當另一個表變得更加完整時，sql查詢非常緩慢

Question

我有以下查詢，但是過了一段時間，用戶開始在「ci_falsepositives」表中放入越來越多的項目時，它變得非常慢。 ci_falsepositives表包含來自ci_address_book的引用字段和來自ci_matched_sanctions的另一個引用字段。

如何創建新的查詢，但仍然能夠在每個字段上進行排序。 例如，我仍然可以排序的「點擊率」或「匹配」

SELECT *, matches - falsepositives AS hits 
    FROM (SELECT c.*, IFNULL(p.total, 0) AS matches, 
       (SELECT COUNT(*) 
        FROM ci_falsepositives n 
       WHERE n.addressbook_id = c.reference 
        AND n.sanction_key IN 
         (SELECT sanction_key FROM ci_matched_sanctions) 
       ) AS falsepositives 
      FROM ci_address_book c 
      LEFT JOIN 
       (SELECT addressbook_id, COUNT(match_id) AS total 
        FROM ci_matched_sanctions 
       GROUP BY addressbook_id) AS p 
      ON c.id = p.addressbook_id 
     ) S 
ORDER BY folder asc, wholename ASC 
LIMIT 0,15 

Answer 1

的問題必須是SELECT COUNT(*) FROM ci_falsepositives子查詢。該子查詢可以使用ci_falsepositives和ci_matched_sanctions之間的內部聯接編寫，但優化程序可能會爲您做到這一點。但是，我認爲您需要做的是在「下一個查詢」（即SELECT c.*, ...）的FROM子句中將該子查詢放入單獨的查詢中。很可能，該查詢正在被多次評估 - 當人們將記錄添加到ci_falsepositives時，這就是傷害你的原因。您應該仔細研究查詢計劃。

也許這查詢會更好：

SELECT *, matches - falsepositives AS hits 
    FROM (SELECT c.*, IFNULL(p.total, 0) AS matches, f.falsepositives 
      FROM ci_address_book AS c 
      JOIN (SELECT n.addressbook_id, COUNT(*) AS falsepositives 
        FROM ci_falsepositives AS n 
        JOIN ci_matched_sanctions AS m 
        ON n.sanction_key = m.sanction_key 
       GROUP BY n.addressbook_id 
       ) AS f 
      ON c.reference = f.addressbook_id 
      LEFT JOIN 
       (SELECT addressbook_id, COUNT(match_id) AS total 
        FROM ci_matched_sanctions 
       GROUP BY addressbook_id) AS p 
      ON c.id = p.addressbook_id 
     ) AS s 
ORDER BY folder asc, wholename ASC 
LIMIT 0, 15