SQLAlchemy error: An attempt to complete a transaction has failed. No corresponding transaction found

Question

I have installed:

Ubuntu (18.04)
Python (3.6.8)
msodbcsql17 (Microsoft ODBC Driver 17 for SQL Server)
SQLAlchemy (1.3.5)
Pandas (0.24.2)

and I want to create just a proof of concept using SQLAlchemy with an Azure SQL Data Warehouse. However, when I try to run a query on Customer model which is mapped to the customers view table using the code:

import urllib

from sqlalchemy import create_engine
from sqlalchemy import Column, Integer
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

db_username = 'username'
db_password = 'password'
db_database = 'dbname'
db_hostname = 'dbhost'
db_driver = 'ODBC Driver 17 for SQL Server'
db_port = '1433'

db_connectionString = f"DRIVER={{{db_driver}}}; SERVER={{{db_hostname}}}; DATABASE={{{db_database}}}; UID={{{db_username}}}; PWD={{{db_password}}}; PORT={{{db_port}}};"

engine_params = urllib.parse.quote_plus(db_connectionString)

engine = create_engine(f"mssql+pyodbc:///?odbc_connect={engine_params}", echo=True)

Base = declarative_base()

class Customer(Base):
    __tablename__ = 'customers'

    id = Column('Customer_ID', Integer, primary_key=True)

Session = sessionmaker(bind=engine)
session = Session()

customers_count = session.query(Customer).count()

session.close()

the following exception is thrown:

ProgrammingError: (pyodbc.ProgrammingError) ('42000', '[42000] [Microsoft][ODBC Driver 17 for SQL Server][SQL Server]111214;An attempt to complete a transaction has failed. No corresponding transaction found. (111214) (SQLEndTran)

Please, keep in mind that I can use the SQLAlchemy’s engine with pandas and run native SQL queries such:

data_frame = pandas.read_sql("SELECT COUNT(*) FROM customers", engine)

However, my need is to use the high-level query API of SQLAlchemy:

customers_count = session.query(Customer).count()

Any help would be really appreciated.

Asked By: Efstathios Chatzikyriakidis

||

Source

Answer 1

The SQLAlchemy documentation for mssql+pyodbc://… has just been updated to include the following (for SQLA 1.4/2.0):

Azure SQL Data Warehouse does not support transactions,
and that can cause problems with SQLAlchemy’s "autobegin" (and implicit
commit/rollback) behavior. We can avoid these problems by enabling autocommit
at both the pyodbc and engine levels:

connection_url = sa.engine.URL.create(
    "mssql+pyodbc",
    username="scott",
    password="tiger",
    host="dw.azure.example.com",
    database="mydb",
    query={
        "driver": "ODBC Driver 17 for SQL Server",
        "autocommit": "True",
    },
)
engine = create_engine(connection_url).execution_options(
    isolation_level="AUTOCOMMIT"
)

Answered By: Gord Thompson

Answer 2

To add to @Gord Thompson’s answer (apologies as I don’t have enough reputation to comment). For SQLAlchemy 1.4.32; if you only have admin rights for a schema and not the entire database, setting the transaction isolation level will throw an error when the library checks if the isolation level is valid against the database. To get around this I modified the code slightly.

connection_url = sa.engine.URL.create(
    "mssql+pyodbc",
    username="scott",
    password="tiger",
    host="dw.azure.example.com",
    database="mydb",
    query={
        "driver": "ODBC Driver 17 for SQL Server",
        "autocommit": "True",
    },
)
engine = create_engine(connection_url).execution_options()

This will give you a warning but does work.

Answered By: TheHappyEngineer

Answer 3

After many trials and errors, this worked for me:

engine = create_engine("mssql+pyodbc://username:password@server_name/database_name?"
                            "driver=ODBC+Driver+17+for+SQL+Server"
                            "&authentication=ActiveDirectoryPassword"
                            "&autocommit=True")

Answered By: Jakhon

SQLAlchemy error: An attempt to complete a transaction has failed. No corresponding transaction found

Question:

Answers: