On Wed, Jan 17, 2018 at 7:56 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
Jacek Ko\xC5=82odziej <kolodziejj@gmail.com> writes: > Here's what happening to me: the "A" query occasionally (in my case: on the > order of tenths per day) returns an ID _higher_ than any ID present in > second query's result (other conditions I haven't specified do _not_ filter > any more rows than "id <= max ID") - as if some entries were visible for > the first query, but not for the second one. This is an inconsistency that > is very problematic for me.
That sounds problematic to me too, but how certain are you that the "other conditions you haven't specified" aren't suppressing the last row? That'd certainly be the least surprising explanation. If it isn't that, though, this surely seems like a bug.
Yes, I'm fairly sure of that. When I execute that same "B" query again some time afterwards, it returns all expected rows - I mean, also these that were "included" in original "A" query and that were "missing" in "B" one first time around.
Can you determine whether the row(s) missing in the second query are freshly committed? Or have they been there awhile?
Depends on what would be considered "fresh", usually it's on the order of miliseconds or seconds.
> Where am I wrong? What am I missing? What information may I provide to help > with investigating this?
Probably the best thing to spend time on would be to try to extract a publishable test case. It would be really hard to get to the bottom of an issue like this without having a reproducer. It's okay if it takes awhile to reproduce the fault ...
I'd certainly love to have a working repro. I won't be able to do it for the next few days but I'll work on this right after the weekend.
Also, before spending a whole lot of time on this: are you on 9.6.6? If not, update, just in case this is an already-fixed issue. The symptoms don't sound familiar, but I don't want to waste a lot of time only to find out it's some manifestation of a known bug.
regards, tom lane
I'm using 9.6.5; I'm not administrating it so it might take some time before updating but once it's done, I'll get back with whether that fixed the situation. In the meantime, when trying to reproduce it locally, I'll use both 9.6.5 and 9.6.6 to see whether it makes any difference.
