9.30. Statistics Information Functions
Postgres Pro provides a function to inspect complex statistics defined using theCREATE 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-columnMCV list. It returns the following columns:
| Name | Type | Description |
|---|---|---|
index | integer | index of the item in theMCV list |
values | text[] | values stored in the MCV item |
nulls | boolean[] | flags identifyingNULL values |
frequency | double precision | frequency of thisMCV item |
base_frequency | double precision | base frequency of thisMCV item |
Thepg_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 thepg_mcv_list type can be obtained only from thepg_statistic_ext_data.stxdmcv column.