Re: BUG #14838: clock_timestamp() returns same values for each row

Jeff Janes <jeff(dot)janes(at)gmail(dot)com> writes:
> On Fri, Sep 29, 2017 at 6:43 AM, <zam6ak(at)gmail(dot)com> wrote:
>> We use clock_timestamp() function in our code and I have noticed that in PG
>> 10 RC1 it returns same values across rows...

> Probably not an issue of the different versions, but rather different
> compilers (or maybe different hardware?).

AFAICS, our code in this area (see src/port/gettimeofday.c) has not
changed since 9.5. I'm suspicious of a platform change.

> I get the same behavior on these two versions:
> ...
> and that behavior is that the timestamp jumps 500 usec at a time, despite
> looking as if it might have usec granularity:

What gettimeofday.c does is to use GetSystemTimePreciseAsFileTime()
if it can get hold of that, otherwise fall back to
GetSystemTimeAsFileTime(). I don't see anything very specific in
Windows' documentation about the resolution to be expected from either
one, but I wonder if the OP's 9.6 installation is using the former
while for some reason his 10rc1 installation is using the latter.

regards, tom lane