mik-laj commented on a change in pull request #7718: [AIRFLOW-5421] Add Presto to GCS transfer operator URL: https://github.com/apache/airflow/pull/7718#discussion_r394272846
########## File path: airflow/providers/google/cloud/operators/presto_to_gcs.py ########## @@ -0,0 +1,212 @@ +# +# 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 airflow.providers.google.cloud.operators.sql_to_gcs import BaseSQLToGCSOperator +from airflow.providers.presto.hooks.presto import PrestoHook +from airflow.utils.decorators import apply_defaults + + +class _AirflowPrestoCursorAdapter: + """ + An adapter that adds additional feature to the Presto cursor. + + The implementation of cursor in the prestodb library is not sufficient. + The following changes have been made: + + * The poke mechanism for row. You can look at the next row without consuming it. + * The description attribute is available before reading the first row. Thanks to the poke mechanism. + * the iterator interface has been implemented. + + A detailed description of the class methods is available in + `PEP-249 <https://www.python.org/dev/peps/pep-0249/>`__. + """ + + def __init__(self, cursor): + self.cursor = cursor + self.rows = [] + self.initialized = False + + @property + def description(self): + """ + This read-only attribute is a sequence of 7-item sequences. + + Each of these sequences contains information describing one result column: + + * ``name`` + * ``type_code`` + * ``display_size`` + * ``internal_size`` + * ``precision`` + * ``scale`` + * ``null_ok`` + + The first two items (``name`` and ``type_code``) are mandatory, the other + five are optional and are set to None if no meaningful values can be provided. + """ + if not self.initialized: + # Peek for first row to load description. + self.peekone() + return self.cursor.description + + @property + def rowcount(self): + """The read-only attribute specifies the number of rows""" + return self.cursor.rowcount + + def close(self): + """Close the cursor now""" + return self.cursor.close() + + def execute(self, *args, **kwwargs): + """Prepare and execute a database operation (query or command).""" + self.initialized = False + self.rows = [] + return self.cursor.execute(*args, **kwwargs) + + def executemany(self, *args, **kwargs): + """ + Prepare a database operation (query or command) and then execute it against all parameter + sequences or mappings found in the sequence seq_of_parameters. + """ + self.initialized = False + self.rows = [] + return self.cursor.executemany(*args, **kwargs) + + def peekone(self): + """ + Return the next row without consuming it. + """ + self.initialized = True + element = self.cursor.fetchone() + self.rows.insert(0, element) + return element + + def fetchone(self): + """ + Fetch the next row of a query result set, returning a single sequence, or + ``None`` when no more data is available. + """ + if self.rows: + return self.rows.pop(0) + return self.cursor.fetchone() + + def fetchmany(self, size=None): + """ + Fetch the next set of rows of a query result, returning a sequence of sequences + (e.g. a list of tuples). An empty sequence is returned when no more rows are available. + """ + if size is None: + size = self.cursor.arraysize + + result = [] + for _ in range(size): + row = self.fetchone() + if row is None: + break + result.append(row) + + return result + + def __next__(self): + """ + Return the next row from the currently executing SQL statement using the same semantics as + ``.fetchone()``. A ``StopIteration`` exception is raised when the result set is exhausted. + :return: + """ + result = self.fetchone() + if result is None: + raise StopIteration() + return result + + def __iter__(self): + """ + Return self to make cursors compatible to the iteration protocol + """ + return self + + +class PrestoToGCSOperator(BaseSQLToGCSOperator): + """Copy data from PrestoDB to Google Cloud Storage in JSON or CSV format. + + :param presto_conn_id: Reference to a specific Presto hook. + :type presto_conn_id: str + """ + + ui_color = "#a0e08c" + + type_map = { + "BOOLEAN": "BOOL", + "TINYINT": "INT64", + "SMALLINT": "INT64", + "INTEGER": "INT64", + "BIGINT": "INT64", + "REAL": "FLOAT64", + "DOUBLE": "FLOAT64", + "DECIMAL": "NUMERIC", + "VARCHAR": "STRING", + "CHAR": "STRING", + "VARBINARY": "BYTES", + "JSON": "STRING", + "DATE": "DATE", + "TIME": "TIME", + # BigQuery don't time with timezone native. + "TIME WITH TIME ZONE": "STRING", + "TIMESTAMP": "TIMESTAMP", + # BigQuery supports a narrow range of time zones during import. + # You should use TIMESTAMP function, if you want have TIMESTAMP type + "TIMESTAMP WITH TIME ZONE": "STRING", + "IPADDRESS": "STRING", + "UUID": "STRING", + } + + @apply_defaults + def __init__(self, presto_conn_id="presto_default", *args, **kwargs): + super().__init__(*args, **kwargs) + self.presto_conn_id = presto_conn_id + + def query(self): + """ + Queries presto and returns a cursor to the results. + """ + presto = PrestoHook(presto_conn_id=self.presto_conn_id) + conn = presto.get_conn() + cursor = conn.cursor() + self.log.info("Executing: %s", self.sql) + cursor.execute(self.sql) + return _AirflowPrestoCursorAdapter(cursor) + + def field_to_bigquery(self, field): Review comment: Types are available in the base class. the mypy and other tools can identify types because they are abstract methods. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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