Re: [HACKERS] 64-bit queryId?

On 03/10/17 04:02, Joshua D. Drake wrote:
> On 10/01/2017 04:22 PM, Robert Haas wrote:
>> On Sun, Oct 1, 2017 at 3:48 PM, Greg Stark <stark@mit.edu> wrote:
>>> Well these kinds of monitoring systems tend to be used by operations
>>> people who are a lot more practical and a lot less worried about
>>> theoretical concerns like that.
>>
>> +1, well said.
>>
>>> In context the point was merely that the default
>>> pg_stat_statements.max of 5000 isn't sufficient to argue that 32-bit
>>> values are enough. It wouldn't be hard for there to be 64k different
>>> queries over time and across all the databases in a fleet and at that
>>> point it becomes likely there'll be a 32-bit collision.
>>
>> Yeah.
>>
>> I think Alexander Korotkov's points are quite good, too.
>>
>
> +1 to both of these as well.
>
> jD
>
Did a calculation:

#         probability of collision
54561        0.499993
54562        0.500005

Essentially, you hit a greater than 50% chance of a collision before you 
get to 55 thousand statements.


Cheers,
Gavin



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