Question

我有一个mysql服务器。以下是有关服务器的信息：

# 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

到目前为止，我有这张表：

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这个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;

以下是查询的解释：

   {
"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)"
                  }
                }
              }
            }
          }
        }
      }
    ]
  }
}

此查询在我的生产服务器中不实用。我可以让它运行十分钟而没有得到任何回应。任何想法？提前谢谢。

Answer 1

删除子查询和子查询中的order by。这些阻碍了MySQL中索引的使用。所以，从：

开始

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;

对于此版本，您需要currency_rate_hist(currency_rate_id, date_from)上的索引。

这可以在没有重大改写的情况下为您提供足够的性能。

我需要一些帮助来优化查询

1 个答案: