Comment by netcraft

we do that by setting a local variable before the query and then reading that in the triggers:

```

  SET LOCAL foo.who_id = 'some-uuid';
  UPDATE table
  SET ...

```

```

  -- function to make getting the setting easier
  DROP FUNCTION IF EXISTS get_who_id (text);
  CREATE OR REPLACE FUNCTION get_who_id (default_value text DEFAULT null::text) RETURNS text AS $get_who_id$
 DECLARE
  who_id text;
 BEGIN
  BEGIN
   who_id := current_setting('foo.who_id');
  EXCEPTION
   WHEN SQLSTATE '42704' THEN
    RETURN default_value;
  END;
  IF (length(who_id) = 0) THEN
   RETURN default_value;
  END IF;
  return who_id;
 END
  $get_who_id$ LANGUAGE plpgsql VOLATILE;

```

```

  CREATE OR REPLACE FUNCTION some_table_audit () RETURNS   TRIGGER AS $some_table_audit$
 DECLARE
  who_id text;
 BEGIN

  who_id := get_who_id(null::text);
  ...

```

Identifiers changed, but hopefully will give you the idea.