From: Antonin Houska <ah@cybertec.at>
To: Corey Huinker <corey.huinker@gmail.com>
cc: Pavel Stehule <pavel.stehule@gmail.com>,
    PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Subject: Re: More efficient RI checks - take 2
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Comments: In-reply-to Corey Huinker <corey.huinker@gmail.com>
   message dated "Wed, 08 Apr 2020 13:55:55 -0400."
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Date: Mon, 20 Apr 2020 16:31:13 +0200
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Corey Huinker <corey.huinker@gmail.com> wrote:

> These numbers are very promising, and much more in line with my initial
> expectations. Obviously the impact on single-row DML is of major concern,
> though.

Yes, I agree.

> In doing my initial attempt, the feedback I was getting was that the people
> who truly understood the RI checks fell into the following groups:

> 1. people who wanted to remove the SPI calls from the triggers
> 2. people who wanted to completely refactor RI to not use triggers
> 3. people who wanted to completely refactor triggers
> 
> While #3 is clearly beyond the scope for an endeavor like this, #1 seems
> like it would nearly eliminate the 1-row penalty (we'd still have the
> TupleStore initi penalty, but it would just be a handy queue structure, and
> maybe that cost would be offset by removing the SPI overhead),

I can imagine removal of the SPI from the current implementation (and
constructing the plans "manually"), but note that the queries I use in my
patch are no longer that trivial. So the SPI makes sense to me because it
ensures regular query planning.

As for the tuplestore, I'm not sure the startup cost is a problem: if you're
concerned about the 1-row case, the row should usually be stored in memory.

> and once that is done, we could see about step #2.

As I said during my review of your patch last year, I think the RI semantics
has too much in common with that of triggers. I'd need more info to imagine
such a change.

-- 
Antonin Houska
Web: https://www.cybertec-postgresql.com