Mark Rostron <mrostron@ql2.com> writes:
> This message is a request for information about the "initplan" operation in explain plan.
An initplan is a sub-SELECT that only needs to be executed once because it
has no dependency on the immediately surrounding query level. The cases
you show here are from sub-SELECTs like this:
(select min(wu_id) from work_active limit 1)
which yields a value that's independent of anything in the outer query.
If there were an outer reference in there, you'd get a SubPlan instead,
because the subquery would need to be done over again for each row of
the outer query.
BTW, adding LIMIT 1 to an aggregate query is pretty pointless.
regards, tom lane
