On Wed, Jan 31, 2018 at 8:53 AM, Robert Haas <robertmh...@gmail.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
