Re: Postgres 9 : - How to interpret the EXPLAIN query results

Поиск
Список
Период
Сортировка
От Khangelani Gama
Тема Re: Postgres 9 : - How to interpret the EXPLAIN query results
Дата
Msg-id 80b319b3f6696a7f1672a4640f55e803@mail.gmail.com
обсуждение исходный текст
Ответ на Re: Postgres 9 : - How to interpret the EXPLAIN query results  (Raghavendra <raghavendra.rao@enterprisedb.com>)
Ответы Re: Postgres 9 : - How to interpret the EXPLAIN query results  (Thomas Kellerer <spam_eater@gmx.net>)
Список pgsql-admin
Дерево обсуждения

 

 

From: Raghavendra [mailto:raghavendra.rao@enterprisedb.com]
Sent: 25 March 2015 12:04 PM
To: Khangelani Gama
Cc: pgsql-admin
Subject: Re: [ADMIN] Postgres 9 : - How to interpret the EXPLAIN query results

 

On Wed, Mar 25, 2015 at 1:30 PM, Khangelani Gama <kgama@argility.com> wrote:

Hi

 

Please help, how can I interpret the following results of my EXPLAIN query ?, I can see that the query will through 18586018 rows, but what’s the meaning of cost and width? 

  

GroupAggregate  (cost=762381141.96..768375132.77 rows=18586018 width=32)

 

​Its like ..

 

​NodeType (cost=startup-cost..total-cost rows=plan rows width=bytes per-row)

 

Documentation has briefed well on the explain output. Here's example.

 

 

Thanks  to all, but if this total cost is the total time it will take to retrieve the output then is it in minutes or milliseconds? If it’s in milliseconds does it mean that it take about 213 hrs for a total of 768375132.77

 

 

 

 

 

 

 

postgres=# explain select * from foo;

                        QUERY PLAN

-----------------------------------------------------------

 Seq Scan on foo  (cost=0.00..5770.01 rows=400001 width=4)

(1 row)

 

 

postgres=# EXPLAIN (FORMAT JSON) SELECT * FROM foo;

           QUERY PLAN

--------------------------------

 [                             +

   {                           +

     "Plan": {                 +

       "Node Type": "Seq Scan",+

       "Relation Name": "foo", +

       "Alias": "foo",         +

       "Startup Cost": 0.00,   +

       "Total Cost": 5770.01,  +

       "Plan Rows": 400001,    +

       "Plan Width": 4         +

     }                         +

   }                           +

 ]

(1 row)

 

 

---

Regards,

Raghavendra

EnterpriseDB Corporation

 

 

 

 

 

 

CONFIDENTIALITY NOTICE
The contents of and attachments to this e-mail are intended for the addressee only, and may contain the confidential
information of Argility (Proprietary) Limited and/or its subsidiaries. Any review, use or dissemination thereof by anyone
other than the intended addressee is prohibited.If you are not the intended addressee please notify the writer immediately
and destroy the e-mail. Argility (Proprietary) Limited and its subsidiaries distance themselves from and accept no liability
for unauthorised use of their e-mail facilities or e-mails sent other than strictly for business purposes.
 

 


CONFIDENTIALITY NOTICE
The contents of and attachments to this e-mail are intended for the addressee only, and may contain the confidential
information of Argility (Proprietary) Limited and/or its subsidiaries. Any review, use or dissemination thereof by anyone
other than the intended addressee is prohibited.If you are not the intended addressee please notify the writer immediately
and destroy the e-mail. Argility (Proprietary) Limited and its subsidiaries distance themselves from and accept no liability
for unauthorised use of their e-mail facilities or e-mails sent other than strictly for business purposes.

В списке pgsql-admin по дате отправления:

Предыдущее
От: Paul Dunkler
Дата:
Сообщение: Re: pg_xlog-files not deleted on a standby after accidental server crash
Следующее
От: Thomas Kellerer
Дата:
Сообщение: Re: Postgres 9 : - How to interpret the EXPLAIN query results