In many ways there's not a lot to choose between them. (You can find
examples where the optimizer "misbehaves" wrong in either case.)
As a general principle, though, I prefer to keep the "extended stats"
method available for "column group" statistics and use virtual columns for
user-visible expressions.
In passing, I wouldn't use "for all columns skewonly" and generally I'd
avoid skewonly (or anything else that allowed the code to decide whether or
not to create a histogram).
Regards
Jonathan Lewis
On Thu, 18 Mar 2021 at 15:09, mcpeakm@xxxxxxxxxxxxxxxxxxxxxxxxxxx <
mcpeakm@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
Jonathan,
Is creating a virtual column and then gathering a histogram on that
different/better than gathering expression statistics via something like:
BEGIN
DBMS_STATS.GATHER_TABLE_STATS(user, 'ORDERS', method_opt => 'FOR ALL
COLUMNS SIZE SKEWONLY FOR COLUMNS ( order_processing_date -
business_processing_date) SIZE SKEWONLY');
END;
?
