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From: Bruce Momjian <bruce@momjian.us>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: aditya desai <admad123@gmail.com>
Cc: Justin Pryzby <pryzby@telsasoft.com>
Cc: Pgsql Performance <pgsql-performance@lists.postgresql.org>
Subject: Re: SELECT Query taking 200 ms on PostgreSQL compared to 4 ms on Oracle after migration.
Date: Sat, 3 Apr 2021 11:42:59 -0400
Message-ID: <20210403154259.GF29125@momjian.us> (raw)
In-Reply-To: <3972636.1617464359@sss.pgh.pa.us>
References: <CAN0SRDFV=Fv0zXHCGbh7gh=MTfw05Xd1x7gjJrZs5qn-TEphOw@mail.gmail.com>
	<CAFj8pRDycZjBLBaEkUcY4B01PS=ojoaBgQnzJaqBROTn8KM7Bg@mail.gmail.com>
	<20210403141651.GI6592@telsasoft.com>
	<CAN0SRDF6ZzxV-+OdgP6B+Zg0TmhrYFSOd3kK8GC5mkfo1icEGQ@mail.gmail.com>
	<20210403151201.GD29125@momjian.us>
	<3972636.1617464359@sss.pgh.pa.us>

On Sat, Apr  3, 2021 at 11:39:19AM -0400, Tom Lane wrote:
> Bruce Momjian <bruce@momjian.us> writes:
> > On Sat, Apr  3, 2021 at 08:38:18PM +0530, aditya desai wrote:
> >> Yes, force_parallel_mode is on. Should we set it off?
> 
> > Yes.  I bet someone set it without reading our docs:
> 
> > 	https://www.postgresql.org/docs/13/runtime-config-query.html#RUNTIME-CONFIG-QUERY-OTHER
> 
> > -->	Allows the use of parallel queries for testing purposes even in cases
> > -->	where no performance benefit is expected.
> 
> > We might need to clarify this sentence to be clearer it is _only_ for
> > testing.
> 
> I wonder why it is listed under planner options at all, and not under
> developer options.

I was kind of surprised by that myself since I was working on a blog
entry about from_collapse_limit and join_collapse_limit.  I think moving
it makes sense.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  If only the physical world exists, free will is an illusion.






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