17th September 2020: PostgreSQL 13 RC 1 Released!
Supported Versions: Current (12)
Development Versions: 13 / devel
This documentation is for an unsupported version of PostgreSQL.
You may want to view the same page for the current version, or one of the supported versions listed above instead.

9.30. Statistics Information Functions

PostgreSQL provides a function to inspect complex statistics defined using the CREATE STATISTICS command.

9.30.1. Inspecting MCV Lists

pg_mcv_list_items ( pg_mcv_list ) → setof record

pg_mcv_list_items returns a set of records describing all items stored in a multi-column MCV list. It returns the following columns:

Name Type Description
index integer index of the item in the MCV list
values text[] values stored in the MCV item
nulls boolean[] flags identifying NULL values
frequency double precision frequency of this MCV item
base_frequency double precision base frequency of this MCV item

The pg_mcv_list_items function can be used like this:

SELECT m.* FROM pg_statistic_ext join pg_statistic_ext_data on (oid = stxoid),
                pg_mcv_list_items(stxdmcv) m WHERE stxname = 'stts';

Values of the pg_mcv_list type can be obtained only from the pg_statistic_ext_data.stxdmcv column.