Re: [GENERAL] Question regarding the output of postgresql *explain* command

[Arup Rakshit]

Hi Tom,

Thanks, I’ll read this page.




> On May 28, 2017, at 8:36 PM, Tom Lane  wrote:
> 
> Arup Rakshit  writes:
>> I was reading to day how indexing works. And I was trying some query, for 
>> example below one. What the range basically means (cost=0.28..8.30 ? I don’t 
>> understand this.
> 
> https://www.postgresql.org/docs/current/static/using-explain.html
> 
>   regards, tom lane


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Re: [GENERAL] Question regarding the output of postgresql *explain* command

[Tom Lane]

Arup Rakshit  writes:
> I was reading to day how indexing works. And I was trying some query, for 
> example below one. What the range basically means (cost=0.28..8.30 ? I don’t 
> understand this.

https://www.postgresql.org/docs/current/static/using-explain.html

regards, tom lane


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[GENERAL] Question regarding the output of postgresql *explain* command

[Arup Rakshit]

Hi,


I was reading to day how indexing works. And I was trying some query, for 
example below one. What the range basically means (cost=0.28..8.30 ? I don’t 
understand this.


———


arup@ror ~/part-time-projects/entrylvl (add_index_to_job_sources)$ rails db
psql (9.5.0)
Type "help" for help.

entrylvl_dev=# \d job_sources;
   Table "public.job_sources"
Column |Type |Modifiers
---+-+--
 id| bigint  | not null default 
nextval('job_sources_id_seq'::regclass)
 job_id| bigint  |
 source| character varying   |
 job_source_id | character varying   |
 created_at| timestamp without time zone | not null
 updated_at| timestamp without time zone | not null
Indexes:
"job_sources_pkey" PRIMARY KEY, btree (id)
"index_job_sources_on_source_and_job_source_id" UNIQUE, btree (source, 
job_source_id)
"index_job_sources_on_job_id" btree (job_id)
Foreign-key constraints:
"fk_rails_f45da00eca" FOREIGN KEY (job_id) REFERENCES jobs(id)

entrylvl_dev=# explain select * from job_sources where job_source_id = 
'p_1208b146c9eb8905' AND source = 'indeed';
QUERY PLAN
--
 Index Scan using index_job_sources_on_source_and_job_source_id on job_sources  
(cost=0.28..8.30 rows=1 width=58)
   Index Cond: (((source)::text = 'indeed'::text) AND ((job_source_id)::text = 
'p_1208b146c9eb8905'::text))
(2 rows)

entrylvl_dev=#

—


Thanks,
Arup