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Posted to commits@airflow.apache.org by GitBox <gi...@apache.org> on 2020/03/11 21:07:22 UTC
[GitHub] [airflow] mik-laj commented on a change in pull request #6788:
[AIRFLOW-5944] Display rendered template_fields without accessing DAG files
mik-laj commented on a change in pull request #6788: [AIRFLOW-5944] Display rendered template_fields without accessing DAG files
URL: https://github.com/apache/airflow/pull/6788#discussion_r391268396
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File path: airflow/models/renderedtifields.py
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@@ -0,0 +1,135 @@
+#
+# 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.
+"""Save Rendered Template Fields """
+from typing import Optional
+
+import sqlalchemy_jsonfield
+from sqlalchemy import Column, String, and_, tuple_
+from sqlalchemy.orm import Session
+
+from airflow.configuration import conf
+from airflow.models.base import ID_LEN, Base
+from airflow.models.taskinstance import TaskInstance
+from airflow.serialization.helpers import serialize_template_field
+from airflow.settings import json
+from airflow.utils.session import provide_session
+from airflow.utils.sqlalchemy import UtcDateTime
+
+
+class RenderedTaskInstanceFields(Base):
+ """
+ Save Rendered Template Fields
+ """
+
+ __tablename__ = "rendered_task_instance_fields"
+
+ dag_id = Column(String(ID_LEN), primary_key=True)
+ task_id = Column(String(ID_LEN), primary_key=True)
+ execution_date = Column(UtcDateTime, primary_key=True)
+ rendered_fields = Column(sqlalchemy_jsonfield.JSONField(json=json), nullable=False)
+
+ def __init__(self, ti: TaskInstance, render_templates=True):
+ self.dag_id = ti.dag_id
+ self.task_id = ti.task_id
+ self.task = ti.task
+ self.execution_date = ti.execution_date
+ self.ti = ti
+ if render_templates:
+ ti.render_templates()
+ self.rendered_fields = {
+ field: serialize_template_field(
+ getattr(self.task, field)
+ ) for field in self.task.template_fields
+ }
+
+ def __repr__(self):
+ return f"<{self.__class__.__name__}: {self.dag_id}.{self.task_id} {self.execution_date}"
+
+ @classmethod
+ @provide_session
+ def get_templated_fields(cls, ti: TaskInstance, session: Session = None) -> Optional[dict]:
+ """
+ Get templated field for a TaskInstance from the RenderedTaskInstanceFields
+ table.
+
+ :param ti: Task Instance
+ :param session: SqlAlchemy Session
+ :return: Rendered Templated TI field
+ """
+ result = session.query(cls.rendered_fields).filter(
+ cls.dag_id == ti.dag_id,
+ cls.task_id == ti.task_id,
+ cls.execution_date == ti.execution_date
+ ).one_or_none()
+
+ if result:
+ rendered_fields = result.rendered_fields
+ return rendered_fields
+ else:
+ return None
+
+ @provide_session
+ def write(self, session: Session = None):
+ """Write instance to database
+
+ :param session: SqlAlchemy Session
+ """
+ session.merge(self)
+
+ @classmethod
+ @provide_session
+ def delete_old_records(
+ cls, task_id: str, dag_id: str,
+ num_to_keep=conf.getint("core", "max_num_rendered_ti_fields_per_task", fallback=0),
+ session: Session = None
+ ):
+ """
+ Keep only Last X (num_to_keep) number of records for a task by deleting others
+
+ :param task_id: Task ID
+ :param dag_id: Dag ID
+ :param num_to_keep: Number of Records to keep
+ :param session: SqlAlchemy Session
+ """
+ if num_to_keep > 0:
+ # Fetch Top X records given dag_id & task_id ordered by Execution Date
+ subq1 = (
+ session
+ .query(cls.dag_id, cls.task_id, cls.execution_date)
+ .filter(cls.dag_id == dag_id, cls.task_id == task_id)
+ .order_by(cls.execution_date.desc())
+ .limit(num_to_keep)
+ .subquery('subq1')
+ )
+
+ # Second Subquery
+ # Workaround for MySQL Limitation (https://stackoverflow.com/a/19344141/5691525)
+ # Limitation: This version of MySQL does not yet support
+ # LIMIT & IN/ALL/ANY/SOME subquery
+ subq2 = (
+ session
+ .query(subq1.c.dag_id, subq1.c.task_id, subq1.c.execution_date)
+ .subquery('subq2')
+ )
+
+ session.query(cls) \
+ .filter(and_(
+ cls.dag_id == dag_id,
+ cls.task_id == task_id,
+ tuple_(cls.dag_id, cls.task_id, cls.execution_date).notin_(subq2))) \
Review comment:
Tuple is problematic. It is not supported by all RDMS.
```
The composite IN construct is not supported by all backends, and is
currently known to work on PostgreSQL, MySQL, and SQLite.
Unsupported backends will raise a subclass of
:class:`~sqlalchemy.exc.DBAPIError` when such an expression is
invoked.
``` We don't use this syntax elsewhere. Do you really need to use it here?
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