mysql - 需要调整mysql查询

Question

我有一个查询需要一天多的时间才能完成，temp_message_split 表中有 1700128 条记录，因此请帮助调整此查询

下面提供了建表语句和解释计划。

UPDATE TEMP_MESSAGE_SPLIT t1 , TEMP_MESSAGE_SPLIT t2
    SET t1.STATUS = 'D'
    WHERE
    (t1.temp_message_split_key < t2.temp_message_split_key AND t1.DH_MEMBER_ID = t2.DH_MEMBER_ID)
    AND  nullif(t1.dh_member_id,'') IS NOT NULL;

这里是创建表DDL

CREATE TABLE
temp_message_split
(
    FIRST_NAME VARCHAR(20),
    LAST_NAME VARCHAR(30),
    DOB VARCHAR(10),
    EMPLOYEE_ID VARCHAR(20),
    CES_CUST_NUM VARCHAR(7),
    MED_POLICY_NUM VARCHAR(20),
    EMAIL_ADDR VARCHAR(50),
    DH_MEMBER_ID VARCHAR(9),
    ALT_ID VARCHAR(20),
    DRSN VARCHAR(2),
    SSN VARCHAR(9),
    EPIPHANY_MEMBER_ID VARCHAR(18),
    PORTAL_ADDRESS VARCHAR(30),
    STATEMENT_VENDOR VARCHAR(20),
    CONTENT_KEY VARCHAR(18),
    EPIPHANY_COMMUNICATION_ID VARCHAR(200),
    PRIORITY VARCHAR(4),
    DAYS_UNTIL_EXPIRED VARCHAR(4),
    CONTENT_DTL_KEY VARCHAR(18),
    STATUS VARCHAR(1),
    ACTIVATION_MEMBER_KEY bigint,
    MESSAGE_BOARD_KEY bigint,
    PORTAL_STATEMENT_LOC_KEY bigint,
    temp_message_split_KEY bigint NOT NULL AUTO_INCREMENT,
    PRIMARY KEY (temp_message_split_KEY),
    INDEX EPIPHANY_COMMUNICATION_ID_IDX (EPIPHANY_COMMUNICATION_ID),
    INDEX TEMP_MESSAGE_SPLIT_IDX2 (ALT_ID),
    INDEX TEMP_MESSAGE_SPLIT_IDX3 (DRSN),
    INDEX TEMP_MESSAGE_SPLIT_IDX4 (ALT_ID, DRSN),
    INDEX TEMP_MESSAGE_SPLIT_IDX1 (DH_MEMBER_ID)
)
ENGINE=InnoDB DEFAULT CHARSET=utf8;

这是它的解释计划:

+----+-------------+-------+------------+-------+---------------------------------+-------------------------+---------+------+---------+----------+------------------------------------------------+
| id | select_type | table | partitions | type  | possible_keys                   | key                     | key_len | ref  | rows    | filtered | Extra                                          |
+----+-------------+-------+------------+-------+---------------------------------+-------------------------+---------+------+---------+----------+------------------------------------------------+
|  1 | SIMPLE      | t2    | NULL       | index | PRIMARY,TEMP_MESSAGE_SPLIT_IDX1 | TEMP_MESSAGE_SPLIT_IDX1 | 30      | NULL | 1619639 |   100.00 | Using index                                    |
|  1 | UPDATE      | t1    | NULL       | ALL   | PRIMARY,TEMP_MESSAGE_SPLIT_IDX1 | NULL                    | NULL    | NULL | 1619639 |    33.33 | Range checked for each record (index map: 0x5) |
+----+-------------+-------+------------+-------+---------------------------------+-------------------------+---------+------+---------+----------+------------------------------------------------+
2 rows in set (0.00 sec)

此查询需要一天多的时间来处理 temp_message_split 表中的 1700128，我们需要对其进行调整，使其花费尽可能多的时间。时间尽可能。

Answer 1

我最好的猜测是您想将状态设置为 D对于除最高值 temp_message_split_key 之外的所有值对于每个 DH_MEMBER_ID 。

最好的解决方案是NOT EXISTS ，但MySQL不支持NOT EXISTS在 UPDATE 的同一张 table 上查询。

因此，另一种方法使用 GROUP BY :

UPDATE TEMP_MESSAGE_SPLIT t1 JOIN
       (SELECT t2.DH_MEMBER_ID, MAX(t2.temp_message_split_key) as max_temp_message_split_key
        FROM TEMP_MESSAGE_SPLIT t2
        GROUP BY t2.DH_MEMBER_ID
       ) t2
       ON t1.DH_MEMBER_ID = t2.DH_MEMBER_ID AND
          t1.temp_message_split_key < t2.max_temp_message_split_key
    SET t1.STATUS = 'D';

(dh_member_id, temp_message_split_key) 上的索引可能有助于提高性能。

这仍然需要很长时间，因为您(大概)正在更新很多行。如果可能的话，那么用您想要的值创建一个新表可能会更简单。这会快得多(由于日志记录和锁定)。

NULLIF()可能什么也没做，但它对查询性能的影响很小。最好写成 t1.dh_member_id <> '' .