Re: JIT compiling with LLVM v12

From: Andres Freund <andres(at)anarazel(dot)de>
To: Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>
Cc: Noah Misch <noah(at)leadboat(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: JIT compiling with LLVM v12
Date: 2018-08-22 14:54:11
Message-ID: 20180822145411.7ggj65g5flufwrqs@alap3.anarazel.de
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Hi,

On 2018-08-22 16:36:00 +0200, Peter Eisentraut wrote:
> I'm suspicious that we haven't had much feedback about this. We've
> heard of one or two cases where LLVM broke a query outright, and that
> was fixed and that was a good result. But we haven't heard anything
> about performance regressions. Surely there must be some. There hasn't
> been any discussion or further analysis of the default cost settings
> either. I feel that we don't have enough information.

Yea. I don't think we'll get really good feedback before production
unfortunately :(

> I would like, however, that we make a decision one way or the other
> before the next beta. I've been handwaving a bit to users not to rely
> on the current betas for performance testing because the defaults might
> change later. That's bad either way.

I don't see particularly much benefit in deciding before beta,
personally. What's making you think it'd be important to decide before?
Pretty fundamentally, it'll be a setting you don't know is effectively
on, for the forseeable future anyway?

Greetings,

Andres Freund

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