SQL-查詢運行非常緩慢

Question

我有如下表關系：

我從php運行以下查詢，並遇到兩個大問題。
1）超出最大內存限制
2）超過最大執行時間

SELECT DISTINCT venues.name, locations.location, events.event, types.type, foods.food, beverages.beverage, event_options.event_option, styles.style, space_requirements.space_requirement, features.feature

FROM (SELECT * FROM venues v LIMIT $offset,$limit) venues

INNER JOIN locations ON venues.location_id = locations.location_id

LEFT JOIN venue_events ON venues.venue_id = venue_events.venue_id
LEFT JOIN events ON events.event_id = venue_events.event_id

LEFT JOIN venue_types ON venues.venue_id = venue_types.venue_id
LEFT JOIN types ON types.type_id = venue_types.type_id

LEFT JOIN venue_foods ON venues.venue_id = venue_foods.venue_id
LEFT JOIN foods ON foods.food_id = venue_foods.food_id

LEFT JOIN venue_beverages ON venues.venue_id = venue_beverages.venue_id
LEFT JOIN beverages ON beverages.beverage_id = venue_beverages.beverage_id

LEFT JOIN venue_event_options ON venues.venue_id = venue_event_options.venue_id
LEFT JOIN event_options ON event_options.event_option_id = venue_event_options.event_option_id

LEFT JOIN venue_styles ON venues.venue_id = venue_styles.venue_id
LEFT JOIN styles ON styles.style_id = venue_styles.style_id

LEFT JOIN venue_space_requirements ON venues.venue_id = venue_space_requirements.venue_id
LEFT JOIN space_requirements ON space_requirements.space_requirement_id = venue_space_requirements.space_requirement_id

LEFT JOIN venue_features ON venues.venue_id = venue_features.venue_id
LEFT JOIN features ON features.feature_id = venue_features.feature_id

我正在使用此查詢來檢索與每個場所有關的所有配件。 我需要在后端實現分頁，所以我在子查詢中使用LIMIT $ offset，$ limit。 我找不到其他想法（查詢），因此可以實現與我現在正在檢索的結果相同的結果。 目前我正在使用

ini_set('memory_limit', '-1');
ini_set('max_execution_time', 60);

php函數會忽略這些問題，但是我認為這不是最佳實踐。 我也在考慮可能需要檢索50多個場所的所有配件的情況，對於這些配件， max_execution_time = 60可能還不夠。

我如何擺脫這個問題？ 請幫我。

更新
獲取的行數是每個場所都有的（事件*類型*食物*飲料* event_options *樣式* space_requirements *功能）。 但是對我有用的行數不是乘法，而是總和。

這是我使用EXPLAIN關鍵字運行查詢后發現的結果

Array
(
    [0] => Array
        (
            [id] => 1
            [select_type] => PRIMARY
            [table] => 
            [type] => ALL
            [possible_keys] => 
            [key] => 
            [key_len] => 
            [ref] => 
            [rows] => 11
            [Extra] => Using temporary
        )

    [1] => Array
        (
            [id] => 1
            [select_type] => PRIMARY
            [table] => venue_events
            [type] => ref
            [possible_keys] => PRIMARY
            [key] => PRIMARY
            [key_len] => 4
            [ref] => venues.venue_id
            [rows] => 3
            [Extra] => Using index
        )

    [2] => Array
        (
            [id] => 1
            [select_type] => PRIMARY
            [table] => events
            [type] => eq_ref
            [possible_keys] => PRIMARY
            [key] => PRIMARY
            [key_len] => 1
            [ref] => serofero_mvb.venue_events.event_id
            [rows] => 1
            [Extra] => 
        )

    [3] => Array
        (
            [id] => 1
            [select_type] => PRIMARY
            [table] => venue_types
            [type] => ref
            [possible_keys] => PRIMARY
            [key] => PRIMARY
            [key_len] => 4
            [ref] => venues.venue_id
            [rows] => 7
            [Extra] => Using index
        )

    [4] => Array
        (
            [id] => 1
            [select_type] => PRIMARY
            [table] => types
            [type] => eq_ref
            [possible_keys] => PRIMARY
            [key] => PRIMARY
            [key_len] => 1
            [ref] => serofero_mvb.venue_types.type_id
            [rows] => 1
            [Extra] => 
        )

    [5] => Array
        (
            [id] => 1
            [select_type] => PRIMARY
            [table] => venue_foods
            [type] => ref
            [possible_keys] => PRIMARY
            [key] => PRIMARY
            [key_len] => 4
            [ref] => venues.venue_id
            [rows] => 3
            [Extra] => Using index
        )

    [6] => Array
        (
            [id] => 1
            [select_type] => PRIMARY
            [table] => foods
            [type] => eq_ref
            [possible_keys] => PRIMARY
            [key] => PRIMARY
            [key_len] => 1
            [ref] => serofero_mvb.venue_foods.food_id
            [rows] => 1
            [Extra] => Using index
        )

    [7] => Array
        (
            [id] => 1
            [select_type] => PRIMARY
            [table] => venue_beverages
            [type] => ref
            [possible_keys] => PRIMARY
            [key] => PRIMARY
            [key_len] => 4
            [ref] => venues.venue_id
            [rows] => 3
            [Extra] => Using index
        )

    [8] => Array
        (
            [id] => 1
            [select_type] => PRIMARY
            [table] => beverages
            [type] => eq_ref
            [possible_keys] => PRIMARY
            [key] => PRIMARY
            [key_len] => 1
            [ref] => serofero_mvb.venue_beverages.beverage_id
            [rows] => 1
            [Extra] => 
        )

    [9] => Array
        (
            [id] => 1
            [select_type] => PRIMARY
            [table] => venue_event_options
            [type] => ref
            [possible_keys] => PRIMARY
            [key] => PRIMARY
            [key_len] => 4
            [ref] => venues.venue_id
            [rows] => 2
            [Extra] => Using index
        )

    [10] => Array
        (
            [id] => 1
            [select_type] => PRIMARY
            [table] => event_options
            [type] => eq_ref
            [possible_keys] => PRIMARY
            [key] => PRIMARY
            [key_len] => 1
            [ref] => serofero_mvb.venue_event_options.event_option_id
            [rows] => 1
            [Extra] => 
        )

    [11] => Array
        (
            [id] => 1
            [select_type] => PRIMARY
            [table] => venue_styles
            [type] => ref
            [possible_keys] => PRIMARY
            [key] => PRIMARY
            [key_len] => 4
            [ref] => venues.venue_id
            [rows] => 1
            [Extra] => Using index
        )

    [12] => Array
        (
            [id] => 1
            [select_type] => PRIMARY
            [table] => styles
            [type] => eq_ref
            [possible_keys] => PRIMARY
            [key] => PRIMARY
            [key_len] => 1
            [ref] => serofero_mvb.venue_styles.style_id
            [rows] => 1
            [Extra] => 
        )

    [13] => Array
        (
            [id] => 1
            [select_type] => PRIMARY
            [table] => venue_space_requirements
            [type] => ref
            [possible_keys] => PRIMARY
            [key] => PRIMARY
            [key_len] => 4
            [ref] => venues.venue_id
            [rows] => 3
            [Extra] => Using index
        )

    [14] => Array
        (
            [id] => 1
            [select_type] => PRIMARY
            [table] => space_requirements
            [type] => eq_ref
            [possible_keys] => PRIMARY
            [key] => PRIMARY
            [key_len] => 1
            [ref] => serofero_mvb.venue_space_requirements.space_requirement_id
            [rows] => 1
            [Extra] => 
        )

    [15] => Array
        (
            [id] => 1
            [select_type] => PRIMARY
            [table] => locations
            [type] => eq_ref
            [possible_keys] => PRIMARY
            [key] => PRIMARY
            [key_len] => 1
            [ref] => venues.location_id
            [rows] => 1
            [Extra] => 
        )

    [16] => Array
        (
            [id] => 1
            [select_type] => PRIMARY
            [table] => venue_features
            [type] => ref
            [possible_keys] => PRIMARY
            [key] => PRIMARY
            [key_len] => 4
            [ref] => venues.venue_id
            [rows] => 7
            [Extra] => Using index
        )

    [17] => Array
        (
            [id] => 1
            [select_type] => PRIMARY
            [table] => features
            [type] => eq_ref
            [possible_keys] => PRIMARY
            [key] => PRIMARY
            [key_len] => 1
            [ref] => serofero_mvb.venue_features.feature_id
            [rows] => 1
            [Extra] => 
        )

    [18] => Array
        (
            [id] => 2
            [select_type] => DERIVED
            [table] => venues
            [type] => ALL
            [possible_keys] => 
            [key] => 
            [key_len] => 
            [ref] => 
            [rows] => 11
            [Extra] => 
        )

)

謝謝

Answer 1

為您選擇的列創建索引。

Answer 2

您需要將查詢更改為以下內容；

SELECT DISTINCT venues.`name`, locations.`location`, events.`event`, types.`type`, foods.`food`, beverages.`beverage`, event_options.`event_option`, styles.`style`, space_requirements.`space_requirement`, features.`feature`

請記住，這只是代碼的第一行。 您需要在查詢的任何地方進行更改。

由於出現此錯誤的原因是索引丟失，因此將以正確的方式定義索引，並且php易於區分。

Answer 3

根據EXPLAIN輸出，似乎查詢已在使用PRIMARY KEY作為索引。 您為什么不嘗試拆分查詢。

首先，獲取要顯示（分頁）的場所的ID。

SELECT id FROM venues v LIMIT $offset,$limit

$venue_ids = implode(',', $results);

接下來，運行此查詢。

SELECT DISTINCT venues.name, locations.location, events.event, types.type, foods.food, beverages.beverage, event_options.event_option, styles.style, space_requirements.space_requirement, features.feature

FROM venues

INNER JOIN locations ON venues.location_id = locations.location_id

LEFT JOIN venue_events ON venues.venue_id = venue_events.venue_id
LEFT JOIN events ON events.event_id = venue_events.event_id

LEFT JOIN venue_types ON venues.venue_id = venue_types.venue_id
LEFT JOIN types ON types.type_id = venue_types.type_id

LEFT JOIN venue_foods ON venues.venue_id = venue_foods.venue_id
LEFT JOIN foods ON foods.food_id = venue_foods.food_id

LEFT JOIN venue_beverages ON venues.venue_id = venue_beverages.venue_id
LEFT JOIN beverages ON beverages.beverage_id = venue_beverages.beverage_id

LEFT JOIN venue_event_options ON venues.venue_id = venue_event_options.venue_id
LEFT JOIN event_options ON event_options.event_option_id = venue_event_options.event_option_id

LEFT JOIN venue_styles ON venues.venue_id = venue_styles.venue_id
LEFT JOIN styles ON styles.style_id = venue_styles.style_id

LEFT JOIN venue_space_requirements ON venues.venue_id = venue_space_requirements.venue_id
LEFT JOIN space_requirements ON space_requirements.space_requirement_id = venue_space_requirements.space_requirement_id

LEFT JOIN venue_features ON venues.venue_id = venue_features.venue_id
LEFT JOIN features ON features.feature_id = venue_features.feature_id

WHERE venues.id IN ( $venue_ids )

那至少應該擺脫派生表。