On Thu, July 26, 2018 at 1:25 AM, Michael Paquier wrote:
> Even if you have spiky workloads, sampling may miss those, but even with adding counters for each event
> you would need to query the table holding the counters at an insane frequency to be able to perhaps get
> something out of it as you need to do sampling of the counters as well to extract deltas.
Hi, I was wondering why PostgreSQL did not have the number of wait events and wait time that other databases such as
Oraclehad as a function, and when I was looking for related threads, I got to this thread.
I am a DB beginner, so please tell me. It says that you can find events that are bottlenecks in sampling, but as you
sawabove, you can not find events shorter than the sampling interval, right?
If this short event has occurred quite a number of times and it was a considerable amount of time in total, can you
solvethis problem with sampling?
# I have asked, but I could not understand much of the discussion above and I do not know if such a case can exist.
Also, I think that it can be solved by higher the sampling frequency, but the load will be high, right? I think this
methodis not very practical.
Moreover, I think that it is not implemented due to the reason that sampling is good as described above and because it
affectsperformance.
How about switching the function on / off and implementing with default off?
Do you care about performance degradation during bottleneck investigation?
When investigating the bottleneck, I think that it is better to find the cause even at the expense of performance.
# If you can detect with high frequency sampling, I think that it depends on whether the sampling or the function(the
numberof wait events and wait time) is high load.
Since I am a DB beginner, I think that it is saying strange things.
I am glad if you tell me.
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Naoki Yotsunaga
