Re: accounting for memory used for BufFile during hash joins

From: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
To: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
Cc: Melanie Plageman <melanieplageman(at)gmail(dot)com>, Hubert Zhang <hzhang(at)pivotal(dot)io>, hackers <pgsql-hackers(at)postgresql(dot)org>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>
Subject: Re: accounting for memory used for BufFile during hash joins
Date: 2019-09-03 16:36:33
Message-ID: 20190903163633.GA16230@alvherre.pgsql
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On 2019-Jul-11, Tomas Vondra wrote:

> On Wed, Jul 10, 2019 at 04:51:02PM -0700, Melanie Plageman wrote:

> > I think implementing support for parallel hashjoin or explicitly
> > disabling it would be the bare minimum for this patch, which is why I
> > made 2 its own item. I've marked it as returned to author for this
> > reason.
>
> OK. I'm a bit confused / unsure what exactly our solution to the various
> hashjoin issues is. I have not been paying attention to all the various
> threads, but I thought we kinda pivoted to the BNL approach, no? I'm not
> against pushing this patch (the slicing one) forward and then maybe add
> BNL on top.

So what's a good way forward for this patch? Stalling forever like a
glacier is not an option; it'll probably end up melting. There's a lot
of discussion on this thread which I haven't read, and it's not
immediately clear to me whether this patch should just be thrown away in
favor of something completely different, or it can be considered a first
step in a long road.

--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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