[SOLVED] cast column to bytea type in postgresql for pgm_sym

cast column to bytea type in postgresql for pgm_sym_decrypt in sqlalchemy

I'm very new to fastapi and python altogether. I'm using pgcrypto module to encrypt the personal info of the customers. My raw query is

select pgp_sym_decrypt(cast(email as bytea), 'secret_key') as email
from customers

and the query works fine. How to produce something similar in SqlAlchemy? I've tried something like this

from sqlalchemy import select, func, cast, LargeBinary
from sqlalchemy.dialects.postgresql import BYTEA

customer = select(func.pgp_sym_decrypt(cast(Customer.c.email, 'bytea'), 'secret_key'))

Also tried

customer = select(func.pgp_sym_decrypt(cast(Customer.c.email, BYTEA), 'secret_key'))

Also tried

customer = select(func.pgp_sym_decrypt(cast(Customer.c.email, LargeBinary), 'secret_key'))

But no luck anywhere. So, how to solve this problem? Any help would be appreciated. Thank you so much in advance.

Solution

The pgp_sym_decypt function takes a BYTEA as its argument, but pgp_sym_encrypt takes a VARCHAR, so casting is unnecessary.

import sqlalchemy as sa

engine = sa.create_engine('postgresql+psycopg2:///test', echo=True, future=True)

tbl = sa.Table('t70770085', sa.MetaData(),
               sa.Column('id', sa.Integer, primary_key=True),
               sa.Column('name', sa.String))
tbl.drop(engine, checkfirst=True)
tbl.create(engine)

SECRET = 'secret_key'

with engine.begin() as conn:
    conn.execute(tbl.insert().values(name=sa.func.pgp_sym_encrypt('Alice', SECRET)))

with engine.connect() as conn:
    query = sa.select(sa.func.pgp_sym_decrypt(sa.cast(tbl.c.name, sa.LargeBinary), SECRET))
    result = conn.execute(query)
    print(result.scalar_one())