Rails查詢與包括需要很長的時間

公司表= 280K行

PostIndex表= 3.1k行

CompanyCategory = 5行

查詢看起來是這樣的：

query = '' 
associations = [:post_index, :company_category] 
Company.includes(associations).references(associations).where(query).order(:id).limit(25)

爲了簡化問題，讓我們坐在這個查詢是空字符串。另外我有相關記錄的索引。

這個查詢加載時間= 1.2-1.3秒，即使是空的條件。並且最多2秒鐘不空查詢。

如何加快此查詢？

事件這個簡單的查詢需要250ms的加載： Company.find_by(name: 'asd')

是否elasticsearch（或類似）是在我的情況下，唯一的解決辦法？

PS我不能使用內部連接，因爲並不是所有的企業都post_index

感謝您的幫助提前

更新1

只是意識到上面的查詢需要約1.3秒指定的順序和6毫秒沒有指定的順序。即使我按索引列（例如'companies.id'）排序，它仍然很慢，需要1.3秒。有什麼建議麼？

更新2

我試着做了解釋疑問，這裏是結果：

Explain query （http://i.stack.imgur.com/VzKE6.png）

我檢查的模式，我有分類與PostIndices指標有：

add_index "companies", ["company_category_id"], name: "index_companies_on_company_category_id", using: :btree 
add_index "companies", ["post_index_id"], name: "index_companies_on_post_index_id", using: :btree

indexes （http://i.stack.imgur.com/eInwr.png）

對於這兩個模型，與公司模型的關係完全相同。但相應的解釋，它表現不同。我不熟悉EXPLAIN，但從我讀過的內容 - 加入類別時，加入類型是ALL，這是不好的。它搜索138632 * 5行。

但是，當加入PostIndex時，加入類型是eq_ref，所以它搜索138632 * 1行。所以我完全困惑爲什麼會發生這種情況。任何想法？

UPDATE 4

SHOW CREATE TABLE公司;

enter image description here （http://i.stack.imgur.com/E6CEO.png）

UPDATE 5

SLOW RUBY：

Company.includes(associations).references(associations).where(query).order(:id).limit(25).explain

SLOW SQL：

SELECT `companies`.`id` AS t0_r0, `companies`.`name` AS t0_r1, 
     `companies`.`address` AS t0_r2, `companies`.`post_index_id` AS t0_r3, 
     `companies`.`tel` AS t0_r4, `companies`.`mobile` AS t0_r5, 
     `companies`.`fax` AS t0_r6, `companies`.`email` AS t0_r7, 
     `companies`.`website` AS t0_r8, `companies`.`vat` AS t0_r9, 
     `companies`.`company_category_id` AS t0_r10, `companies`.`nace` AS t0_r11, 
     `companies`.`union` AS t0_r12, `companies`.`note` AS t0_r13, 
     `companies`.`created_at` AS t0_r14, `companies`.`updated_at` AS t0_r15, 
     `companies`.`ean` AS t0_r16, `companies`.`deleted_at` AS t0_r17, 
     `companies`.`sector` AS t0_r18, `companies`.`status` AS t0_r19, 
     `post_indices`.`id` AS t1_r0, `post_indices`.`county` AS t1_r1, 
     `post_indices`.`postal_code` AS t1_r2, `post_indices`.`group_part` AS t1_r3, 
     `post_indices`.`group_number` AS t1_r4, `post_indices`.`group_name` AS t1_r5, 
     `post_indices`.`city` AS t1_r6, `post_indices`.`created_at` AS t1_r7, 
     `post_indices`.`updated_at` AS t1_r8, 
     -- EXTRA: 
     `company_categories`.`id` AS t2_r0, 
     `company_categories`.`name` AS t2_r1, `company_categories`.`created_at` AS t2_r2, 
     `company_categories`.`updated_at` AS t2_r3 
     -- END EXTRA 
    FROM `companies` 
    LEFT OUTER JOIN `post_indices` ON `post_indices`.`id` = `companies`.`post_index_id` 
     -- EXTRA: 
    LEFT OUTER JOIN `company_categories` ON `company_categories`.`id` = `companies`.`company_category_id` 
     -- END EXTRA 
    WHERE `companies`.`deleted_at` IS NULL 
    ORDER BY `companies`.`id` ASC 
    LIMIT 25

FAST RUBY：

Company.includes(associations.first).references(associations.first).where(query).order(:id).limit(25).explain

FAST SQL：

SELECT `companies`.`id` AS t0_r0, `companies`.`name` AS t0_r1, 
     `companies`.`address` AS t0_r2, `companies`.`post_index_id` AS t0_r3, 
     `companies`.`tel` AS t0_r4, `companies`.`mobile` AS t0_r5, 
     `companies`.`fax` AS t0_r6, `companies`.`email` AS t0_r7, 
     `companies`.`website` AS t0_r8, `companies`.`vat` AS t0_r9, 
     `companies`.`company_category_id` AS t0_r10, `companies`.`nace` AS t0_r11, 
     `companies`.`union` AS t0_r12, `companies`.`note` AS t0_r13, 
     `companies`.`created_at` AS t0_r14, `companies`.`updated_at` AS t0_r15, 
     `companies`.`ean` AS t0_r16, `companies`.`deleted_at` AS t0_r17, 
     `companies`.`sector` AS t0_r18, `companies`.`status` AS t0_r19, 
     `post_indices`.`id` AS t1_r0, `post_indices`.`county` AS t1_r1, 
     `post_indices`.`postal_code` AS t1_r2, `post_indices`.`group_part` AS t1_r3, 
     `post_indices`.`group_number` AS t1_r4, `post_indices`.`group_name` AS t1_r5, 
     `post_indices`.`city` AS t1_r6, `post_indices`.`created_at` AS t1_r7, 
     `post_indices`.`updated_at` AS t1_r8 
    FROM `companies` 
    LEFT OUTER JOIN `post_indices` ON `post_indices`.`id` = `companies`.`post_index_id` 
    WHERE `companies`.`deleted_at` IS NULL 
    ORDER BY `companies`.`id` ASC 
    LIMIT 25

enter image description here （http://i.stack.imgur.com/NhpaX.png）