Github user jkbradley commented on a diff in the pull request:
https://github.com/apache/spark/pull/18746#discussion_r131223795
--- Diff: python/pyspark/ml/base.py ---
@@ -116,3 +121,53 @@ class Model(Transformer):
"""
__metaclass__ = ABCMeta
+
+
+@inherit_doc
+class UnaryTransformer(HasInputCol, HasOutputCol, Transformer):
+ """
+ Abstract class for transformers that tae one input column, apply a
transoformation to it,
+ and output the result as a new column.
+
+ .. versionadded:: 2.3.0
+ """
+
+ @abstractmethod
+ def createTransformFunc(self):
+ """
+ Creates the transoform function using the given param map.
+ """
+ raise NotImplementedError()
+
+ @abstractmethod
+ def outputDataType(self):
+ """
+ Returns the data type of the output column as a sql type
+ """
+ raise NotImplementedError()
+
+ @abstractmethod
+ def validateInputType(self, inputType):
+ """
+ Validates the input type. Throws an exception if it is invalid.
+ """
+ raise NotImplementedError()
+
+ def transformSchema(self, schema):
+ inputType = schema[self.getInputCol()].dataType
+ self.validateInputType(inputType)
+ if self.getOutputCol() in schema.names:
+ raise ValueError("Output column %s already exists." %
self.getOutputCol())
+ outputFields = copy.copy(schema.fields)
+ outputFields.append(StructField(self.getOutputCol(),
+ self.outputDataType(),
+ nullable=False))
+ return StructType(outputFields)
+
+ def _transform(self, dataset):
+ self.transformSchema(dataset.schema)
+ transformFunc = self.createTransformFunc()
--- End diff --
remove
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