How do I query INFORMATION_SCHEMA.COLUMNS on Amazon RDS?
PG_TABLE_DEF

Amazon considers the internal functions that INFORMATION_SCHEMA.COLUMNS is using Leader-Node Only functions. Rather than being sensible and redefining the standardized INFORMATION_SCHEMA.COLUMNS, Amazon sought to define their own proprietary version. For that they made available another function PG_TABLE_DEF which seems to address the same need. Pay attention to the note in the center about adding the schema to search_path.


  Stores information about table columns.
  
  PG_TABLE_DEF only returns information about tables that are visible to the user. If PG_TABLE_DEF does not return the expected results, verify that the search_path parameter is set correctly to include the relevant schemas.
  
  You can use SVV_TABLE_INFO to view more comprehensive information about a table, including data distribution skew, key distribution skew, table size, and statistics.


So using your example code (rewritten to use NOT EXISTS for clarity),

SET SEARCH_PATH to '$user', 'public', 'target_schema';

SELECT "column" 
FROM dev.fields f
WHERE NOT EXISTS (
  SELECT 1
  FROM PG_TABLE_DEF pgtd
  WHERE pgtd.column = f.field
  AND schemaname = 'target_schema'
);


See also,


Official docs on Querying Redshift System Tables