woocommerce_order_itemmeta.order_item_id = woocommerce_order_items.order_item_id
LEFT JOIN `myprefix_woocommerce_order_itemmeta` AS woocommerce_order_itemmeta2 ON woocommerce_order_itemmeta2.order_item_id =   woocommerce_order_items.order_item_id
LEFT JOIN `myprefix_woocommerce_order_itemmeta` AS woocommerce_order_itemmeta3 ON woocommerce_order_itemmeta3.order_item_id =   woocommerce_order_items.order_item_id
WHERE posts.post_type = 'shop_order'
AND posts.post_status IN( 'wc-completed', 'wc-processing', 'wc-on-hold' )
AND postmeta.meta_key = '_sku'
AND postmeta.post_id = woocommerce_order_itemmeta3.meta_value
AND woocommerce_order_itemmeta.meta_key = '_qty'
AND woocommerce_order_itemmeta2.meta_key = '_line_total' 
AND woocommerce_order_itemmeta3.meta_key = '_product_id'
GROUP BY woocommerce_order_itemmeta3.meta_value
ORDER BY total DESC

这快几毫秒，但是有什么方法可以进一步优化吗？

非常感谢您可能需要了解这些表背后的数据，它们是标准的WordPress database tables和WooCommerce Database Schema，我无法真正共享这些表背后的数据。

上面的第二个示例存在一个附带问题，即如果SKU为NULL，则不包含该行，而最上面的一个包含该行，因此目前仍然是首选查询。

更新＃1

基于答案：https://stackoverflow.com/a/54202562/8369600

我最初从答案的第1部分更新了我的代码格式，并且效果很好。

然后我在步骤2中使用了代码，并对格式进行了一些细微更改，以便在phpMyAdmin中为我工作，这些更改是：

SELECT
    (SELECT meta_value
        FROM `myprefix_postmeta` as postmeta 
        WHERE 
            postmeta.meta_key = '_sku' 
            AND postmeta.post_id = ( -- Substitute meta_value with CASE-expressions 
                    CASE
                        WHEN IM.meta_key = '_product_id' THEN IM.meta_value
                        ELSE NULL
                    END 
                ) -- IM3.meta_value               
            ) AS sku,
            -- think above is okay ^^^^
    I.order_item_name AS title,
    SUM(
        CASE -- Substitute meta_value with CASE-expressions 
            WHEN IM.meta_key = '_qty' THEN IM.meta_value
            ELSE 0 
        END 
    ) AS quantity,
    -- IM2.meta_value ) AS total
SUM( -- Substitute meta_value with CASE-expressions 
    CASE
            WHEN IM.meta_key = '_line_total' THEN IM.meta_value
            ELSE 0
    END 
) AS total       

FROM 
    `myprefix_woocommerce_order_items` AS I
    LEFT JOIN `myprefix_posts` AS posts 
    ON posts.ID = I.order_id
    LEFT JOIN `myprefix_woocommerce_order_itemmeta` AS IM -- Make readable aliases
        ON IM.order_item_id = I.order_item_id 
            AND IM.meta_key IN('_qty', '_line_total', '_product_id')
    --         AND IM.meta_key = '_qty'   -- Move predicates from WHERE
    -- LEFT JOIN `myprefix_woocommerce_order_itemmeta` AS IM2 
    --     ON IM2.order_item_id =   I.order_item_id
    --         AND IM2.meta_key = '_line_total' -- Move predicates from WHERE
    -- LEFT JOIN `myprefix_woocommerce_order_itemmeta` AS IM3 
    --     ON IM3.order_item_id =   I.order_item_id
    --         AND IM3.meta_key = '_product_id' -- Move predicates from WHERE
WHERE 
    posts.post_type = 'shop_order'
    AND posts.post_status IN
    ( 'wc-completed', 'wc-processing', 'wc-on-hold' )
GROUP BY 
    (
        CASE
            WHEN IM.meta_key = '_product_id' THEN IM.meta_value
            ELSE NULL
        END 
    ) -- IM3.meta_value    
ORDER BY 
    total DESC

但是这返回：

enter image description here

在所有行都填充有数据之前，请怀疑这些案例是否与原始案例不符。

请注意，我还按照前面的注释之一的要求，添加了指向WooCommerce数据库文档的链接。

3 个答案:

答案 0 :(得分：2)

步骤1：创建易于理解的别名并将meta_key谓词移至JOIN s

为了清楚起见，我采取了自由格式化您的查询的方式。

我重命名了别名，并将meta_key谓词从WHERE移到JOIN s：

SELECT
    (SELECT meta_value
        FROM `myprefix_postmeta` as postmeta 
        WHERE 
            postmeta.meta_key = '_sku' 
            AND postmeta.post_id = IM3.meta_value ) AS sku,
    I.order_item_name AS title,
    SUM (IM.meta_value ) AS quantity,
    SUM (IM2.meta_value ) AS total
FROM 
    `myprefix_woocommerce_order_items` AS I
    LEFT JOIN `myprefix_posts` AS posts 
    ON posts.ID = I.order_id
    LEFT JOIN `myprefix_woocommerce_order_itemmeta` AS IM -- Make readable aliases
        ON IM.order_item_id = I.order_item_id 
            AND IM.meta_key = '_qty'   -- Move predicates from WHERE
    LEFT JOIN `myprefix_woocommerce_order_itemmeta` AS IM2 
        ON IM2.order_item_id =   I.order_item_id
            AND IM2.meta_key = '_line_total' -- Move predicates from WHERE
    LEFT JOIN `myprefix_woocommerce_order_itemmeta` AS IM3 
        ON IM3.order_item_id =   I.order_item_id
            AND IM3.meta_key = '_product_id' -- Move predicates from WHERE
WHERE 
    posts.post_type = 'shop_order'
    AND posts.post_status IN
    ( 'wc-completed', 'wc-processing', 'wc-on-hold' )
GROUP BY 
    IM3.meta_value
ORDER BY 
    total DESC

现在，我们有了绝对等效的查询。

让我们看看我们可以做些什么。

  1. 具有相同谓词LEFT JOIN的3个myprefix_woocommerce_order_itemmeta至IM.order_item_id = I.order_item_id看起来不必要的重复
  2. 但是我们在meta_key上有不同的谓词

步骤2：仅用1个替换3个JOIN，用CASE表达式替换JOINed字段

所以我们可以：

a。用一个JOIN替换3个JOIN

b。用CASE表达式替换IM / IM2 / IM3字段

SELECT
    (SELECT meta_value
        FROM `myprefix_postmeta` as postmeta 
        WHERE 
            postmeta.meta_key = '_sku' 
            AND postmeta.post_id = ( -- Substitute meta_value with CASE-expressions 
                    CASE
                        WHEN IM.meta_key = '_product_id' THEN IM.meta_value
                        ELSE NULL
                    END 
                ) -- IM3.meta_value               
            ) AS sku,
    I.order_item_name AS title,
    SUM (
        CASE -- Substitute meta_value with CASE-expressions 
            WHEN IM.meta_key = '_qty' THEN IM.meta_value
            ELSE 0 
        END 
    ) AS quantity
    -- IM2.meta_value ) AS total
SUM ( -- Substitute meta_value with CASE-expressions 
    CASE
            WHEN IM.meta_key = '_line_total' THEN IM.meta_value
            ELSE 0
    END 
) AS total       

FROM 
    `myprefix_woocommerce_order_items` AS I
    LEFT JOIN `myprefix_posts` AS posts 
    ON posts.ID = I.order_id
    LEFT JOIN `myprefix_woocommerce_order_itemmeta` AS IM -- Make readable aliases
        ON IM.order_item_id = I.order_item_id 
            AND IM.meta_key IN ('_qty', '_line_total', '_product_id')
    --         AND IM.meta_key = '_qty'   -- Move predicates from WHERE
    -- LEFT JOIN `myprefix_woocommerce_order_itemmeta` AS IM2 
    --     ON IM2.order_item_id =   I.order_item_id
    --         AND IM2.meta_key = '_line_total' -- Move predicates from WHERE
    -- LEFT JOIN `myprefix_woocommerce_order_itemmeta` AS IM3 
    --     ON IM3.order_item_id =   I.order_item_id
    --         AND IM3.meta_key = '_product_id' -- Move predicates from WHERE
WHERE 
    posts.post_type = 'shop_order'
    AND posts.post_status IN
    ( 'wc-completed', 'wc-processing', 'wc-on-hold' )
GROUP BY 
    (
        CASE
            WHEN IM.meta_key = '_product_id' THEN IM.meta_value
            ELSE NULL
        END 
    ) -- IM3.meta_value    
ORDER BY 
    total DESC

PS

写没有数据的SQL不太舒服。

对于每个版本的mysql，此查询可能都不正确。

因此，请尝试理解原理，而不仅仅是复制粘贴我的代码。

将结果或问题通知我们。

答案 1 :(得分：1)

如果woocommerce是WordPress的分支，则他们可能在索引myprefix_woocommerce_order_itemmeta方面做得很差。调整here中的技巧以提高性能。

我同意其他人-EAV模式模式很糟糕。我上面的索引建议对 some 有帮助。

例如，“ order”始终具有数量，product_id，line_total；那么，为什么不将它们作为真实的列而不是将它们隐藏在另一个表中，就好像它们是稀有属性一样呢？对于只有一些商品具有“衣着尺寸”或“ F-stop”或“传输类型”的购物网站，EAV有点必要。 （在这种情况下，JSON 可能比EAV更好。）

架构审核

好，woocommerce比WP（reference）差：

CREATE TABLE {$wpdb->prefix}woocommerce_order_itemmeta (
  meta_id BIGINT UNSIGNED NOT NULL auto_increment,
  order_item_id BIGINT UNSIGNED NOT NULL,
  meta_key varchar(255) default NULL,
  meta_value longtext NULL,
  PRIMARY KEY  (meta_id),
  KEY order_item_id (order_item_id),
  KEY meta_key (meta_key(32))
) $collate;

前缀索引（meta_key(32)）很少有用，并且通常适得其反。尽管如此，可能我所有的建议（请参见上面的链接）都适用，并且名称进行了适当的更改。

答案 2 :(得分：0)

要做的第一件事是检查在LEFT JOIN和过滤位置的所有列上是否有正确的索引。通常，缺少索引是导致查询缓慢的原因。

如果您想走得更远，我将重建索引。也许一些碎片也使事情变慢了。

尽管不是必需的，您也可以尝试将已完成wc，进行wc处理的迁移键制作到自己的表中，并通过INT进行联接。

您还可以尝试规范化SUM甚至为它们创建一个计算列。

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