我需要添加哪些索引来加快此MYSQL JOIN / GROUP BY / HAVING查询的速度？

Question

The following query takes about 30 seconds to execute when current_vacature_response contains 88k records, and daily_vacature_response contains 10k records. Using EXPLAIN I've concluded that no indexes where used from the current_vacature_response table. I've added some basic indexes, but none of them seem to be used. What kind of index do I need to set to speed up this query?

Query:

SELECT c.`stats_date` as `stats_date` 
    FROM `current_vacature_response` c 
    LEFT JOIN `daily_vacature_response` d ON (c.`stats_date` = d.`stats_date` )
    GROUP BY c.`stats_date`, d.`stats_date` 
    HAVING max(d.`last_stats_datetime`) IS NULL 
        OR MAX(d.`last_stats_datetime`) < MAX(c.`created_datetime`);

current_vacature_response table definition:

CREATE TABLE `current_vacature_response` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `created_datetime` datetime NOT NULL,
  `site_id` tinyint(1) unsigned NOT NULL,
  `stats_date` date NOT NULL,
  `type` enum('typ1', 'type2') NOT NULL,
  `vacature` int(10) unsigned NOT NULL,
  PRIMARY KEY (`id`),
  KEY `current_vacature_created_datetime` (`created_datetime`),
  KEY `current_vacature_response_vacature` (`vacature`),
  KEY `current_vacature_response_type` (`type`),
  KEY `current_vacature_stats_date` (`stats_date`)
) ENGINE=MyISAM AUTO_INCREMENT=88210 DEFAULT CHARSET=utf8;

daily_vacature_response table definition:

CREATE TABLE `daily_vacature_response` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `contact` int(10) unsigned NOT NULL DEFAULT '0',
  `site_id` tinyint(1) unsigned NOT NULL,
  `spotlight_result` int(10) unsigned NOT NULL DEFAULT '0',
  `stats_date` date NOT NULL,
  `last_stats_datetime` datetime NOT NULL,
  `vacature` int(10) unsigned NOT NULL,
  `created_datetime` datetime NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `daily_vacature_response_key` (`site_id`,`vacature`,`stats_date`),
  KEY `daily_vacature_response_last_stats_datetime` (`last_stats_datetime`),
  KEY `daily_vacature_response_stats_date` (`stats_date`)
) ENGINE=MyISAM AUTO_INCREMENT=9802 DEFAULT CHARSET=utf8;

Explain output:

*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: c
         type: ALL
possible_keys: NULL
          key: NULL
      key_len: NULL
          ref: NULL
         rows: 88209
        Extra: Using temporary; Using filesort
*************************** 2. row ***************************
           id: 1
  select_type: SIMPLE
        table: d
         type: ref
possible_keys: daily_vacature_response_stats_date
          key: daily_vacature_response_stats_date
      key_len: 3
          ref: reporting_development.c.stats_date
         rows: 99
        Extra: 

Answer 1

Try an index on daily_vacature_response(stats_date, last_stats_datetime) .

I'm suspicious that it'll make a huge difference, but that's the most likely candidate.

Also, try rewriting the query a little bit (might not work in MySQL, but worth trying):

GROUP BY c.`stats_date`, c.`created_datetime`, d.`stats_date` 
HAVING max(d.`last_stats_datetime`) IS NULL 
    OR max(d.`last_stats_datetime`) < c.`created_datetime`;