馴服一個怪物MySQL查詢

Question

因此，通過一些SO用戶的幫助，我最終得到了一個邏輯上正確的MySQL查詢，用於我正在處理的任務：檢索反向按時間順序排列的ID列表允許用戶使用的新聞項目，某些類型的分組項目過濾到該組的單個代表。 （Phew！）

還有一個明顯的問題，就是根據CakePHP的數據庫調用調試打印輸出，這個查詢非常笨重且速度很慢，達到了145000毫秒，哎。

是否有一個明智的辦法來馴服野獸像這樣的，或者我應該承認，我貪多，我可以在這裏咀嚼，尋找一個不太沉重的方法，將實現更多或更少類似的結果？所有建議表示讚賞

SELECT DISTINCT Uid.id, Uid.type 
    FROM (SELECT uids.id id, uids_uids.parent_id parent_id, uids.created date, 
       uids.type type 
      FROM uids 
      JOIN uids_uids ON uids_uids.uid_id = uids.id 
      JOIN aros_uids ON uids.id = aros_uids.uid_id 
      JOIN uids_uids ParentUids ON uids_uids.parent_id = ParentUids.uid_id 
      WHERE uids.type IN ('Document','Photo','Release','PreRelease', 
           'ArtworkResource','Event') 
      AND (uids.start_date IS NULL OR uids.start_date <= NOW()) 
      AND (uids.end_date IS NULL OR uids.end_date <= NOW()) 
      AND aros_uids.aro_id IN (3,2,86,1448) 
     ) Uid 
    JOIN (SELECT uids_uids.parent_id parent_id, MAX(uids.created) maxdate 
      FROM uids JOIN uids_uids 
      ON uids_uids.uid_id = uids.id 
      GROUP BY uids_uids.parent_id, uids.type) T2 
    ON Uid.parent_id = T2.parent_id AND Uid.date = T2.maxdate 
    ORDER BY Uid.date DESC 
    LIMIT 100 

ETA：

好了，在第一遍，我轉身的子查詢到意見，所以現在查詢看起來像一個稍微更易於管理

SELECT DISTINCT Uid.id, Uid.type 
    FROM UidView Uid 
    JOIN UidView2 T2 
    ON Uid.parent_id = T2.parent_id AND Uid.date = T2.maxdate 
    WHERE Uid.aro_id IN (3,2,86,1448) 
    ORDER BY Uid.date DESC 
    LIMIT 100 

這一定幫助，將Cake的估計查詢時間從六位數降低到2500位左右。絕對是一個好開始！

Answer 1

這裏是我想嘗試：

以每個派生的查詢和獨立運行的EXPLAIN針對每個。如評論所示，檢查任何缺少索引並在需要時添加的行。發佈您的EXPLAIN結果以獲得任何幫助。所以

EXPLAIN SELECT uids.id id, uids_uids.parent_id parent_id, uids.created date, .... 
EXPLAIN SELECT uids_uids.parent_id parent_id, MAX(uids.created) maxdate .... 

如果添加索引不幫助或幫助不大，然後把每個子查詢到一個臨時表第一，並應用指標到它：這些表

CREATE TABLE temp_uid 
SELECT uids.id id, uids_uids.parent_id parent_id, uids.created date, 
      uids.type type 
     FROM uids 
     JOIN uids_uids ON uids_uids.uid_id = uids.id 
     JOIN aros_uids ON uids.id = aros_uids.uid_id 
     JOIN uids_uids ParentUids ON uids_uids.parent_id = ParentUids.uid_id 
     WHERE uids.type IN ('Document','Photo','Release','PreRelease', 
          'ArtworkResource','Event') 
     AND (uids.start_date IS NULL OR uids.start_date <= NOW()) 
     AND (uids.end_date IS NULL OR uids.end_date <= NOW()) 
     AND aros_uids.aro_id IN (3,2,86,1448); 

CREATE TABLE temp_t2 
SELECT uids_uids.parent_id parent_id, MAX(uids.created) maxdate 
     FROM uids JOIN uids_uids 
     ON uids_uids.uid_id = uids.id 
     GROUP BY uids_uids.parent_id, uids.type; 

而且JOIN：

SELECT DISTINCT Uid.id, Uid.type 
FROM temp_uid AS Uid 
JOIN temp_t2 AS T2 ON Uid.parent_id = T2.parent_id AND Uid.date = T2.maxdate 
ORDER BY Uid.date DESC 
LIMIT 100; 

正如我所提到的，您可能需要添加索引，並且可能會添加到臨時表中的這些列中：

ALTER TABLE temp_uid ADD INDEX parentDateIdx (parent_id, Uid.date); 
ALTER TABLE temp_t2 ADD INDEX parentMaxDateIdx (parent_id, maxdate); 

如果您需要刷新臨時表，只需截斷它們並對它們執行INSERT INTO temp_uid...SELECT和INSERT INTO temp_t2...SELECT而不是CREATE...SELECT。存儲過程對此非常有用。

順便說一句，執行CREATE TABLE temp_t2...SELECT，我爲每個臨時表執行的方式可能無法創建最佳表結構，因此最好修改後續創建或從頭開始自己完成。