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.
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