Horton

Re: Parallel Seq Scan vs kernel read ahead

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Thomas Munro <thomas.munro@gmail.com>
Cc: David Rowley <dgrowleyml@gmail.com>, Ranier Vilela <ranier.vf@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2020-05-22T18:31:22Z
Lists: pgsql-hackers 
On Thu, May 21, 2020 at 6:28 PM Thomas Munro <thomas.munro@gmail.com> wrote:
> Right, I think it's safe.  I think you were probably right that
> ramp-up isn't actually useful though, it's only the end of the scan
> that requires special treatment so we don't get unfair allocation as
> the work runs out, due to course grain.

The ramp-up seems like it might be useful if the query involves a LIMIT.

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

Commits

  1. Allocate consecutive blocks during parallel seqscans