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# ask-ai
m

Marko Obert

03/08/2024, 3:21 PM
@Scout how to create a resource with pyodbc
s

Scout

03/08/2024, 3:21 PM
To create a resource with
pyodbc
in Dagster, you would typically define a Python class that inherits from
ConfigurableResource
. This class would establish a connection to your database using
pyodbc
and provide methods to interact with the database. Here's a step-by-step guide based on the documentation: 1. Define the Resource Class: Create a new Python class that inherits from
ConfigurableResource
. This class will encapsulate the logic for connecting to the database using
pyodbc
. 2. Configure the Resource: Define the configuration schema for your resource. This typically includes the database connection parameters such as the server, database name, username, password, and driver. 3. Implement Connection Methods: Implement methods to establish and close the database connection. You might also want to implement methods to execute queries or perform other database operations. 4. Use Context Managers: Optionally, you can use context managers to ensure that connections are properly closed after use. 5. Register the Resource: Add the resource to your Dagster repository so that it can be used by your assets or ops. Here is an example of how you might define a
pyodbc
resource in Dagster, based on the pattern shown in the documentation for creating resources:
Copy code
python
from dagster import ConfigurableResource, InitResourceContext
import pyodbc

class PyODBCResource(ConfigurableResource):
    server: str
    database: str
    username: str
    password: str
    driver: str

    def __init__(self, context: InitResourceContext):
        self.server = context.resource_config['server']
        self.database = context.resource_config['database']
        self.username = context.resource_config['username']
        self.password = context.resource_config['password']
        self.driver = context.resource_config['driver']

    def connect(self):
        connection_string = f"DRIVER={self.driver};SERVER={self.server};DATABASE={self.database};UID={self.username};PWD={self.password}"
        return pyodbc.connect(connection_string)

    def execute_query(self, query):
        with self.connect() as conn:
            cursor = conn.cursor()
            cursor.execute(query)
            return cursor.fetchall()

# Usage in an asset
@asset(required_resource_keys={"pyodbc_resource"})
def my_asset(context):
    query_result = context.resources.pyodbc_resource.execute_query("SELECT * FROM my_table")
    # Do something with query_result
In this example, the
PyODBCResource
class is a
ConfigurableResource
that uses
pyodbc
to connect to a database. The
connect
method creates a new connection using the provided configuration, and the
execute_query
method executes a given SQL query. Please note that this is a simplified example, a
nd in a real-world scenario, you would need to handle exceptions, manage transactions, and possibly implement additional methods for more complex database interactions. Additionally, you would need to add the resource to your Dagster repository's configuration to make it available to your assets or ops. Need help on how to create a MS SQL Serv... button Resources | Dagster button Python Class to Manage ELT in Multiple T... button Using Dagster with DuckDB | Dagster Docs button Thank you for your feedback!
m

Marko Obert

03/08/2024, 4:05 PM
Why is def __init__(self, context: InitResourceContext) needed?
@Scout Why is def __init__(self, context: InitResourceContext) needed?
s

Scout

03/08/2024, 4:09 PM
The
__init__
method with the
context: InitResourceContext
parameter is not strictly necessary when defining a resource in Dagster using the
ConfigurableResource
base class. My previous example was incorrect in that regard, and I apologize for the confusion. In Dagster, when you define a resource using the
@resource
decorator, you typically provide an initialization function that takes an
InitResourceContext
object. This context object contains all the information needed to initialize the resource, including configuration data and logging. Here's a corrected example of how you might define a
pyodbc
resource in Dagster:
Copy code
python
from dagster import resource, InitResourceContext
import pyodbc

@resource
def pyodbc_resource(init_context: InitResourceContext):
    server = init_context.resource_config['server']
    database = init_context.resource_config['database']
    username = init_context.resource_config['username']
    password = init_context.resource_config['password']
    driver = init_context.resource_config['driver']
    
    def connect():
        connection_string = f"DRIVER={driver};SERVER={server};DATABASE={database};UID={username};PWD={password}"
        return pyodbc.connect(connection_string)
    
    return connect

# Usage in an asset
@asset(required_resource_keys={"pyodbc_resource"})
def my_asset(context):
    connect = context.resources.pyodbc_resource
    with connect() as conn:
        cursor = conn.cursor()
        cursor.execute("SELECT * FROM my_table")
        query_result = cursor.fetchall()
    # Do something with query_result
In this example,
pyodbc_resource
is a function decorated with
@resource
that takes
InitResourceContext
as an argument. The function uses the configuration provided in the
InitResourceContext
to create a connection string and returns a
connect
function that establishes a connection to the database when called. The
InitResourceContext
is provided by Dagster during the execution of a pipeline and contains the configuration and other context needed to initialize the resource. It is a way for Dagster to pass runtime information to the resource at initialization time. Resources | Dagster button Dagster Docs button Allow to set default value for
EnvVar
button Nested resource dependencies do not work... button Thank you for your feedback!
m

Marko Obert

03/08/2024, 4:12 PM
@Scout But how would I formulate it as configurableresource
s

Scout

03/08/2024, 4:12 PM
In Dagster, if you want to define a resource as a
ConfigurableResource
, you would subclass
ConfigurableResource
and define the configuration schema using class attributes. The
ConfigurableResource
base class allows you to define resources with structured configuration in a more declarative way, using Python class syntax. Here's an example of how you might define a
pyodbc
resource as a `ConfigurableResource`:
Copy code
python from dagster import ConfigurableResource import pyodbc  class PyODBCResource(ConfigurableResource):     server: str     database: str     username: str     password: str     driver: str      def connect(self):         connection_string = f"DRIVER={self.driver};SERVER={self.server};DATABASE={self.database};UID={self.username};PWD={self.password}"         return pyodbc.connect(connection_string)  # Usage in an asset @asset(required_resource_keys={"pyodbc_resource"}) def my_asset(context):     connect = context.resources.pyodbc_resource.connect     with connect() as conn:         cursor = conn.cursor()         cursor.execute("SELECT * FROM my_table")         query_result = cursor.fetchall()     # Do something with query_result
In this example,
PyODBCResource
is a subclass of
ConfigurableResource
with class attributes that define the configuration schema. The
connect
method uses these attributes to create a connection string and establish a connection to the database. When you use this resource in an asset, you would provide the configuration for the resource in your Dagster repository definition, like so:
Copy code
python from dagster import asset, repository, define_asset_job  @repository def my_repository():     return [         my_asset,         define_asset_job('my_asset_job', selection=[my_asset]),         {             "resources": {                 "pyodbc_resource": PyODBCResource(                     server="my_server",                     database="my_database",                     username="my_username",                     password="my_password",                     driver="my_driver",                 )             }         }     ]
In this repository definition, you instantiate the
PyODBCResource
with the necessary configuration parameters. When the asset
my_asset
is executed, it will use the configured
pyodbc_resource
to connect to the database and perform the query.
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