query's performance

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От	hmidi slim
Тема	query's performance
Дата	16 февраля 2018 г. 00:43:59
Msg-id	CAMsqVxu8Fme013y-5Zy7SwwBxMdmTJCu81Ym_YAKrFshw4kCUQ@mail.gmail.com обсуждение исходный текст
Ответы	Re: query's performance
Список	pgsql-general

Дерево обсуждения

Hi,
I have a table establishment which contains these columns: id, name, longitude, latitude.

I want to select all the establishments in the table establishment within a radius from a reference point which is a given establishment.

For example:

I have a given establishment called establishment1 and has an id=1.

I want to display all the establishments within a radius 1km from this establishment.

I wrote this query:

select e.name,e1.name, e1.longitude, e1.latitude

from establishment as e, establishment as e1

where e.id = 1

and e.id <> e1.id

and ST_DWithin(ST_SetSRID(ST_MakePoint(e1.longitude, e1.latitude), 4326),ST_MakePoint(e.longitude, e.latitude)::geography, 1000) ;

Is it a good practice to iterate the rows of the table like I did and does not have an effect in the performance if the number of table's rows increase?

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query's performance