Understanding the explain statement

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От Benjamin Wragg
Тема Understanding the explain statement
Дата
Msg-id 000001c33132$3d9e82b0$0a00a8c0@mapping12
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Список pgsql-novice

Hi all,

 

Something I never have really understood is the explain statement. I know that it shows the query execution plan, but how am I meant to understand the output? For example could someone give me some pointers as to what is happening below?

 

Unique  (cost=10.25..10.47 rows=4 width=80)

  ->  Sort  (cost=10.25..10.25 rows=44 width=80)

        ->  Nested Loop  (cost=0.00..9.04 rows=44 width=80)

              ->  Index Scan using region_pkey on region  (cost=0.00..3.01 rows=1 width=32)

              ->  Index Scan using feature_the_geom_idx on feature  (cost=0.00..6.01 rows=1 width=48

)

 

Any pointers to some docs would be good.

 

Thanks,

 

Benjamin

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