info
-----------------------------------------------------------------
  distribution: local
  vectorized: true

  • group (scalar)
  │
  └── • virtual table lookup join
      │ table: pg_class@pg_class_oid_idx
      │ equality: (attrelid) = (oid)
      │ pred: relname = 'b'
      │
      └── • virtual table lookup join (semi)
          │ table: pg_type@pg_type_oid_idx
          │ equality: (atttypid) = (oid)
          │ pred: typname = 'int8'
          │
          └── • filter
              │ filter: (NOT attnotnull) AND (attname = 'a_id')
              │
              └── • virtual table
                    table: pg_attribute@primary

-- setup
CREATE TABLE b (id INT, a_id INT);

root@localhost:26257/defaultdb> 
SELECT
  count(*)
FROM
  pg_class AS t INNER JOIN pg_attribute AS a ON t.oid = a.attrelid
WHERE
  a.attnotnull = 'f'
  AND a.attname = 'a_id'
  AND t.relname = 'b'
  AND a.atttypid
    IN (
        SELECT
          oid
        FROM
          pg_type
        WHERE
          typname = ANY (ARRAY['int8'])
      );
  count
---------
      0
(1 row)

root@localhost:26257/defaultdb> 
SELECT
  count(*)
FROM
  pg_class AS t
  INNER HASH JOIN pg_attribute AS a ON t.oid = a.attrelid
WHERE
  a.attnotnull = 'f'
  AND a.attname = 'a_id'
  AND t.relname = 'b'
  AND a.atttypid
    IN (
        SELECT
          oid
        FROM
          pg_type
        WHERE
          typname = ANY (ARRAY['int8'])
      );
  count
---------
      1
(1 row)