Re: Unexpected Performance for the Function simplify_function

>You're still admitting to nothing as to the hardware you are running
this test on.

I still do not get what you are saying. You want to know the disk is SSD or not?

It is HDD disk, AMD 3990X 64 Core CPU, 256GB RAM running Ubuntu 22.04

Best regards,

Jinsheng Ba

________________________________
From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Sent: Saturday, October 26, 2024 8:28 AM
To: Ba Jinsheng <bajinsheng(at)u(dot)nus(dot)edu>
Cc: pgsql-performance(at)lists(dot)postgresql(dot)org <pgsql-performance(at)lists(dot)postgresql(dot)org>
Subject: Re: Unexpected Performance for the Function simplify_function

- External Email -

Ba Jinsheng <bajinsheng(at)u(dot)nus(dot)edu> writes:
>> It looks like the better plan involves a
>> nestloop with inner indexscan on lineitem, which is something whose
>> estimated cost depends enormously on random_page_cost. You've given
>> us exactly zero detail about your test conditions, so it's hard to say
>> more than that.

> I used the default configuration in the file src/backend/utils/misc/postgresql.conf.sample
> So the random_page_cost = 4.0

You're still admitting to nothing as to the hardware you are running
this test on.

However, 4.0 is a number we chose decades ago based on typical
performance of spinning-rust storage. It's not very appropriate
for SSD or similar storage -- numbers just a bit above 1 are
probably the most appropriate thing for that kind of storage.
(There are ongoing discussions about changing the setting's default
value, but so far not backed by any great deal of hard evidence.)

regards, tom lane
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