ERROR: duplicate key value

PB being out of action, making playlists and doing Telugu database work etc. So, while importing Telugu files, came across

ERROR: duplicate key value violates unique constraint "download_filename_file_id_ukey"

This causes some files not to be entered into database, so when importing playlist, it complains that some fids are NULL

Solution was to import files one by one till the offending file was found - a file which had the same name as an existing file, but with space in the filename replaced with underscore. Removed the old entry from database - rather, changed space to underscore for its filename.