RE: How to always run UPDATE FROM despite missing records in the source table?

From: Alexander Farber <alexander(dot)farber(at)gmail(dot)com>

* The only workaround that I could think of is -

UPDATE users SET
visited = now(),
ip = '20.20.20.20'::inet,
lat = (SELECT lat FROM geoip WHERE '20.20.20.20'::inet <<= block),
lng = (SELECT lng FROM geoip WHERE '20.20.20.20'::inet <<= block)
WHERE uid = 2;

But that would run the same subquery twice (correct?) and my geoip table is already slow with 3073410 records (and that is why I am trying to cache its lat and lng values in the users table on each user login event)

Have you considered using a WITH clause to get the data so the query is only run once?
See section 7.8.2 at https://www.postgresql.org/docs/9.6/queries-with.html
Kevin
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