vibhatha commented on code in PR #12590:
URL: https://github.com/apache/arrow/pull/12590#discussion_r842796789
##########
python/pyarrow/_compute.pyx:
##########
@@ -2182,3 +2255,175 @@ cdef CExpression _bind(Expression filter, Schema
schema) except *:
return GetResultValue(filter.unwrap().Bind(
deref(pyarrow_unwrap_schema(schema).get())))
+
+
+cdef CFunctionDoc _make_function_doc(func_doc):
+ """
+ Helper function to generate the FunctionDoc
+ """
+ cdef:
+ CFunctionDoc f_doc
+ vector[c_string] c_arg_names
+ c_bool c_options_required
+ if func_doc and isinstance(func_doc, dict):
+ if func_doc["summary"] and isinstance(func_doc["summary"], str):
+ f_doc.summary = func_doc["summary"].encode()
+ else:
+ raise ValueError("key `summary` cannot be None")
+
+ if func_doc["description"] and isinstance(func_doc["description"],
str):
+ f_doc.description = func_doc["description"].encode()
+ else:
+ raise ValueError("key `description` cannot be None")
+
+ if func_doc["arg_names"] and isinstance(func_doc["arg_names"], list):
+ for arg_name in func_doc["arg_names"]:
+ if isinstance(arg_name, str):
+ c_arg_names.push_back(arg_name.encode())
+ else:
+ raise ValueError(
+ "key `arg_names` must be a list of strings")
+ f_doc.arg_names = c_arg_names
+ else:
+ raise ValueError("key `arg_names` cannot be None")
+
+ # UDFOptions integration:
+ # TODO: https://issues.apache.org/jira/browse/ARROW-16041
+ f_doc.options_class = tobytes("None")
+
+ c_options_required = False
+ f_doc.options_required = c_options_required
+
+ return f_doc
+ else:
+ raise ValueError(f"func_doc must be a dictionary")
+
+
+def register_function(func_name, num_args, function_doc, in_types,
+ out_type, callback):
+ """
+ Register a user-defined-function
+
+ Parameters
+ ----------
+
+ func_name : str
+ function name
+ num_args : int
+ number of arguments in the function
+ function_doc : dict
+ a dictionary object with keys
+ ("summary",
+ "description",
+ "arg_names"
+ )
+ in_types : List[InputType]
+ list of InputType objects which defines the input
+ types for the function
+ out_type : DataType
+ output type of the function
+ callback : callable
+ user defined function
+ function includes arguments equal to the number
+ of input_types defined. The return type of the
+ function is of the type defined as output_type.
+ The output is a datum object which can be
+ an Array or a ChunkedArray or a Table or a RecordBatch.
+
+ Example
+ -------
+
+ >>> from pyarrow import compute as pc
+ >>> from pyarrow.compute import register_function
+ >>> from pyarrow.compute import InputType
+ >>>
+ >>> func_doc = {}
+ >>> func_doc["summary"] = "simple udf"
+ >>> func_doc["description"] = "add a constant to a scalar"
+ >>> func_doc["arg_names"] = ["x"]
+ >>>
+ >>> def add_constant(array):
+ ... return pc.call_function("add", [array, 1])
+ ...
+ >>>
+ >>> func_name = "py_add_func"
+ >>> arity = 1
+ >>> in_types = [InputType.array(pa.int64())]
+ >>> out_type = pa.int64()
+ >>> register_function(func_name, arity, func_doc,
+ ... in_types, out_type, add_constant)
+ >>>
+ >>> func = pc.get_function(func_name)
+ >>> func.name
+ 'py_add_func'
+ >>> ans = pc.call_function(func_name, [pa.array([20])])
+ >>> ans
+ <pyarrow.lib.Int64Array object at 0x10c22e700>
+ [
+ 21
+ ]
+ """
+ cdef:
+ c_string c_func_name
+ CArity c_arity
+ CFunctionDoc c_func_doc
+ CInputType in_tmp
+ vector[CInputType] c_in_types
+ PyObject* c_callback
+ shared_ptr[CDataType] c_type
+ COutputType* c_out_type
+ CScalarUdfBuilder* c_sc_builder
+ CStatus st
+ CScalarUdfOptions* c_options
+ object obj
+
+ if func_name and isinstance(func_name, str):
+ c_func_name = tobytes(func_name)
+ else:
+ raise ValueError("func_name should be str")
+
+ if num_args and isinstance(num_args, int):
+ assert num_args > 0
+ if num_args == 0:
+ c_arity = CArity.Nullary()
+ elif num_args == 1:
+ c_arity = CArity.Unary()
+ elif num_args == 2:
+ c_arity = CArity.Binary()
+ elif num_args == 3:
+ c_arity = CArity.Ternary()
+ elif num_args > 3:
+ c_arity = CArity.VarArgs(num_args)
Review Comment:
Good catch.
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