pg_stats_ext
   The view pg_stats_ext provides access to
   the 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 has permission to read, 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 51.90. pg_stats_ext Columns
| Name | Type | References | Description | 
|---|---|---|---|
| schemaname | name |  | Name of schema containing table | 
| tablename | name |  | Name of table | 
| statistics_schemaname | name |  | Name of schema containing extended statistic | 
| statistics_name | name |  | Name of extended statistics | 
| statistics_owner | oid |  | Owner of the extended statistics | 
| attnames | name[] |  | Names of the columns the extended statistics is defined on | 
| kinds | text[] | Types of extended statistics enabled for this record | |
| n_distinct | pg_ndistinct | N-distinct 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 ANALYZEbelieves that
       the number of distinct values is likely to increase as the table grows;
       the positive form is used when the column seems to have a fixed number
       of possible values.)  For example, -1 indicates a unique combination of
       columns in which the number of distinct combinations is the same as the
       number of rows. | |
| dependencies | pg_dependencies | Functional dependency statistics | |
| most_common_vals | anyarray | A list of the most common combinations of values in the columns. (Null if no combinations seem to be more common than any others.) | |
| most_common_val_nulls | anyarray | A list of NULL flags for the most common combinations of values.
       (Null when most_common_valsis.) | |
| most_common_freqs | real[] | 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 most_common_valsis.) | |
| most_common_base_freqs | real[] | A list of the base frequencies of the most common combinations,
       i.e., product of per-value frequencies.
       (Null when most_common_valsis.) | 
   The maximum number of entries in the array fields can be controlled on a
   column-by-column basis using the ALTER TABLE SET STATISTICS
   command, or globally by setting the
   default_statistics_target run-time parameter.