Re: JIT compiling with LLVM v9.0

On Wed, Jan 31, 2018 at 8:53 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> As far as the second one, looking back at what happened with parallel
> query, I found (on a quick read) 13 back-patched commits in
> REL9_6_STABLE prior to the release of 10.0, 3 of which I would qualify
> as low-importance (improving documentation, fixing something that's
> not really a bug, improving a test case). A couple of those were
> really stupid mistakes on my part. On the other hand, would it have
> been overall worse for our users if that feature had been turned on in
> 9.6? I don't know. They would have had those bugs (at least until we
> fixed them) but they would have had parallel query, too. It's hard
> for me to judge whether that was a win or a loss, and so here. Like
> parallel query, this is a feature which seems to have a low risk of
> data corruption, but a fairly high risk of wrong answers to queries
> and/or strange errors. Users don't like that. On the other hand,
> also like parallel query, if you've got the right kind of queries, it
> can make them go a lot faster. Users DO like that.

As a data point, I can tell you that Heroku enabled parallel query for
9.6 immediately, and it turned out fine. The first version available
as stable was probably 9.6.3 -- there or thereabouts.

There were some bugs, of course, but not to the extent that 9.6 was
looked upon as being more buggy than the average Postgres release.

--
Peter Geoghegan