TypeError: unhashable type: 'list' error with the sqlalchemy insert query

Question

I am trying to insert a record into a oracle db via sqlalchemy, here is my below model:

class Item(Base):
    __tablename__ = 'items'
    id = db.Column(db.Integer, db.Sequence('item_id_seq'), nullable=False, primary_key=True)
    name = db.Column(db.String(128), nullable=True)

    def __init__(self, name):
        self.name = name

I have already created the table in the db by running the db migrate and upgrade. I am trying to insert a simple row in the db table as in :

test_obj = Item(name='item-1')
db.session.add(test_obj)
db.session.commit()

But the insert fails with the error TypeError: unhashable type: 'list'

But if I insert it along with the id (as below) and with the id initialized in the constructor, it inserts successfully.

test_obj = Item(id = 1, name='item-1')
db.session.add(test_obj)
db.session.commit()

class Item(Base):
    ...
    def __init__(self, id, name):
        self.id = id
        self.name = name

Since I have set id with a sequence, it should auto increment and get inserted automatically, but this is not the case here, any help would be appreciated.

This might be occuring due to this: github.com/sqlalchemy/sqlalchemy/issues/4335, I am trying to downgrade the version of cx-Oracle — Karan
– Karan, Commented Aug 27, 2019 at 22:43
I am using Oracle, I have updated the question, I had mentioned it in a flaw. — Karan
– Karan, Commented Aug 27, 2019 at 22:53

MastermindR · Accepted Answer · 2019-08-28 10:15:21Z

USE sqlalchemy 1.3.6 or above Sqlalchemy does not support auto increment for oracle 11g

if you are using "oracle 11g" then use following code:

from sqlalchemy import event
from sqlalchemy.schema import CreateSequence, DDL

db_session = sessionmaker(bind={your database engine})
class Item(Base):
    __tablename__ = 'items'
    id = db.Column(db.Integer, nullable=False, primary_key=True)
    name = db.Column(db.String(128), nullable=True)

    def __init__(self, name):
        self.name = name

def create_trigger_for_items(*args, **kwargs):
    with con.db_session() as session:
        session.execute(CreateSequence(db.Sequence('item_id_seq')))
        session.execute(DDL("""CREATE OR REPLACE TRIGGER ITEM_ID_TRIGGER 
                BEFORE INSERT ON items
                REFERENCING NEW AS NEW
                FOR EACH ROW 
                BEGIN
                :NEW.id := item_id_seq.NEXTVAL;
                END;"""))


event.listen(Item.__table__, "after_create",
             create_trigger_for_items)

if you are using "oracle 12" then use following code:

class Item(Base):
    __tablename__ = 'items'
    id = db.Column(db.Integer, db.Sequence('item_id_seq'), default=db.Sequence('item_id_seq').next_value(), primary_key=True)
    name = db.Column(db.String(128), nullable=True)

    def __init__(self, name):
        self.name = name

if you are using "oracle 12c" then use following code:

class Item(Base):
    __tablename__ = 'items'
    id = db.Column(db.Integer, autoincrement=True, primary_key=True)
    name = db.Column(db.String(128), nullable=True)

    def __init__(self, name):
        self.name = name

then you can use:

test_obj = Item(name='item-1')
db.session.add(test_obj)
db.session.commit()

noslenkwah · Accepted Answer · 2019-08-27 21:11:29Z

0

Just mark id as the primary_key.

class Item(Base):
    __tablename__ = 'items'
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(128), nullable=True)

def __init__(self, name):
    self.name = name

answered Aug 27, 2019 at 21:11

noslenkwah

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2 Comments

Karan Over a year ago

Thanks, I have tried this, but still doesn't work, I have updated the question along with the primary key field.

noslenkwah Over a year ago

It must be something outside of the code you've posted. Can you update your question with some more info? Maybe the complete stack trace.

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