On 2/1/16 6:13 PM, Andres Freund wrote:
I'm not sure what'd actually be a good upper limit. I'd be inclined to even go to as high as a week or so. A lot of our settings have upper/lower limits that aren't a good idea in general.
The only reason I can see for the 1 hour limit is to try and prevent footguns. I think that's a valid goal, but there should be a way to over-ride it. And if we don't want that kind of protection then I'd say just yank the upper limit.
I'm also wondering if it'd not make sense to raise the default timeout to 15min or so. The upper ceiling for that really is recovery time, and that has really shrunk rather drastically due to faster cpus and architectural improvements in postgres (bgwriter, separate checkpointer/bgwriter, restartpoints, ...).
It would be interesting if someone had a large-ish 9.4 or 9.5 install that they could test recovery timing on. My suspicion is that as long as FPWs are on that you'd generally end up limited by how fast you could read WAL unless you exceeded the FS cache. (I'm assuming a BBU and that the FS and controller will do a nice job of ordering writes optimally so that you'll get performance similar to reads when it's time to fsync.)
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