mysql 左连接全文搜索很慢

Question

我有 2 个表:带有单词示例的单词。大约有 7 万个单词，大约有 100 万个示例。我尝试添加带有搜索和分页结果的管理员，但遇到查询需要 6-7 秒才能生成结果。
我做错了什么吗？

这是架构:

```
CREATE TABLE IF NOT EXISTS words (
    id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
    word VARCHAR(191) DEFAULT NULL,
    fl VARCHAR(191) DEFAULT NULL,
    UNIQUE KEY (word, fl),
    FULLTEXT (word)
    PRIMARY KEY (id)
) ENGINE=InnoDB DEFAULT CHARACTER SET utf8mb4 DEFAULT COLLATE utf8mb4_unicode_ci;


CREATE TABLE IF NOT EXISTS examples (
    id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
    fk_words_id BIGINT UNSIGNED,
    src VARCHAR(50) DEFAULT NULL,
    example VARCHAR(400) DEFAULT NULL,
    cite_author VARCHAR(400) DEFAULT NULL,
    cite_publication VARCHAR(400) DEFAULT NULL,
    cite_title VARCHAR(400) DEFAULT NULL,
    FULLTEXT (example,cite_author,cite_publication),
    PRIMARY KEY (id),
    FOREIGN KEY (fk_words_id) REFERENCES words (id) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB DEFAULT CHARACTER SET utf8mb4 DEFAULT COLLATE utf8mb4_unicode_ci;
```

我对分页结果的查询如下所示:

SELECT DISTINCT 
a.id,
a.word,
a.fl,
a.updated
FROM words AS a
LEFT JOIN examples AS b
ON a.id = b.fk_words_id
WHERE (a.word = :search_string OR MATCH(b.example,b.cite_author,b.cite_publication) AGAINST(+'some word' IN BOOLEAN MODE))
ORDER BY id asc
LIMIT 0,20;

有什么办法可以提高性能吗？

Answer 1

我建议如下。对一列执行 b 上的不同操作应该比执行左连接然后对 4 列执行不同操作更快。

SELECT
      a.id
    , a.word
    , a.fl
    , a.updated
FROM words AS a
LEFT JOIN (
      SELECT DISTINCT fk_words_id FROM examples
      WHERE MATCH(b.example,b.cite_author,b.cite_publication) AGAINST(+'some word' IN BOOLEAN MODE))
      ) b ON a.id = b.fk_words_id
WHERE a.word = :search_string
ORDER BY
      id ASC
LIMIT 0,20;