Mysql GROUP BY使用Filesort-查詢優化

Question

我有一張這樣的桌子：

CREATE TABLE `purchase` (
  `fact_purchase_id` binary(16) NOT NULL,
  `purchase_id` int(10) unsigned NOT NULL,
  `purchase_id_primary` int(10) unsigned DEFAULT NULL,
  `person_id` int(10) unsigned NOT NULL,
  `person_id_owner` int(10) unsigned NOT NULL,
  `service_id` int(10) unsigned NOT NULL,
  `fact_count` int(10) unsigned NOT NULL DEFAULT '0',
  `fact_type` tinyint(3) unsigned NOT NULL,
  `date_fact` date NOT NULL,
  `purchase_name` varchar(255) DEFAULT NULL,
  `activation_price` decimal(7,2) unsigned NOT NULL DEFAULT '0.00',
  `activation_price_total` decimal(7,2) unsigned NOT NULL DEFAULT '0.00',
  `renew_price` decimal(7,2) unsigned DEFAULT '0.00',
  `renew_price_total` decimal(7,2) unsigned NOT NULL DEFAULT '0.00',
  `activation_cost` decimal(7,2) unsigned DEFAULT '0.00',
  `activation_cost_total` decimal(7,2) unsigned NOT NULL DEFAULT '0.00',
  `renew_cost` decimal(7,2) unsigned DEFAULT '0.00',
  `renew_cost_total` decimal(7,2) unsigned NOT NULL DEFAULT '0.00',
  `date_created` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (`fact_purchase_id`),
  KEY `purchase_id_idx` (`purchase_id`),
  KEY `person_id_idx` (`person_id`),
  KEY `person_id_owner_idx` (`person_id_owner`),
  KEY `service_id_idx` (`service_id`),
  KEY `fact_type_idx` (`fact_type`),
  KEY `renew_price_idx` (`renew_price`),
  KEY `renew_cost_idx` (`renew_cost`),
  KEY `renew_price_year_idx` (`renew_price_year`),
  KEY `renew_cost_year_idx` (`renew_cost_year`),
  KEY `date_created_idx` (`date_created`),
  KEY `purchase_id_primary_idx` (`purchase_id_primary`),
  KEY `fact_count` (`fact_count`),
  KEY `renew_price_year_total_idx` (`renew_price_total`),
  KEY `renew_cost_year_total_idx` (`renew_cost_total`),
  KEY `date_fact` (`date_fact`) USING BTREE,
  CONSTRAINT `purchase_person_fk` FOREIGN KEY (`person_id`) REFERENCES `person` (`person_id`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  CONSTRAINT `purchase_person_owner_fk` FOREIGN KEY (`person_id_owner`) REFERENCES `person` (`person_id`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  CONSTRAINT `purchase_service_fk` FOREIGN KEY (`service_id`) REFERENCES `service` (`service_id`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

我正在啟動此查詢：

SELECT 
    purchase.date_fact,
    UNIX_TIMESTAMP(purchase.date_fact),
    COUNT(DISTINCT purchase.purchase_id) AS Num
FROM
    purchase
WHERE
    purchase.date_fact >= '2017-01-01'
    AND purchase.date_fact <= '2017-01-31'
    AND purchase.fact_type = 3
    AND purchase.purchase_id_primary IS NULL
GROUP BY purchase.date_fact

該表總共包含5.629.670條記錄，並對查詢運行EXPLAIN會得到以下結果：

• rows = 2.814.835
• possible_keys = fact_type_idx,purchase_id_primary_idx,date_fact
• key = fact_type_idx
• key_len = 1
• ref = const
• filtered = 25.00
• Extra = Using index condition;Using where;Using filesort

查詢需要30-35秒才能執行。 等待時間太長。

問題是GROUP BY導致要應用文件排序。 將ORDER BY NULL應用於查詢不會改變任何東西 。

我可以使用覆蓋索引，但是在此查詢中我只需要使用date_fact：我可以使用哪些字段？

如何避免對GROUP BY排序？ 如何優化查詢以使其更快？

我將此表用於統計目的（OLAP）。 也許為此目的有更好的DBMS嗎？

我正在運行MySql Server 5.7.17。

謝謝

Answer 1

對於此查詢：

SELECT p.date_fact, UNIX_TIMESTAMP(p.date_fact),
       COUNT(DISTINCT p.purchase_id) AS Num
FROM purchase p
WHERE p.date_fact >= '2017-01-01' AND
      p.date_fact <= '2017-01-31' AND
      p.fact_type = 3 AND
      p.purchase_id_primary IS NULL
GROUP BY p.date_fact;

我建議在(fact_type, purchase_id_primary, date_fact, purchase_id)上使用復合索引。 前兩個鍵在WHERE具有相等條件。 第三個具有不等式，第四個允許索引“覆蓋”查詢（查詢中的所有列都在索引中）。

我還要補充一句：如果您不需要COUNT(DISTINCT) ，請不要使用它。 purchase_id可能已經是唯一的purchase 。