Check the column size in PostgreSQL

https://stackoverflow.com/questions/18316893/how-to-estimate-the-size-of-one-column-in-a-postgres-table

SELECT
    pg_size_pretty(sum(pg_column_size(컬럼이름))) as total_size,
    pg_size_pretty(avg(pg_column_size(컬럼이름))) as average_size
FROM 테이블이름;