我需要一些幫助來優化查詢

Question

我有一個MySQL服務器。下面是有關服務器的信息：

# Variable_name, Value 
innodb_version, 5.6.19 
protocol_version, 10 
slave_type_conversions, 
version, 5.6.19-log 
version_comment, MySQL Community Server (GPL) 
version_compile_machine, x86_64 
version_compile_os, Linux 

到目前爲止，我有這個表：

CREATE TABLE `currency_rate_hist` (
    `id` bigint(20) NOT NULL AUTO_INCREMENT, 
    `currency_rate_id` bigint(20) NOT NULL, 
    `date_from` datetime NOT NULL, 
    `date_to` datetime DEFAULT NULL, 
    `rate` decimal(10,4) unsigned NOT NULL, 
    `date` datetime NOT NULL, 
    `user` varchar(100) NOT NULL, 
    `spread` decimal(12,10) NOT NULL DEFAULT '1.0000000000', 
    `commercial_rate` decimal(12,10) NOT NULL, 
    `tourism_rate` decimal(12,10) NOT NULL, 
    PRIMARY KEY (`id`), 
    KEY `idx_currency_rate_hist_fromto` (`date_from`,`date_to`), 
    KEY `fk_currency_rate_hist_cr` (`currency_rate_id`), 
    CONSTRAINT `fk_currency_rate_hist_cr` FOREIGN KEY (`currency_rate_id`) REFERENCES `currency_rate` (`id`) 
) ENGINE=InnoDB AUTO_INCREMENT=1002152 DEFAULT CHARSET=latin1 ROW_FORMAT=DYNAMIC 

Aaaaand這個SQL：

select 
    dates.min_date, first.rate as first_rate, dates.max_date, last.rate as last_rate 
from 
    (
     select 
      crh.currency_rate_id, 
      date(crh.date_from) as date, 
      min(crh.date_from) as min_date, 
      max(crh.date_from) as max_date 
     from currency_rate_hist crh 
    where 
     crh.currency_rate_id = 2 and 
     crh.date_from between now() - interval 31 day and date_format(now() - interval 1 day, '%Y-%m-%d 23:59:59') 
    group by date(crh.date_from) order by crh.date_from asc 
) as dates 
inner join (select rate, currency_rate_id, date_from from currency_rate_hist) as first on 
    first.currency_rate_id = dates.currency_rate_id and first.date_from = dates.min_date 
inner join (select rate, currency_rate_id, date_from from currency_rate_hist) as last on 
    last.currency_rate_id = dates.currency_rate_id and last.date_from = dates.max_date 
order by dates.max_date desc; 

，並在這裏被查詢的解釋：

{ 
"query_block": { 
    "select_id": 1, 
    "ordering_operation": { 
    "using_temporary_table": true, 
    "using_filesort": true, 
    "nested_loop": [ 
     { 
     "table": { 
      "table_name": "first", 
      "access_type": "ALL", 
      "rows": 739825, 
      "filtered": 100, 
      "materialized_from_subquery": { 
      "using_temporary_table": true, 
      "dependent": false, 
      "cacheable": true, 
      "query_block": { 
       "select_id": 3, 
       "table": { 
       "table_name": "currency_rate_hist", 
       "access_type": "ALL", 
       "rows": 739825, 
       "filtered": 100 
       } 
      } 
      } 
     } 
     }, 
     { 
     "table": { 
      "table_name": "last", 
      "access_type": "ref", 
      "possible_keys": [ 
      "<auto_key2>" 
      ], 
      "key": "<auto_key2>", 
      "used_key_parts": [ 
      "currency_rate_id" 
      ], 
      "key_length": "8", 
      "ref": [ 
      "first.currency_rate_id" 
      ], 
      "rows": 13, 
      "filtered": 100, 
      "materialized_from_subquery": { 
      "using_temporary_table": true, 
      "dependent": false, 
      "cacheable": true, 
      "query_block": { 
       "select_id": 4, 
       "table": { 
       "table_name": "currency_rate_hist", 
       "access_type": "ALL", 
       "rows": 739825, 
       "filtered": 100 
       } 
      } 
      } 
     } 
     }, 
     { 
     "table": { 
      "table_name": "dates", 
      "access_type": "ref", 
      "possible_keys": [ 
      "<auto_key0>" 
      ], 
      "key": "<auto_key0>", 
      "used_key_parts": [ 
      "currency_rate_id", 
      "min_date", 
      "max_date" 
      ], 
      "key_length": "20", 
      "ref": [ 
      "first.currency_rate_id", 
      "first.date_from", 
      "last.date_from" 
      ], 
      "rows": 10, 
      "filtered": 100, 
      "materialized_from_subquery": { 
      "using_temporary_table": true, 
      "dependent": false, 
      "cacheable": true, 
      "query_block": { 
       "select_id": 2, 
       "ordering_operation": { 
       "using_filesort": true, 
       "grouping_operation": { 
        "using_temporary_table": true, 
        "using_filesort": false, 
        "table": { 
        "table_name": "crh", 
        "access_type": "range", 
        "possible_keys": [ 
         "idx_currency_rate_hist_fromto", 
         "fk_currency_rate_hist_cr" 
        ], 
        "key": "idx_currency_rate_hist_fromto", 
        "used_key_parts": [ 
         "date_from" 
        ], 
        "key_length": "5", 
        "rows": 4505, 
        "filtered": 75.006, 
        "index_condition": "(`ebanxpayproduction`.`crh`.`date_from` between '2016-02-18 00:00:00' and '2016-02-18 23:59:59')", 
        "attached_condition": "(`ebanxpayproduction`.`crh`.`currency_rate_id` = 2)" 
        } 
       } 
       } 
      } 
      } 
     } 
     } 
    ] 
    } 
} 

此查詢是在我的生產服務器中不實用。我可以讓它運行10分鐘而沒有得到任何迴應。 任何想法？ 在此先感謝。

Answer 1

刪除子查詢中的子查詢和order by。這些阻礙了MySQL中索引的使用。所以，先從：

select dates.min_date, first.rate as first_rate, dates.max_date, last.rate as last_rate 
from (select crh.currency_rate_id, date(crh.date_from) as date, 
      min(crh.date_from) as min_date, max(crh.date_from) as max_date 
     from currency_rate_hist crh 
     where crh.currency_rate_id = 2 and 
      crh.date_from between now() - interval 31 day and date_format(now() - interval 1 day, '%Y-%m-%d 23:59:59') 
     group by date(crh.date_from) 
    ) dates inner join 
    currency_rate_hist first 
    on first.currency_rate_id = dates.currency_rate_id and 
     first.date_from = dates.min_date inner join 
    currency_rate_hist last 
    on last.currency_rate_id = dates.currency_rate_id and 
     last.date_from = dates.max_date 
order by dates.max_date desc; 

對於此版本，您想對currency_rate_hist(currency_rate_id, date_from)指標。

這可能會給你足夠的性能，而不需要大的改寫。