MySQL查询视图性能低下

我在视图中使用了以下查询：

select `a`.`device_id` AS `device_id`,
       `a`.`alias` AS `alias`,
       `a`.`freq` AS `freq`,
       `a`.`gateway` AS `gateway`,
       `a`.`device_lat` AS`device_lat`,
       `a`.`device_long` AS `device_long`,
       `a`.`device_disabled` AS `device_disabled`,
       count(`b`.`msg_id`) AS `total_messages`,
       avg(`b`.`rssi`) AS `avg_rssi`,
       max(`b`.`db_timestamp`) AS `last_active`,
       (now() <= (max(`b`.`db_timestamp`) + interval 3 hour)) AS `device_status`
from `demo`.`lora_device` `a` 
left join `demo`.`lora_message` `b` on `a`.`device_id` = `b`.`eui` 
group by `a`.`device_id`

选择'a`.'device\u id`作为'device\u id`，
`a`.`alias`作为`alias`，
`a`.`freq`作为`freq`，
`a`.`gateway`作为`gateway`，
`a`.`device\u lat`作为`device\u lat`，
`a`.`device\u long`作为`device\u long`，
`a`.`device\u disabled`作为`device\u disabled`，
将（`b`.`msg\u id`）计数为`total\u messages`，
avg（`b`.`rssi`）作为`avg_rssi`，
max（`b`.`db\u timestamp`）作为`last\u active`，
（现在（）尝试添加索引

 create index ix_loramessage_rssi on lora_message(eui, rssi)
 create index ix_loramessage_db_timestamp on lora_message(eui, db_timestamp)

和使用

 count(`b`.`rssi`) AS `total_messages`,

而不是

 count(`b`.`msg_id`) AS `total_messages`,

因为它应该在您的查询中返回相同的结果
谢谢！我已经添加了索引，现在查询将在0.05秒后运行。