SQL 查询需要永远运行答案

【问题标题】：SQL query takes forever to runSQL 查询需要永远运行
【发布时间】：2020-09-07 11:22:59
【问题描述】：

几天前我有一个小型数据库时写了一些查询，一切都很好。但是，从那时起，数据库的大小一直在增长，现在它需要大量的时间来运行。有什么方法可以让这个查询运行得更快？

explain SELECT  job.id,  job_title, text_job_description, html_job_description, amp_html_job_desc, destination, created_at,  org.id, org.name, org.logo
FROM jobs.job as job  LEFT OUTER JOIN
     jobs.organization as org
     ON job.organization_id = org.id
WHERE job.is_expired = 0 and job.is_hidden = 0 and 
      deleted_at is NULL
order by job.created_at desc
offset 0 limit 20;

                                         QUERY PLAN                                          
---------------------------------------------------------------------------------------------
 Limit  (cost=10514.03..10514.08 rows=20 width=1456)
   ->  Sort  (cost=10514.03..10594.67 rows=32258 width=1456)
         Sort Key: job.created_at DESC
         ->  Hash Left Join  (cost=1.20..9655.65 rows=32258 width=1456)
               Hash Cond: (job.organization_id = org.id)
               ->  Seq Scan on job  (cost=0.00..9529.90 rows=32258 width=1384)
                     Filter: ((deleted_at IS NULL) AND (is_expired = 0) AND (is_hidden = 0))
               ->  Hash  (cost=1.09..1.09 rows=9 width=72)
                     ->  Seq Scan on organization org  (cost=0.00..1.09 rows=9 width=72)

【问题讨论】：

你能发布一个现有表的所有索引的列表吗？
@FelipeValdes 工作表的索引是 currency_id job_category_id organization_id resource_id user_id doc_vectors deleted_at is_expired is_hidden organization_id

标签： sql postgresql query-performance

【解决方案1】：

大概，您的查询是：

SELECT . . .
FROM jobs.job j LEFT OUTER JOIN
     jobs.organization o
     ON j.organization_id = o.id
WHERE j.is_expired = 0 and j.is_hidden = 0 and 
      j.deleted_at is NULL
------^ not identified in your query
ORDER BY j.created_at desc
OFFSET 0 LIMIT 20;

如果是这样，您需要在 (job(is_expired, is_hidden, deled_at, created_at, organization_id) 和 organization(id) 上建立索引。如果将id 定义为主键，则可能不需要后者。

【讨论】：