OmerJog commented on a change in pull request #6604: [AIRFLOW-5920] Neo4j operator and hook URL: https://github.com/apache/airflow/pull/6604#discussion_r354323867
########## File path: airflow/contrib/operators/neo4j_operator.py ########## @@ -0,0 +1,107 @@ +# -*- coding: utf-8 -*- +# +# 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. +""" +Neo4JOperator to interact and perform action on Neo4J graph database. +This operator is designed to use Neo4J Hook and the +Python driver: https://neo4j.com/docs/api/python-driver/current/ +""" + +import csv + +from neo4j import BoltStatementResult + +from airflow.contrib.hooks.neo4j_hook import Neo4JHook +from airflow.exceptions import AirflowException +from airflow.models import BaseOperator +from airflow.utils.decorators import apply_defaults + + +class Neo4JOperator(BaseOperator): + """ + This operator takes a number of configuration parameters + :param cypher_query: required cypher query to be executed on the Neo4J database + :type cypher_query: str + :param output_filename: required filename to produce with output from the query + :type output_filename: str + :param n4j_conn_id: reference to a pre-defined Neo4J Connection + :type n4j_conn_id: str + :param fail_on_no_results: True/False flag to indicate if it should fail the task if no results + :type fail_on_no_results: bool + """ + _cypher_query = None + _output_filename = None + _n4j_conn_id = None + _fail_on_no_results = None + + template_fields = ['cypher_query', 'output_filename', 'n4j_conn_id'] + + @apply_defaults + def __init__(self, + cypher_query, + output_filename, + n4j_conn_id, + fail_on_no_results=False, + *args, + **kwargs): + super().__init__(*args, **kwargs) + + self._output_filename = output_filename + self._cypher_query = cypher_query + self._n4j_conn_id = n4j_conn_id + self._fail_on_no_results = fail_on_no_results + + def execute(self, context): + """ + Executes the supplied query and saves the results as a CSV file on disk + :param context: + :return: + """ + hook = Neo4JHook(n4j_conn_id=self._n4j_conn_id) + result: BoltStatementResult = hook.run_query(cypher_query=self._cypher_query) + + # In some cases, an empty result should fail (where results are expected) + if result.peek() is None and self._fail_on_no_results: + raise AirflowException("Query returned no rows") + + row_count = self._make_csv(result) + + # Provide some feedback to what was done... + self.log.info("Saved %s with %s rows", self._output_filename, row_count) + + def _make_csv(self, result: BoltStatementResult): Review comment: Think of case where you would want to export neo4j data (for backup or other) now you can export it to local file, GCS, S3, FTP and the list is long. If this function remains on the Operator each one will need to duplicate the logic. On the other hand if the function is on the hook all operators that use the hook will be able to use it. This is why most of the db hook has this method in them (and other like get_pandas_df ) By the way most hooks call this method `to_csv` better to stay consistent. ---------------------------------------------------------------- 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. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services
