On Thu, Jun 20, 2019 at 08:08:44AM +0100, Dean Rasheed wrote:
On Tue, 18 Jun 2019 at 22:34, Tomas Vondra <tomas.von...@2ndquadrant.com> wrote:
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?
Seems reasonable to me. This might not be the only option we'll ever
want to add though, so perhaps a "stxoptions text[]" column along the
lines of a relation's reloptions would be the way to go.
I don't know - I kinda dislike the idea of stashing stuff like this into
text[] arrays unless there's a clear need for such flexibility (i.e.
vision to have more such options). Which I'm not sure is the case here.
And we kinda have a precedent in pg_attribute.attstattarget, so I'd use
the same approach here.
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.
Yes it does look a bit weird, but that's the natural generalisation of
what we have for per-column statistics, so it's probably preferable to
do that rather than invent some other syntax that wouldn't be so
consistent.
Yeah, I agree.
regards
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
