Multivariate MCV list vs. statistics target

Hi,

One slightly inconvenient thing I realized while playing with the
address data set is that it's somewhat difficult to set the desired size
of the multi-column MCV list.

At the moment, we simply use the maximum statistic target for attributes
the MCV list is built on. But that does not allow keeping default size
for per-column stats, and only increase size of multi-column MCV lists.

So I'm thinking we should allow tweaking the statistics for extended
stats, and serialize it in the pg_statistic_ext catalog. Any opinions
why that would be a bad idea?

I suppose it should be part of the CREATE STATISTICS command, but I'm
not sure what'd be the best syntax. We might also have something more
similar to ALTER COLUMNT, but perhaps

ALTER STATISTICS s SET STATISTICS 1000;

looks a bit too weird.

regards

--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services