Most efficient way of bulk deleting rows from postgres

I'm wondering what the most efficient way would be to delete large numbers of rows from PostgreSQL, this process would be part of a recurring task every day to bulk import data (a delta of insertions + deletions) into a table. There could be thousands, potentially millions of rows to delete. I have a file of primary keys, one per line. The two options I was thinking of were along the lines of the below, but I don't know/understand enough of the internals of PostgreSQL to make an informed decision which would be best. - Execute a DELETE query for each row in the file, with a simple WHERE on primary key (or group the deletes in batches of n using an IN() clause) - Import the primary keys into a temporary table using the COPY command and then deleting from the main table using a join Any suggestions will be much appreciated!