Delete 1 Record of 2 Duplicate Records - Mailing list pgsql-sql

How do I delete only 1 of the duplicate records?

column_name | column_id
---------------------+--------------test1                 |         5test1                 |         5


I've tried this:

tmp_test=# delete from test where column_id = 5 limit 1;
ERROR:  parser: parse error at or near "limit"

I'm using version 7.2.1

Thank you.