snowflake.snowpark.functions.udaf¶

snowflake.snowpark.functions.udaf(handler: Optional[Type] = None, *, return_type: Optional[DataType] = None, input_types: Optional[List[DataType]] = None, name: Optional[Union[str, Iterable[str]]] = None, is_permanent: bool = False, stage_location: Optional[str] = None, imports: Optional[List[Union[str, Tuple[str, str]]]] = None, packages: Optional[List[Union[str, module]]] = None, replace: bool = False, if_not_exists: bool = False, session: Optional[Session] = None, parallel: int = 4, statement_params: Optional[Dict[str, str]] = None, immutable: bool = False, external_access_integrations: Optional[List[str]] = None, secrets: Optional[Dict[str, str]] = None, comment: Optional[str] = None, **kwargs) → Union[UserDefinedAggregateFunction, partial][source]¶

Registers a Python class as a Snowflake Python UDAF and returns the UDAF.

It can be used as either a function call or a decorator. In most cases you work with a single session. This function uses that session to register the UDAF. If you have multiple sessions, you need to explicitly specify the session parameter of this function. If you have a function and would like to register it to multiple databases, use session.udaf.register instead. See examples in UDAFRegistration.

Parameters:

• handler – A Python class used for creating the UDAF.

• return_type – A DataType representing the return data type of the UDAF. Optional if type hints are provided.

• input_types – A list of DataType representing the input data types of the UDAF. Optional if type hints are provided.

• name – A string or list of strings that specify the name or fully-qualified object identifier (database name, schema name, and function name) for the UDAF in Snowflake, which allows you to call this UDAF in a SQL command or via DataFrame.agg(). If it is not provided, a name will be automatically generated for the UDAF. A name must be specified when is_permanent is True.

• is_permanent – Whether to create a permanent UDAF. The default is False. If it is True, a valid stage_location must be provided.

• stage_location – The stage location where the Python file for the UDAF and its dependencies should be uploaded. The stage location must be specified when is_permanent is True, and it will be ignored when is_permanent is False. It can be any stage other than temporary stages and external stages.

• imports – A list of imports that only apply to this UDAF. You can use a string to represent a file path (similar to the path argument in add_import()) in this list, or a tuple of two strings to represent a file path and an import path (similar to the import_path argument in add_import()). These UDAF-level imports will override the session-level imports added by add_import(). Note that an empty list means no import for this UDAF, and None or not specifying this parameter means using session-level imports.

• packages – A list of packages that only apply to this UDAF. These UDAF-level packages will override the session-level packages added by add_packages() and add_requirements(). Note that an empty list means no package for this UDAF, and None or not specifying this parameter means using session-level packages. To use Python packages that are not available in Snowflake, refer to custom_package_usage_config().

• replace – Whether to replace a UDAF that already was registered. The default is False. If it is False, attempting to register a UDAF with a name that already exists results in a SnowparkSQLException exception being thrown. If it is True, an existing UDAF with the same name is overwritten.

• if_not_exists – Whether to skip creation of a UDAF when one with the same signature already exists. The default is False. if_not_exists and replace are mutually exclusive and a ValueError is raised when both are set. If it is True and a UDAF with the same signature exists, the UDAF creation is skipped.

• session – Use this session to register the UDAF. If it’s not specified, the session that you created before calling this function will be used. You need to specify this parameter if you have created multiple sessions before calling this method.

• parallel – The number of threads to use for uploading UDAF files with the PUT command. The default value is 4 and supported values are from 1 to 99. Increasing the number of threads can improve performance when uploading large UDAF files.

• statement_params – Dictionary of statement level parameters to be set while executing this action.

• immutable – Whether the UDAF result is deterministic or not for the same input.

• external_access_integrations – The names of one or more external access integrations. Each integration you specify allows access to the external network locations and secrets the integration specifies.

• secrets – The key-value pairs of string types of secrets used to authenticate the external network location. The secrets can be accessed from handler code. The secrets specified as values must also be specified in the external access integration and the keys are strings used to retrieve the secrets using secret API.

• comment – Adds a comment for the created object object. See COMMENT

Returns:

A UDAF function that can be called with Column expressions.

Note

1. When type hints are provided and are complete for a function, return_type and input_types are optional and will be ignored. See details of supported data types for UDAFs in UDAFRegistration.

• You can use use Variant to annotate a variant, and use Geography to annotate a geography when defining a UDAF.

• typing.Union is not a valid type annotation for UDAFs, but typing.Optional can be used to indicate the optional type.

• Type hints are not supported on functions decorated with decorators.

2. A temporary UDAF (when is_permanent is False) is scoped to this session and all UDAF related files will be uploaded to a temporary session stage (session.get_session_stage()). For a permanent UDAF, these files will be uploaded to the stage that you provide.

3. By default, UDAF registration fails if a function with the same name is already registered. Invoking udaf() with replace set to True will overwrite the previously registered function.

See also

UDAFRegistration

Example::

>>> from snowflake.snowpark.types import IntegerType
>>> class PythonSumUDAF:
...     def __init__(self) -> None:
...         self._sum = 0
...
...     @property
...     def aggregate_state(self):
...         return self._sum
...
...     def accumulate(self, input_value):
...         self._sum += input_value
...
...     def merge(self, other_sum):
...         self._sum += other_sum
...
...     def finish(self):
...         return self._sum
>>> sum_udaf = udaf(
...     PythonSumUDAF,
...     name="sum_int",
...     replace=True,
...     return_type=IntegerType(),
...     input_types=[IntegerType()],
... )
>>> df = session.create_dataframe([[1, 3], [1, 4], [2, 5], [2, 6]]).to_df("a", "b")
>>> df.agg(sum_udaf("a")).collect()
[Row(SUM_INT("A")=6)]

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Instead of calling udaf it is also possible to use udaf as a decorator.

Example:

>>> @udaf(name="sum_int", replace=True, return_type=IntegerType(), input_types=[IntegerType()])
... class PythonSumUDAF:
...     def __init__(self) -> None:
...         self._sum = 0
...
...     @property
...     def aggregate_state(self):
...         return self._sum
...
...     def accumulate(self, input_value):
...         self._sum += input_value
...
...     def merge(self, other_sum):
...         self._sum += other_sum
...
...     def finish(self):
...         return self._sum

>>> df = session.create_dataframe([[1, 3], [1, 4], [2, 5], [2, 6]]).to_df("a", "b")
>>> df.agg(PythonSumUDAF("a")).collect()
[Row(SUM_INT("A")=6)]

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