HyukjinKwon commented on a change in pull request #33484: URL: https://github.com/apache/spark/pull/33484#discussion_r676069606
########## File path: python/pyspark/sql/observation.py ########## @@ -0,0 +1,147 @@ +# +# Licensed to the Apache Software Foundation (ASF) under one or more +# contributor license agreements. See the NOTICE file distributed with +# this work for additional information regarding copyright ownership. +# The ASF licenses this file to You under the Apache License, Version 2.0 +# (the "License"); you may not use this file except in compliance with +# the License. You may obtain a copy of the License at +# +# http://www.apache.org/licenses/LICENSE-2.0 +# +# Unless required by applicable law or agreed to in writing, software +# distributed under the License is distributed on an "AS IS" BASIS, +# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +# See the License for the specific language governing permissions and +# limitations under the License. +# +from uuid import uuid4 + +from pyspark.sql import column, Column, DataFrame, Row + +basestring = unicode = str + +__all__ = ["Observation"] + + +class Observation: + """Class to observe (named) metrics on a :class:`DataFrame`. + + Metrics are aggregation expressions, which are applied to the DataFrame while is is being + processed by an action. + + .. versionadded:: 3.3.0 + + The metrics have the following guarantees: + + - It will compute the defined aggregates (metrics) on all the data that is flowing through + the Dataset during the action. + - It will report the value of the defined aggregate columns as soon as we reach the end of + the action. + + The metrics columns must either contain a literal (e.g. lit(42)), or should contain one or + more aggregate functions (e.g. sum(a) or sum(a + b) + avg(c) - lit(1)). Expressions that + contain references to the input Dataset's columns must always be wrapped in an aggregate + function. + + An Observation instance collects the metrics while the first action is executed. Subsequent + actions do not modify the metrics returned by `Observation.get`. Retrieval of the metric via + `Observation.get` blocks until the first action has finished and metrics become available. + + This class does not support streaming datasets. + + Examples + -------- + >>> from pyspark.sql.functions import col, count, lit, max + >>> from pyspark.sql.observation import Observation + >>> observation = Observation("my_metrics") + >>> observed_df = df.observe(observation, count(lit(1)).alias("count"), max(col("age"))) + >>> observed_df.count() + 2 + >>> observation.get + Row(count=2, max(age)=5) + """ + def __init__(self, name=None): + """Constructs a named or unnamed Observation instance. + + Parameters + ---------- + name : str, optional + default is a random UUID string. This is the name of the Observation and the metric. + """ + assert isinstance(name, basestring), "name should be a string" + self._name = name or str(uuid4()) + self._jvm = None + self._jo = None + + def _on(self, df, *exprs): + """Attaches this observation to the given :class:`DataFrame` to observe aggregations. + + Parameters + ---------- + df : :class:`DataFrame` + the :class:`DataFrame` to be observed + exprs : list of :class:`Column` + column expressions (:class:`Column`). + + Returns + ------- + :class:`DataFrame` + the observed :class:`DataFrame`. + """ + assert exprs, "exprs should not be empty" + assert all(isinstance(c, Column) for c in exprs), "all exprs should be Column" + assert self._jo is None, "an Observation can be used with a DataFrame only once" + + self._jvm = df._sc._jvm + self._jo = self._jvm.org.apache.spark.sql.Observation(self._name) Review comment: I think we don't need to create uuid in Python side. Just call `self._jvm.org.apache.spark.sql.Observation()` if name is not given. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
