Re: Parallel Seq Scan - Mailing list pgsql-hackers

From Robert Haas
Subject Re: Parallel Seq Scan
Date
Msg-id CA+TgmoZtb3aBBoOX2rLBnTMWo1SLwsLp5hAPQkHapDEgHNzuBA@mail.gmail.com
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In response to Re: Parallel Seq Scan  (Amit Kapila <amit.kapila16@gmail.com>)
Responses Re: Parallel Seq Scan  (Amit Kapila <amit.kapila16@gmail.com>)
List pgsql-hackers
On Thu, Nov 12, 2015 at 10:39 PM, Amit Kapila <amit.kapila16@gmail.com> wrote:
> The number of shared buffers hit could be different across different runs
> because the read sequence of parallel workers can't be guaranteed, also
> I don't think same is even guaranteed for Seq Scan node,

The number of hits could be different.  However, it seems like any
sequential scan, parallel or not, should have a number of accesses
(hit + read) equal to the size of the relation.  Not sure if that's
what is happening here.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company



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