Source code for dagster_duckdb_pandas.duckdb_pandas_type_handler
from typing import Optional, Sequence, Type
import pandas as pd
from dagster import InputContext, MetadataValue, OutputContext, TableColumn, TableSchema
from dagster._core.storage.db_io_manager import DbTypeHandler, TableSlice
from dagster_duckdb.io_manager import (
DuckDbClient,
DuckDBIOManager,
build_duckdb_io_manager,
)
[docs]class DuckDBPandasTypeHandler(DbTypeHandler[pd.DataFrame]):
"""Stores and loads Pandas DataFrames in DuckDB.
To use this type handler, return it from the ``type_handlers` method of an I/O manager that inherits from ``DuckDBIOManager``.
Example:
.. code-block:: python
from dagster_duckdb import DuckDBIOManager
from dagster_duckdb_pandas import DuckDBPandasTypeHandler
class MyDuckDBIOManager(DuckDBIOManager):
@staticmethod
def type_handlers() -> Sequence[DbTypeHandler]:
return [DuckDBPandasTypeHandler()]
@asset(
key_prefix=["my_schema"] # will be used as the schema in duckdb
)
def my_table() -> pd.DataFrame: # the name of the asset will be the table name
...
defs = Definitions(
assets=[my_table],
resources={"io_manager": MyDuckDBIOManager(database="my_db.duckdb")}
)
"""
def handle_output(
self, context: OutputContext, table_slice: TableSlice, obj: pd.DataFrame, connection
):
"""Stores the pandas DataFrame in duckdb."""
connection.execute(
f"create table if not exists {table_slice.schema}.{table_slice.table} as select * from"
" obj;"
)
if not connection.fetchall():
# table was not created, therefore already exists. Insert the data
connection.execute(
f"insert into {table_slice.schema}.{table_slice.table} select * from obj"
)
context.add_output_metadata(
{
"row_count": obj.shape[0],
"dataframe_columns": MetadataValue.table_schema(
TableSchema(
columns=[
TableColumn(name=name, type=str(dtype)) # type: ignore # (bad stubs)
for name, dtype in obj.dtypes.items()
]
)
),
}
)
def load_input(
self, context: InputContext, table_slice: TableSlice, connection
) -> pd.DataFrame:
"""Loads the input as a Pandas DataFrame."""
if table_slice.partition_dimensions and len(context.asset_partition_keys) == 0:
return pd.DataFrame()
return connection.execute(DuckDbClient.get_select_statement(table_slice)).fetchdf()
@property
def supported_types(self):
return [pd.DataFrame]
duckdb_pandas_io_manager = build_duckdb_io_manager(
[DuckDBPandasTypeHandler()], default_load_type=pd.DataFrame
)
duckdb_pandas_io_manager.__doc__ = """
An I/O manager definition that reads inputs from and writes Pandas DataFrames to DuckDB. When
using the duckdb_pandas_io_manager, any inputs and outputs without type annotations will be loaded
as Pandas DataFrames.
Returns:
IOManagerDefinition
Examples:
.. code-block:: python
from dagster_duckdb_pandas import duckdb_pandas_io_manager
@asset(
key_prefix=["my_schema"] # will be used as the schema in DuckDB
)
def my_table() -> pd.DataFrame: # the name of the asset will be the table name
...
defs = Definitions(
assets=[my_table],
resources={"io_manager": duckdb_pandas_io_manager.configured({"database": "my_db.duckdb"})}
)
You can set a default schema to store the assets using the ``schema`` configuration value of the DuckDB I/O
Manager. This schema will be used if no other schema is specified directly on an asset or op.
.. code-block:: python
defs = Definitions(
assets=[my_table],
resources={"io_manager": duckdb_pandas_io_manager.configured({"database": "my_db.duckdb", "schema": "my_schema"})}
)
On individual assets, you an also specify the schema where they should be stored using metadata or
by adding a ``key_prefix`` to the asset key. If both ``key_prefix`` and metadata are defined, the metadata will
take precedence.
.. code-block:: python
@asset(
key_prefix=["my_schema"] # will be used as the schema in duckdb
)
def my_table() -> pd.DataFrame:
...
@asset(
metadata={"schema": "my_schema"} # will be used as the schema in duckdb
)
def my_other_table() -> pd.DataFrame:
...
For ops, the schema can be specified by including a "schema" entry in output metadata.
.. code-block:: python
@op(
out={"my_table": Out(metadata={"schema": "my_schema"})}
)
def make_my_table() -> pd.DataFrame:
...
If none of these is provided, the schema will default to "public".
To only use specific columns of a table as input to a downstream op or asset, add the metadata "columns" to the
In or AssetIn.
.. code-block:: python
@asset(
ins={"my_table": AssetIn("my_table", metadata={"columns": ["a"]})}
)
def my_table_a(my_table: pd.DataFrame) -> pd.DataFrame:
# my_table will just contain the data from column "a"
...
"""
[docs]class DuckDBPandasIOManager(DuckDBIOManager):
"""An I/O manager definition that reads inputs from and writes Pandas DataFrames to DuckDB. When
using the DuckDBPandasIOManager, any inputs and outputs without type annotations will be loaded
as Pandas DataFrames.
Returns:
IOManagerDefinition
Examples:
.. code-block:: python
from dagster_duckdb_pandas import DuckDBPandasIOManager
@asset(
key_prefix=["my_schema"] # will be used as the schema in DuckDB
)
def my_table() -> pd.DataFrame: # the name of the asset will be the table name
...
defs = Definitions(
assets=[my_table],
resources={"io_manager": DuckDBPandasIOManager(database="my_db.duckdb")}
)
You can set a default schema to store the assets using the ``schema`` configuration value of the DuckDB I/O
Manager. This schema will be used if no other schema is specified directly on an asset or op.
.. code-block:: python
defs = Definitions(
assets=[my_table],
resources={"io_manager": DuckDBPandasIOManager(database="my_db.duckdb", schema="my_schema")}
)
On individual assets, you an also specify the schema where they should be stored using metadata or
by adding a ``key_prefix`` to the asset key. If both ``key_prefix`` and metadata are defined, the metadata will
take precedence.
.. code-block:: python
@asset(
key_prefix=["my_schema"] # will be used as the schema in duckdb
)
def my_table() -> pd.DataFrame:
...
@asset(
metadata={"schema": "my_schema"} # will be used as the schema in duckdb
)
def my_other_table() -> pd.DataFrame:
...
For ops, the schema can be specified by including a "schema" entry in output metadata.
.. code-block:: python
@op(
out={"my_table": Out(metadata={"schema": "my_schema"})}
)
def make_my_table() -> pd.DataFrame:
...
If none of these is provided, the schema will default to "public".
To only use specific columns of a table as input to a downstream op or asset, add the metadata "columns" to the
In or AssetIn.
.. code-block:: python
@asset(
ins={"my_table": AssetIn("my_table", metadata={"columns": ["a"]})}
)
def my_table_a(my_table: pd.DataFrame) -> pd.DataFrame:
# my_table will just contain the data from column "a"
...
"""
@classmethod
def _is_dagster_maintained(cls) -> bool:
return True
@staticmethod
def type_handlers() -> Sequence[DbTypeHandler]:
return [DuckDBPandasTypeHandler()]
@staticmethod
def default_load_type() -> Optional[Type]:
return pd.DataFrame