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: Ranier Vilela <ranier.vf@gmail.com>
Cc: David Rowley <dgrowleyml@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Thomas Munro <thomas.munro@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2020-06-22T19:32:59Z
Lists: pgsql-hackers 
Ranier,

This topic is largely unrelated to the current thread. Also...

On Mon, Jun 22, 2020 at 12:47 PM Ranier Vilela <ranier.vf@gmail.com> wrote:
> Questions:
> 1. Why acquire and release lock in retry: loop.

This is a super-bad idea. Note the coding rule mentioned in spin.h.
There are many discussion on this mailing list about the importance of
keeping the critical section for a spinlock to a few instructions.
Calling another function that *itself acquires an LWLock* is
definitely not OK.

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

Commits

  1. Allocate consecutive blocks during parallel seqscans