51.89. 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

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
ANALYZE
believes 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_vals
is.)


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_vals
is.)


most_common_base_freqs

real[]

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

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.