dbListFields incorrectly returns columns which have been removed

[warnes]

Apparently postgresql doesn't actually remove 'dropped' columns, instead it renames them something like ........pg.dropped.23........, fills them with NULL and marks them as unused using the attisdroppped column of the pg_attribute table.

For example:

DROP TABLE IF EXISTS test_persons;

CREATE TABLE test_persons (
    PersonID int,
    LastName varchar(255),
    FirstName varchar(255),
    Address varchar(255),
    City varchar(255),
    State varchar(2),
    Dummy varchar(255)
);

INSERT INTO test_persons 
    (PersonID, LastName, FirstName, Address, City, State, Dummy)
VALUES
    (1, 'Sawyer', 'Tom',  'Apple Street', 'Riverside', 'MO', 'Dummy'),
    (2, 'Finn',   'Huck', 'Back Street', 'Riverside', 'MO', 'Dummy')
;    

ALTER TABLE test_persons
    DROP COLUMN Dummy;
    
SELECT
    a.attname,
    a.attisdropped
FROM
    pg_attribute a,
    pg_class c,
    pg_tables t,
    pg_namespace nsp
WHERE
    a.attrelid = c.oid
    AND c.relname = tablename
    AND c.relnamespace = nsp.oid
    AND a.attnum > 0
    AND nspname = CURRENT_SCHEMA()
    AND schemaname = nspname
    AND tablename = 'test_persons'
;

yeilds:

attname	attisdropped
personid	false
lastname	false
firstname	false
address	false
city	false
state	false
........pg.dropped.7........	true

and consequently

dbListFields(conn, 'test_persons')

yields

[1] "personid"                     "lastname"                    
[3] "firstname"                    "address"                     
[5] "city"                         "state"                       
[7] "........pg.dropped.7........"

Suggestion: Add an additional AND NOT a.attisdropped clause to the WHERE.