optimizer statistics - cheeyoung/sqlplus-public GitHub Wiki

column group statistics (extended statistics)

• USER_STAT_EXTENSIONS view

column statistics

• histograms

Gathering

GATHER_OPTIMIZER_STATISTICS Hint
10.3.3 Online Statistics Gathering

14.1 Managing Column Group Statistics
14.2 Managing Expression Statistics
14 Managing Extended Statistics (21c)

DBMS_STATS enables you to collect extended statistics, which are statistics that can improve cardinality estimates when multiple predicates exist on different columns of a table, or when predicates use expressions.
An extension is either a column group or an expression. Column group statistics can improve cardinality estimates when multiple columns from the same table occur together in a SQL statement. Expression statistics improves optimizer estimates when predicates use expressions, for example, built-in or user-defined functions.