Got it, let's walk through how to pass the timeout parameter to pymssql when using SQLAlchemy with the mssql+pymssql:// connection string. There are a couple of straightforward ways to do this, depending on your preference:

1. Pass timeout via the connection URL query parameters #

You can append the timeout parameter directly to your connection string as a query argument. This maps straight to the timeout parameter in pymssql.connect() (units are seconds):

from sqlalchemy import create_engine

# Example with a 30-second connection timeout
engine = create_engine("mssql+pymssql://your_username:your_password@your_sql_server/your_database?timeout=30")

2. Pass timeout via connect_args in create_engine #

If you want to keep your connection string clean or need dynamic parameter handling, use the connect_args parameter of create_engine() to pass the timeout directly to the underlying pymssql.connect() call:

from sqlalchemy import create_engine

engine = create_engine(
    "mssql+pymssql://your_username:your_password@your_sql_server/your_database",
    connect_args={"timeout": 30}  # 30-second connection timeout
)

Critical Distinction: Connection Timeout vs. Query Execution Timeout #

Don't mix these two up—they serve different purposes:

• The timeout parameter we're passing to pymssql controls the connection timeout: how long the driver waits to establish a connection to the database server.
• If you need to limit how long a query runs, you'll use SQLAlchemy's execution_options for a query execution timeout:

For raw SQL queries:

with engine.connect() as conn:
    # Set a 30-second timeout for this specific query
    result = conn.execute("SELECT * FROM large_dataset", execution_options={"timeout": 30})

For ORM queries (using a Session):

from sqlalchemy.orm import sessionmaker

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

# Apply a 30-second execution timeout to an ORM query
query_result = session.query(YourModel).execution_options(timeout=30).all()

内容的提问来源于stack exchange，提问作者markfickett