PostgreSQL: count datasets / lines containing NULL values
You will need to use dynamic SQL to acheive this, perhaps like this:

testbed:

create role stack;
create schema authorization stack;
set role stack;

create table my_table as 
select generate_series(0,9) as id, null::integer as val;

create table my_table2 as 
select g as id, case when g&lt;=5 then null::integer else 1 end as val
from generate_series(0,9) g;


function:

create function get_with_nulls_rowcount(p_schema in text, p_table in text) 
                returns integer language plpgsql as $$
declare 
  n integer;
  s text;
begin
  --
  select array_to_string(array_agg(column_name::text||' is null'), ' or ')
  into s
  from information_schema.columns
  where table_schema=p_schema and table_name=p_table;
  --
  execute 'select count(*) from '||p_table||' where '||s into n;
  return n;
end;$$;


query:

select table_schema, table_name, 
       get_with_nulls_rowcount(table_schema, table_name)
from information_schema.tables
where table_schema='stack';


result:

 table_schema | table_name | get_with_nulls_rowcount
--------------+------------+-------------------------
 stack        | my_table   |                      10
 stack        | my_table2  |                       6
(2 rows)