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有 max_join_size = 300M 的 MariaDB 10.4.14 和内部有约 150,000 条记录的硬币 InnoDB 表。

一个足够简单的查询会产生 MAX_JOIN_SIZE 错误：

SELECT * FROM coin z -- USE INDEX(PRIMARY)
WHERE z.id IN (5510, 5511, 5512 /* more item IDs up to 250 */)
  AND z.currency_id IN (8, 227)
  AND z.distribution_id IN (1, 2);

Error Code: 1104
The SELECT would examine more than MAX_JOIN_SIZE rows; check your WHERE and use SET SQL_BIG_SELECTS=1 or SET MAX_JOIN_SIZE=# if the SELECT is okay

但是带有索引提示的相同查询效果很好。命中 ["PRIMARY", "currency_id_idx", "distribution_id"] 甚至 issue_date_idx 中的哪个索引都没有关系，即使没有索引也可以使用 USE INDEX()。

这里有什么问题？为什么在没有提示的情况下查询不起作用？

顺便说一句，这个查询在 MariaDB 10.3.24 上运行良好，在 10.5.5 上不运行

OPTIMIZE TABLE coin; -- didn't help

Table DDL and query EXPLAIN
CREATE TABLE `coin` (
  `id` mediumint(8) unsigned NOT NULL AUTO_INCREMENT,
  `name` varchar(90) NOT NULL DEFAULT '',
  `country_id` smallint(5) unsigned NOT NULL DEFAULT 0,
  `currency_id` smallint(5) unsigned NOT NULL DEFAULT 0,
  `distribution_id` tinyint(3) unsigned NOT NULL,
  `issue_date` date NOT NULL DEFAULT '0000-00-00',
  -- and other, total 29 fields
  PRIMARY KEY (`id`),
  KEY `issue_date_idx` (`issue_date`),
  KEY `currency_id_idx` (`currency_id`),
  KEY `distribution_id` (`distribution_id`),
  -- and other, total 21 indices for other fields which don't use currency_id or distribution_id
  CONSTRAINT `coin_ibfk_4` FOREIGN KEY (`currency_id`) REFERENCES `currency` (`id`),
  CONSTRAINT `coin_ibfk_11` FOREIGN KEY (`distribution_id`) REFERENCES `distribution` (`id`),
  -- and other, total 13 CONSTRAINTs
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci

EXPLAIN FORMAT=JSON -- for SELECT above without index hint
{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "z",
      "access_type": "range",
      "possible_keys": ["PRIMARY", "currency_id_idx", "distribution_id"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["id"],
      "rows": 50,
      "filtered": 100,
      "attached_condition": "z.`id` in (5510,5511,5512, /* ... total 100 */) and z.currency_id in (8,227) and z.distribution_id in (1,2)"
    }
  }
}

上面的 SELECT 可以在没有索引提示的情况下使用最大可能的 MAX_JOIN_SIZE 值，并且没有最大值 - 1：

SET MAX_JOIN_SIZE=18446744073709551615 -- this works
SET MAX_JOIN_SIZE=18446744073709551614 -- this doesn't work
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1 回答 1

0

可以通过恢复以前的默认值来修复 MAX_JOIN_SIZE 错误

optimizer_use_condition_selectivity = 1 # new default is 4 since 10.4.1
于 2020-10-07T18:31:33.437 回答