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 52.28. 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 | 
| 
        If true, the stats include values from child tables, not just the values in the specified relation | 
| 
        
       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  | 
| 
        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 per-value frequencies.
       (Null when  | 
   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.