On 7 October 2017 at 2:49 PM, David Rowley wrote:
>
> Yeah, PostgreSQL does not make any effort to convert subqueries in the
> target list into joins. SQL server does.
[...]
> You'll probably find it'll run faster if you convert the subquery in
> the target list into a join with a GROUP BY, like ...
>
Wow, David, that is perfect – 0.91 seconds. Problem well and truly solved.
It took me a little while to modify my original query to use that concept, but now it flies.
Many thanks
Frank