python - Hashed primary key -

i have table library each row represents music track. want make primary key track's audio fingerprint. unfortunately sqlalchemy passes me postgres error when try insert:

operationalerror: (psycopg2.operationalerror) index row size 3384 exceeds maximum 2712 index "library_fingerprint_key" hint:  values larger 1/3 of buffer page cannot indexed. consider function index of md5 hash of value, or use full text indexing.

i want store full fingerprint normal column , create hashed version primary key. i've tried using sqlalchemy's context-sensitive default functions still above error msg.

is there way automatically hash primary key based on column (the fingerprint column)?

code snippet below

def fingerprint_md5(context):         return hashlib.md5(context.current_parameters['fingerprint']).hexdigest()
  
class library(base):     tablename = 'library'     track_hash = column(string, primary_key=true, default=fingerprint_md5)     fingerprint = column(string, nullable=false, unique=true) 

updated index ddl:

indexes:     "library_pkey" primary key, btree (track_hash)     "library_fingerprint_key" unique constraint, btree (fingerprint)     "library_path_key" unique constraint, btree (path) 

the issue fingerprint value trying insert long index (primary key or otherwise). solution insert full fingerprint normal column no unique constraint, , calculate md5 hash primary key track_hash using code in op.