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Re: [PERFORM] Dataset is fetched from cache but still takes same timeto fetch records as first run - Mailing list pgsql-performance

From Sumeet Shukla
Subject Re: [PERFORM] Dataset is fetched from cache but still takes same timeto fetch records as first run
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Msg-id CABUL136B8cKAxqaBh_2bHZXCOhRs8jOrAQP99DQ9RnE7xweucA@mail.gmail.com
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In response to Re: [PERFORM] Dataset is fetched from cache but still takes same timeto fetch records as first run  (Dave Stibrany <dstibrany@gmail.com>)
Responses Re: [PERFORM] Dataset is fetched from cache but still takes same time to fetch records as first run
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Yes, but when I actually execute the query in pgAdmin3, it takes exactly the same time of 19.5 secs.
How is that possible?

Thanks & Regards,
Sumeet Shukla


On Thu, Jun 22, 2017 at 7:54 PM, Dave Stibrany <dstibrany@gmail.com> wrote:
The numbers you posted look exactly as I would expect. The first read hits disk and takes 108ms, the second read hits the cache and takes 27ms.

On Thu, Jun 22, 2017 at 8:40 PM, Sumeet Shukla <sumeet.k.shukla@gmail.com> wrote:
Both the first run and subsequent run takes same amount of time.

First Run:

"Seq Scan on d_payer (cost=0.00..8610.40 rows=121788 width=133) (actual time=8.760..98.582 rows=121788 loops=1)"
" Buffers: shared read=2521"
"Planning time: 16.820 ms"
"Execution time: 108.626 ms"


Second Run:

"Seq Scan on d_payer (cost=0.00..8610.40 rows=121788 width=133) (actual time=0.010..18.456 rows=121788 loops=1)"
" Buffers: shared hit=2521"
"Planning time: 0.083 ms"
"Execution time: 27.288 ms"


Can anyone please help me understand and fix this.


Thanks & Regards,
Sumeet Shukla



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