Information schema sql_identifier

Per version 12 release notes:

"Treat object-name columns in the information_schema views as being of 
type name, not varchar (Tom Lane)

Per the SQL standard, object-name columns in the information_schema 
views are declared as being of domain type sql_identifier. In 
PostgreSQL, the underlying catalog columns are really of type name. This 
change makes sql_identifier be a domain over name, rather than varchar 
as before. ..."

This came up in this SO question:

https://stackoverflow.com/questions/65416748/postgres-12-4-gives-function-does-not-exists-error

Where the query is:

SELECT (TABLE_SCHEMA || '"."' || TABLE_NAME) as table_name,
        pg_size_pretty(pg_table_size(table_name)) as table_size,
        pg_size_pretty(pg_indexes_size(table_name)) AS indexes_size,
        pg_size_pretty(pg_total_relation_size(table_name)) as total_size
from information_schema.TABLES nowait
where TABLE_SCHEMA='myschema'
order by pg_total_relation_size(table_name) desc;

And the error is:

"ERROR:  function pg_table_size(information_schema.sql_identifier) does 
not exist
LINE 1: ..."."' || TABLE_NAME) as table_name, pg_size_pretty(pg_table_s..."

My attempts:

SELECT pg_table_size(table_name)  from information_schema.tables;
ERROR:  function pg_table_size(information_schema.sql_identifier) does 
not exist
LINE 1: SELECT pg_table_size(table_name)  from information_schema.ta...

SELECT pg_table_size(table_name::text)  from information_schema.tables;
ERROR:  invalid name syntax

SELECT pg_table_size(table_name::regclass)  from information_schema.tables;
ERROR:  invalid name syntax

SELECT table_name::text::regclass  from information_schema.tables;
ERROR:  invalid name syntax

So how does one go about using a table name from 
information_schema.tables in pg_table_size()?


-- 
Adrian Klaver
adrian.klaver@aklaver.com