Postgres Query Optimization: Left Join vs. Union All

I really wish this left join into union all optimization was applied automatically. There have been multiple discussions on the mailing list over the years, and no movement last I saw. It is such a performance cliff for the type of queries people expect to write when they hit an issue.

Having to decompose and rewrite as a union all manually, frankly sucks. I've got a number of these in my application and had to find each and every one by hitting a pathological data case where things started to fail.