Dataset is fetched from cache but still takes same time to fetch records as first run

From: Sumeet Shukla <sumeet(dot)k(dot)shukla(at)gmail(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Subject: Dataset is fetched from cache but still takes same time to fetch records as first run
Date: 2017-06-23 00:40:35
Message-ID: CABUL137pc8pfW+KLm=7ucXpSDi_eG2qWiFMdR-3-UMEkZ=QUqA@mail.gmail.com
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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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