1

我有以下查询构建一个记录集，该记录集在饼图中用作报告。

它不是特别经常运行，但是当它运行时需要几秒钟，我想知道是否有任何方法可以提高效率。

SELECT
  CASE
    WHEN (lastStatus IS NULL)     THEN 'Unused'
    WHEN (attempts > 3 AND callbackAfter IS NULL)   THEN 'Max Attempts Reached'
    WHEN (callbackAfter IS NOT NULL AND callbackAfter >  DATE_ADD(NOW(), INTERVAL 7 DAY)) THEN 'Call Back After 7 Days'
    WHEN (callbackAfter IS NOT NULL AND callbackAfter <= DATE_ADD(NOW(), INTERVAL 7 DAY)) THEN 'Call Back Within 7 Days'
    WHEN (archived = 0)     THEN 'Call Back Within 7 Days'
    ELSE 'Spoke To'
  END AS statusSummary,
  COUNT(leadId) AS total
FROM
  CO_Lead
WHERE
  groupId = 123
  AND
  deleted = 0
GROUP BY
  statusSummary
ORDER BY
  total DESC;

我有一个 ( groupId, deleted) 的索引，但我不确定将任何其他字段添加到索引中是否会有所帮助（如果可以，我如何决定哪个应该先行？callbackAfter因为它使用得最多？）

该表有大约 500,000 行（但从现在起每年将增加 10 倍。）

我唯一能想到的另一件事是将它分成 6 个查询（将 WHEN 子句移到 WHERE 中），但这会花费 3 倍的时间。

编辑：

这是表定义

CREATE TABLE CO_Lead (
  objectId                             int UNSIGNED       NOT NULL AUTO_INCREMENT,
  groupId                              int UNSIGNED       NOT NULL,
  numberToCall                         varchar(20)        NOT NULL,
  firstName                            varchar(100)       NOT NULL,
  lastName                             varchar(100)       NOT NULL,
  attempts                             tinyint            NOT NULL default 0,
  callbackAfter                        datetime           NULL,
  lastStatus                           varchar(30)        NULL,
  createdDate                          datetime           NOT NULL,
  archived                             bool               NOT NULL default 0,
  deleted                              bool               NOT NULL default 0,
  PRIMARY KEY (
    objectId
  )
) ENGINE = InnoDB;
ALTER TABLE CO_Lead ADD CONSTRAINT UQIX_CO_Lead UNIQUE INDEX (
  objectId
);
ALTER TABLE CO_Lead ADD INDEX (
  groupId,
  archived,
  deleted,
  callbackAfter,
  attempts
);
ALTER TABLE CO_Lead ADD INDEX (
  groupId,
  deleted,
  createdDate,
  lastStatus
);
ALTER TABLE CO_Lead ADD INDEX (
  firstName
);
ALTER TABLE CO_Lead ADD INDEX (
  lastName
);
ALTER TABLE CO_Lead ADD INDEX (
  lastStatus
);
ALTER TABLE CO_Lead ADD INDEX (
  createdDate
);
4

2 回答 2

1

尝试删除索引以查看这是否会提高性能。

在某些数据库中，索引不一定会提高性能。如果您有索引，MySQL 将始终使用它。在这种情况下，这意味着它将读取索引，然后必须从每一页读取数据。页面读取是随机的，而不是顺序的。对于必须读取所有页面的查询，这种随机读取会降低性能。

于 2012-11-29T22:10:31.527 回答
1

笔记：

  1. 如果leadId不能NULL，则更COUNT(leadId)改为COUNT(*)。它们在逻辑上是等价的，但大多数版本的 MySQL 优化器并不那么聪明地识别它。
  2. 去掉两个多余的callbackAfter IS NOT NULL条件。如果callbackAfter满足第二部分，则无论如何它都不能为空。
  3. 您可以受益于将查询分成 6 个部分并为每个部分添加适当的索引 - 但取决于条件是否CASE重叠，您可能会得到错误或正确的结果。

可能的重写（注意不同的格式并检查它是否返回相同的结果，它可能不会！）

SELECT
    cnt1 AS "Unused"
  , cnt2 AS "Max Attempts Reached"
  , cnt3 AS "Call Back After 7 Days"
  , cnt4 AS "Call Back Within 7 Days"
  , cnt5 AS "Call Back Within 7 Days"
  , cnt6 - (cnt1+cnt2+cnt3+cnt4+cnt5) AS "Spoke To"
FROM
  ( SELECT
      ( SELECT COUNT(*)  FROM CO_Lead
        WHERE groupId = 123 AND deleted = 0
          AND lastStatus IS NULL
      ) AS cnt1
    , ( SELECT COUNT(*)  FROM CO_Lead
        WHERE groupId = 123 AND deleted = 0
          AND attempts > 3 AND callbackAfter IS NULL
      ) AS cnt2
    , ( SELECT COUNT(*)  FROM CO_Lead
        WHERE groupId = 123 AND deleted = 0
          AND callbackAfter >  DATE_ADD(NOW(), INTERVAL 7 DAY)
      ) AS cnt3
    , ( SELECT COUNT(*)  FROM CO_Lead
        WHERE groupId = 123 AND deleted = 0
          AND callbackAfter <= DATE_ADD(NOW(), INTERVAL 7 DAY)
      ) AS cnt4
    , ( SELECT COUNT(*)  FROM CO_Lead
        WHERE groupId = 123 AND deleted = 0
          AND archived = 0
      ) AS cnt5
    , ( SELECT COUNT(*)  FROM CO_Lead
        WHERE groupId = 123 AND deleted = 0
      ) AS cnt6
  ) AS tmp ;

如果它确实返回正确的结果，您可以添加要用于每个子查询的索引：

对于子查询 1： (groupId, deleted, lastStatus)

对于子查询 2、3、4： (groupId, deleted, callbackAfter, attempts)

对于子查询 5： (groupId, deleted, archived)

另一种方法是保留您的查询（只注意上面的注释 1 和 2）并添加一个广泛的覆盖索引：

 (groupId, deleted, lastStatus, callbackAfter, attempts, archived)
于 2012-11-30T02:30:50.047 回答