Re: [External] RE: Estimate time without running the query

Em qui, 13 de set de 2018 às 19:53, David G. Johnston <
david(dot)g(dot)johnston(at)gmail(dot)com> escreveu:

> On Thu, Sep 13, 2018 at 3:30 PM, Neto pr <netoprbr9(at)gmail(dot)com> wrote:
>
>> The problem is that using the explain analyze <query> I have to wait for
>> the query to execute.
>> I would like to estimate the time without having to wait for the query
>> execution.
>> Does anyone know how to estimate the time without waiting for the query
>> to be executed?
>>
>
> On the machine in question you have to experiment to obtain data to
> construct a formula to convert cost to time. Then when using the function
> remember that lots of things can play into individual executions taking
> more time (and sometimes less too I suspect) such as locks, caching,
> physical data locality.
>
> It seems more useful to log actual execution times and look for trends.
> If you are writing a query odds are it needs to be run regardless of how
> efficient it may be - or used in a relative comparison to an alternate
> query.
>
>
Okay, David, but does not it have some SQL statement that returns a time
estimate, without having to execute the query?

> David J.
>
>