On 05/31/2016 11:05 AM, Josh berkus wrote:
> On 05/31/2016 11:00 AM, Tom Lane wrote:
>> ! If this occurs, the plan will run with fewer workers than expected,
>> ! which may be inefficient. The default value is 2. Setting this
>> ! value to 0 disables parallel query execution.
>
> Is there a thread on how we determined this default of 2? I can't find
> one under likely search terms.
>
> I'm concerned about the effect of overallocating parallel workers on
> systems which are already running out of cores (e.g. AWS instances), and
> run with default settings. Possibly max_parallel_workers takes care of
> this, which is why I want to understand the logic here.
>
I don't remember the thread but I seem to recall that the default of 2
is explicitly during Beta, RC etc... so that we can see what happens.
Robert could speak better to that.
JD
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