Postgres Pro
Downloads
Home   >   mailing lists

Re: Postgres 9 : - How to interpret the EXPLAIN query results - Mailing list pgsql-admin

From Raghavendra
Subject Re: Postgres 9 : - How to interpret the EXPLAIN query results
Date
Msg-id CA+h6AhjktYYyGW2dEDctE5jR=z_5r=NKjrAF=XaSWZ6sosZaEw@mail.gmail.com
Whole thread Raw
In response to Postgres 9 : - How to interpret the EXPLAIN query results  (Khangelani Gama <kgama@argility.com>)
Responses Re: Postgres 9 : - How to interpret the EXPLAIN query results
List pgsql-admin
Tree view
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.

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)

http://www.postgresql.org/docs/9.3/static/sql-explain.html

---
Regards,
Raghavendra
EnterpriseDB Corporation
Blog: http://raghavt.blogspot.com/​

 

 

 

 

 

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.

pgsql-admin by date:

Previous
From: Anthony Nowocien
Date:
Subject: Re: Postgres 9 : - How to interpret the EXPLAIN query results
Next
From: Paul Dunkler
Date:
Subject: Re: pg_xlog-files not deleted on a standby after accidental server crash