Nehil Jain
02/20/2024, 6:18 PMScout
02/20/2024, 6:18 PM__init__.py
to include the appropriate IO manager configuration for Postgres.
If a pre-built IO manager for Postgres is not available, you can create a custom IO manager by extending the ConfigurableIOManager
class and implementing the handle_output
and load_input
methods to interact with the Postgres database. This would involve writing custom logic to connect to the Postgres database, execute SQL queries, and handle the serialization and deserialization of data.
Here is a simplified example of how you might define a custom IO manager for Postgres, based on the example provided in the documentation for creating a custom IO manager:
python
from dagster import (
AssetKey,
OutputContext,
InputContext,
ConfigurableIOManager,
)
class MyPostgresIOManager(ConfigurableIOManager):
# ... initialization and configuration code for Postgres connection ...
def _get_path(self, asset_key: AssetKey) -> str:
# ... logic to determine the path or table name for the asset ...
def handle_output(self, context: OutputContext, obj):
# ... logic to write the data to the Postgres database ...
def load_input(self, context: InputContext):
# ... logic to read the data from the Postgres database ...
# ... Definitions and pipeline configuration using MyPostgresIOManager ...
Please note that this is a conceptual example, and the actual implementation would require more specific details about how to connect to and interact with the Postgres database. You would need to handle database connections, SQL query execution, and any necessary data serialization or deserialization.
For a complete and functional implementation, you would need to refer to the Dagster documentation, community examples, or potentially create a custom solution tailored to your specific requirements. Add alternative serialization formats fo... button Tutorial, part six: Using Dagster to sav... button Dagster Integrations Update | Dagster Bl... button I/O managers | Dagster button Thank you for your feedback!Nehil Jain
02/20/2024, 6:21 PMScout
02/20/2024, 6:21 PMPostgresIOManager
that you can use directly. However, I can guide you on how to create a custom IO manager for Postgres by extending the IOManager
class. The custom IO manager would need to implement methods for handling the output (handle_output
) and loading the input (load_input
). These methods would be responsible for writing to and reading from a Postgres database. Here's a conceptual outline of what such an implementation might look like: python import sqlalchemy from dagster import IOManager, OutputContext, InputContext class PostgresIOManager(IOManager): def __init__(self, engine): self.engine = engine def handle_output(self, context: OutputContext, obj): table_name = context.asset_key.path[-1] # Assuming 'obj' is a pandas DataFrame obj.to_sql(table_name, self.engine, if_exists='replace', index=False) def load_input(self, context: InputContext): table_name = context.upstream_output.asset_key.path[-1] with self.engine.connect() as conn: return pd.read_sql_table(table_name, conn) # Usage in a pipeline @io_manager def postgres_io_manager(init_context): engine = sqlalchemy.create_engine('<postgresql://username:password@host:port/dbname>') return PostgresIOManager(engine) @pipeline(mode_defs=[ModeDefinition(resource_defs={'io_manager': postgres_io_manager})]) def my_pipeline(): # define your pipeline here
In this example, the PostgresIOManager
class is initialized with a SQLAlchemy engine that connects to your Postgres database. The handle_output
method writes a pandas DataFrame to a table in the database, where the table name is derived from the asset key associated with the output. The load_input
method reads a table from the database into a pandas DataFrame, again using the asset key to determine the table name. Please note that this is a simplified example and does not include error handling, connection management, or other best practices for interacting with databases. You would need to expand upon this example to make it robust and suitable for production use. For a complete and functional implementation, you would need to refer to the Dagster documentation for guidance on creating custom IO managers, consult community examples, or potentially create a custom solution tailored to your specific requirements.Nehil Jain
02/20/2024, 6:28 PMScout
02/20/2024, 6:28 PMhandle_output
and load_input
calls to each of them. Here's a conceptual outline of how you might implement such a master IO manager:
python
from dagster import IOManager, OutputContext, InputContext, io_manager, ResourceDefinition
class MasterIOManager(IOManager):
def __init__(self, duckdb_io_manager, snowflake_io_manager, postgres_io_manager):
self.duckdb_io_manager = duckdb_io_manager
self.snowflake_io_manager = snowflake_io_manager
self.postgres_io_manager = postgres_io_manager
def handle_output(self, context: OutputContext, obj):
# Delegate to each IO manager
self.duckdb_io_manager.handle_output(context, obj)
self.snowflake_io_manager.handle_output(context, obj)
self.postgres_io_manager.handle_output(context, obj)
def load_input(self, context: InputContext):
# Example: load from DuckDB, but could be extended based on context or config
return self.duckdb_io_manager.load_input(context)
@io_manager(required_resource_keys={'duckdb_io_manager', 'snowflake_io_manager', 'postgres_io_manager'})
def master_io_manager(init_context):
return MasterIOManager(
init_context.resources.duckdb_io_manager,
init_context.resources.snowflake_io_manager,
init_context.resources.postgres_io_manager,
)
# Define your pipeline with the master IO manager and the other IO managers as resources
@pipeline(
mode_defs=[
ModeDefinition(
resource_defs={
'io_manager': master_io_manager,
'duckdb_io_manager': ResourceDefinition.hardcoded_resource(YourDuckDBIOManager()),
'snowflake_io_manager': ResourceDefinition.hardcoded_resource(YourSnowflakeIOManager()),
'postgres_io_manager': ResourceDefinition.hardcoded_resource(YourPostgresIOManager()),
}
)
]
)
def my_pipeline():
# define your pipeline here
In this example, MasterIOManager
takes three other IO managers as arguments and delegates the handle_output
method to each of them, effectively writing the output to three different storage systems. The load_input
method is an example of how you might load data from one of the storage systems, but you could extend this to be more dynamic based on the context or configScout
02/20/2024, 6:29 PMYourDuckDBIOManager
, YourSnowflakeIOManager
, or YourPostgresIOManager
. You would need to replace these placeholders with the actual IO manager instances for DuckDB, Snowflake, and Postgres. For a complete and functional implementation, you would need to refer to the Dagster documentation for guidance on creating custom IO managers, consult community examples, or potentially create a custom solution tailored to your specific requirements.