9.30. Statistics Information Functions
PostgreSQL provides a function to inspect complex statistics defined using the
CREATE STATISTICS command.pg_mcv_list_items returns a list of all items stored in a multi-column MCV list, and returns the following columns:Name | Type | Description |
|---|---|---|
index | int | 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 can be obtained only from the pg_statistic_ext_data.stxdmcv column.