"Edward Di Geronimo Jr." <edigeronimo@xtracards.com> writes:
> ... I'd like to know exactly what causes
> the bottleneck in the original query, and if there are other approaches
> to solving the issue in case I need them in future queries.
This is fairly hard to read ... it would help a lot if you had shown the
view definitions that the query relies on, so that we could match up the
plan elements with the query a bit better.
However, I'm thinking the problem is with this IN clause:
> where pl.network_id in (select ns.network_id
> from development.network_state ns
> where ns.from_date < current_time
> and (ns.thru_date > current_time or
> ns.thru_date is null)
> and (ns.state_cd = pl.state_cd or ns.state_cd='')
> )
Because the sub-SELECT references pl.state_cd (an outer variable
reference), there's no chance of optimizing this into a join-style IN.
So the sub-SELECT has to be re-executed for each row of the outer query.
BTW, it's not apparent to me that your "flattened" query gives the same
answers as the original. What if a pl row can join to more than one
row of the ns output?
regards, tom lane
