[英]how can this query be optimized (n+1 and dense_rank after)
如何优化此查询
WITH stats AS (SELECT a.IntegratorSalesAssociateID,
a.AgentName,
(
SELECT COUNT(*)
FROM properties AS p
WHERE a.IntegratorSalesAssociateID = p.IntegratorSalesAssociateID
AND p.TransactionType = '2'
AND MONTH(p.OrigListingDate) = MONTH(CURRENT_DATE)
AND YEAR(p.OrigListingDate) = YEAR(CURRENT_DATE)
) AS properties_this_month
FROM agents AS a)
SELECT stats.*,
DENSE_RANK() over (ORDER BY stats.properties_this_month DESC) AS 'rank'
from stats
我想也许如果我加入这两个表并以某种方式对它们进行分组,它会执行得更好,目前它运行 17.5 秒,奇怪的是,添加dense_rank 根本不会影响性能。
相关表结构
CREATE TABLE `agents`
(
`IntegratorSalesAssociateID` varchar(15) COLLATE utf8mb4_unicode_ci NOT NULL,
`AgentName` varchar(100) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
`created_at` timestamp NULL DEFAULT NULL,
`updated_at` timestamp NULL DEFAULT NULL
) ENGINE = InnoDB
DEFAULT CHARSET = utf8mb4
COLLATE = utf8mb4_unicode_ci;
CREATE TABLE `properties`
(
`id` bigint(20) UNSIGNED NOT NULL,
`IntegratorSalesAssociateID` varchar(13) COLLATE utf8mb4_unicode_ci NOT NULL,
`TransactionType` tinyint(4) NOT NULL,
`OrigListingDate` date DEFAULT NULL,
`created_at` timestamp NULL DEFAULT NULL,
`updated_at` timestamp NULL DEFAULT NULL
) ENGINE = InnoDB
DEFAULT CHARSET = utf8mb4
COLLATE = utf8mb4_unicode_ci;
你可以试试这个:
;WITH stats AS
(
SELECT
p.IntegratorSalesAssociateID
, COUNT(*) AS properties_this_month
FROM properties AS p
WHERE p.TransactionType = '2'
AND MONTH(p.OrigListingDate) = MONTH(CURRENT_DATE)
AND YEAR(p.OrigListingDate) = YEAR(CURRENT_DATE)
GROUP BY p.IntegratorSalesAssociateID
)
SELECT
a.IntegratorSalesAssociateID
, a.AgentName
, COALESCE(s.properties_this_month, 0) AS properties_this_month
FROM agents AS a
LEFT JOIN stats s ON a.IntegratorSalesAssociateID = s.IntegratorSalesAssociateID
鉴于DENSE_RANK()
不会影响性能,您需要优化:
SELECT a.IntegratorSalesAssociateID,
a.AgentName,
(SELECT COUNT(*)
FROM properties p
WHERE a.IntegratorSalesAssociateID = p.IntegratorSalesAssociateID AND
p.TransactionType = '2' AND
MONTH(p.OrigListingDate) = MONTH(CURRENT_DATE) AND
YEAR(p.OrigListingDate) = YEAR(CURRENT_DATE)
) AS properties_this_month
FROM agents a;
我会将其重写为:
SELECT a.IntegratorSalesAssociateID,
a.AgentName,
(SELECT COUNT(*)
FROM properties p
WHERE a.IntegratorSalesAssociateID = p.IntegratorSalesAssociateID AND
p.TransactionType = 2 AND
p.OrigListingDate >= CURRENT_DATE - INTERVAL (1 - DAY(CURRENT_DATE) DAY
) AS properties_this_month
FROM agents a;
这两个变化是:
TransactionType
看起来像一个数字。 假设是,我删除了单引号。 不要混合数据类型,当然,如果列是字符串。 然后使用单引号。 然后,对于此查询,您需要一个索引: properties(IntegratorSalesAssociateID, TransactionType, OrigListingDate)
。 实际上,该索引可能适用于数据的原始版本。
我真诚地怀疑使用显式聚合会提高性能。 GROUP BY
虽然非常强大——通常比相关子查询慢。 并且使用正确的索引几乎总是更慢(或至少不是更快)。
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