52.90. pg_stats_ext
The view
pg_stats_ext
provides access to
information about each extended statistics object in the database,
combining information stored in the
pg_statistic_ext
and
pg_statistic_ext_data
catalogs. This view allows access only to rows of
pg_statistic_ext
and
pg_statistic_ext_data
that correspond to tables the user owns, and therefore
it is safe to allow public read access to this view.
pg_stats_ext
is also designed to present the
information in a more readable format than the underlying catalogs
 at the cost that its schema must be extended whenever new types
of extended statistics are added to
pg_statistic_ext
.
Table 52.91.
pg_stats_ext
Columns
Column Type Description 

Name of schema containing table 
Name of table 
Name of schema containing extended statistics object 
Name of extended statistics object 
Owner of the extended statistics object 
Names of the columns included in the extended statistics object 
Expressions included in the extended statistics object 
Types of extended statistics object enabled for this record 
Ndistinct counts for combinations of column values. If greater
than zero, the estimated number of distinct values in the combination.
If less than zero, the negative of the number of distinct values divided
by the number of rows.
(The negated form is used when

Functional dependency statistics 
A list of the most common combinations of values in the columns. (Null if no combinations seem to be more common than any others.) 
A list of NULL flags for the most common combinations of values.
(Null when

A list of the frequencies of the most common combinations,
i.e., number of occurrences of each divided by total number of rows.
(Null when

A list of the base frequencies of the most common combinations,
i.e., product of pervalue frequencies.
(Null when

The maximum number of entries in the array fields can be controlled on a
columnbycolumn basis using the
ALTER
TABLE SET STATISTICS
command, or globally by setting the
default_statistics_target
runtime parameter.