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

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От Raghavendra
Тема Re: Postgres 9 : - How to interpret the EXPLAIN query results
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Msg-id CA+h6AhjktYYyGW2dEDctE5jR=z_5r=NKjrAF=XaSWZ6sosZaEw@mail.gmail.com
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Ответ на Postgres 9 : - How to interpret the EXPLAIN query results  (Khangelani Gama <kgama@argility.com>)
Ответы Re: Postgres 9 : - How to interpret the EXPLAIN query results
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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/​

 

 

 

 

 

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