On 2021-05-30 20:41, Christophe Pettus wrote:
On May 30, 2021, at 20:07, Dean Gibson (DB Administrator) <postgresql@mailpen.com> wrote: The first two JOINs are not the problem, & are in fact retained in my solution. The problem is the third JOIN, where "fips_county" from "County" is actually matched with the corresponding field from the "zip_code" VIEW. Works fine, if you don't mind the performance impact in v10 & above. It has now been rewritten, to be a sub-query for an output field. Voila ! Back to sub-second query times.
If, rather than a subquery, you explicitly called out the join criteria with ON, did it have the same performance benefit?
I thought that having a "USING" clause, was semantically equivalent to an "ON" clause with the equalities explicitly stated. So no, I didn't try that.
The matching that occurred is
exactly what I wanted. I just didn't want the performance impact.
