Snowflake SQLAlchemy Dialect

Warnings

• breaking The default behavior of the division operator (`/`) in SnowflakeDialect changed in version 1.7.3. Previously, `/` was integer division; it is now float division, aligning with standard Python 3 behavior. Integer division is now `//`. A `force_div_is_floordiv` flag was added for backward compatibility, but it is slated for removal in future releases.
  Fix: Review code using division (`/`) and explicitly use `//` for integer division or `force_div_is_floordiv=True` in connection parameters, understanding it's a temporary workaround.
• gotcha Snowflake stores all case-insensitive object names (e.g., table, column names) in uppercase. SQLAlchemy, by default, considers lowercase object names as case-insensitive. This mismatch can lead to issues during schema reflection (e.g., `get_table_names`, `get_columns`) if object names are not consistently handled (e.g., quoted identifiers for case-sensitivity).
  Fix: Use consistent casing for object names in your SQLAlchemy models and queries. For case-sensitive identifiers, ensure they are properly quoted by SQLAlchemy or Snowflake. When reflecting, be aware of how SQLAlchemy handles returned names.
• gotcha It is critical to explicitly close connections (`connection.close()`) before disposing of the engine (`engine.dispose()`). Failing to do so can prevent the underlying Snowflake Connector for Python from properly closing sessions, leading to resource leaks or unexpected behavior.
  Fix: Always use `with engine.connect() as connection:` for managing connections or explicitly call `connection.close()` and `engine.dispose()` in a `finally` block to ensure proper resource cleanup.
• breaking Compatibility with `snowflake-connector-python` versions. For example, version 1.8.0 bumped the required `snowflake-connector-python` to be less than 5.0.0, and `v1.8.1` was yanked due to connector compatibility. Ensure your connector version is within the supported range for your `snowflake-sqlalchemy` version.
  Fix: Check the `snowflake-sqlalchemy` release notes or `setup.py` for specific `snowflake-connector-python` version constraints and install a compatible version using `pip install "snowflake-connector-python<X.Y.Z"` if necessary.
• gotcha Special characters like '%' or '@' in passwords or other connection parameters within a URL connection string must be URL-encoded to be parsed correctly by SQLAlchemy and the underlying connector.
  Fix: Use `urllib.parse.quote_plus()` or `urllib.parse.quote()` to encode special characters in connection string components, especially passwords.
• gotcha Schema reflection could cause crashes in version 1.9.0 when reflecting without specifying a schema, due to `None` arguments in internal schema resolution, or when `SHOW TABLES` returns unexpected results.
  Fix: Upgrade to a version beyond 1.9.0 if available, or explicitly specify the schema when performing reflection operations (`inspector.get_table_names(schema='your_schema')`).

Install

• pip install snowflake-sqlalchemy Install latest version

Imports

• create_engine

  from sqlalchemy import create_engine

• URL

  from snowflake.sqlalchemy import URL

  The Snowflake-specific URL constructor is part of the snowflake.sqlalchemy module, not directly from SQLAlchemy's base URL module.

Quickstart

This quickstart demonstrates how to establish a connection to Snowflake using `create_engine` with the `snowflake.sqlalchemy.URL` object. It then executes a simple query to retrieve the current Snowflake version. Remember to replace placeholder credentials with your actual Snowflake account details or set them as environment variables. It's crucial to properly close the connection and dispose of the engine.

import os
from sqlalchemy import create_engine, text
from snowflake.sqlalchemy import URL

# Replace with your Snowflake credentials or set them as environment variables
SNOWFLAKE_ACCOUNT = os.environ.get('SNOWFLAKE_ACCOUNT', 'your_account_identifier')
SNOWFLAKE_USER = os.environ.get('SNOWFLAKE_USER', 'your_user_login_name')
SNOWFLAKE_PASSWORD = os.environ.get('SNOWFLAKE_PASSWORD', 'your_password')
SNOWFLAKE_WAREHOUSE = os.environ.get('SNOWFLAKE_WAREHOUSE', 'your_warehouse')
SNOWFLAKE_DATABASE = os.environ.get('SNOWFLAKE_DATABASE', 'your_database')
SNOWFLAKE_SCHEMA = os.environ.get('SNOWFLAKE_SCHEMA', 'your_schema')

try:
    engine = create_engine(
        URL(
            account=SNOWFLAKE_ACCOUNT,
            user=SNOWFLAKE_USER,
            password=SNOWFLAKE_PASSWORD,
            database=SNOWFLAKE_DATABASE,
            schema=SNOWFLAKE_SCHEMA,
            warehouse=SNOWFLAKE_WAREHOUSE
        )
    )

    with engine.connect() as connection:
        result = connection.execute(text('SELECT current_version()')).fetchone()
        print(f"Connected to Snowflake. Current version: {result[0]}")

except Exception as e:
    print(f"Error connecting to Snowflake: {e}")
finally:
    if 'engine' in locals():
        engine.dispose() # Ensures all connections are closed.