René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"BigQuery: Client.query modifies job_config object","articleBody":"#### Steps to reproduce\r\n\r\n  1. Create a `QueryJobConfig` object.\r\n  2. Pass the object to the `Client.query` method.\r\n  3. Observe that the configuration object has changed.\r\n\r\n#### Code example\r\n\r\n```python\r\nfrom google.cloud import bigquery\r\n\r\nclient = bigquery.Client()\r\nconfig = bigquery.QueryJobConfig(dry_run=True)\r\njob = client.query(\r\n    \"\"\"\r\n    SELECT name, SUM(number) AS total_people\r\n    FROM `bigquery-public-data.usa_names.usa_1910_current`\r\n    GROUP BY name\r\n    \"\"\",\r\n    job_config=config\r\n)\r\nprint(job.total_bytes_processed)\r\n\r\nconfig.dry_run = False\r\njob = client.query(\r\n    \"\"\"\r\n    SELECT name, SUM(number) AS total_people\r\n    FROM `bigquery-public-data.usa_names.usa_1910_current`\r\n    GROUP BY name\r\n    \"\"\",\r\n    job_config=config\r\n)\r\njob.result()\r\n```\r\n\r\n#### Stack trace\r\n```\r\n---------------------------------------------------------------------------\r\nBadRequest                                Traceback (most recent call last)\r\n\u003cipython-input-17-97f4f20faa6a\u003e in \u003cmodule\u003e\r\n----\u003e 1 job.result()\r\n\r\n~/miniconda3/envs/scratch/lib/python3.7/site-packages/google/cloud/bigquery/job.py in result(self, timeout, page_size, retry, max_results)\r\n   2937         \"\"\"\r\n   2938         try:\r\n-\u003e 2939             super(QueryJob, self).result(timeout=timeout)\r\n   2940 \r\n   2941             # Return an iterator instead of returning the job.\r\n\r\n~/miniconda3/envs/scratch/lib/python3.7/site-packages/google/cloud/bigquery/job.py in result(self, timeout, retry)\r\n    732             self._begin(retry=retry)\r\n    733         # TODO: modify PollingFuture so it can pass a retry argument to done().\r\n--\u003e 734         return super(_AsyncJob, self).result(timeout=timeout)\r\n    735 \r\n    736     def cancelled(self):\r\n\r\n~/miniconda3/envs/scratch/lib/python3.7/site-packages/google/api_core/future/polling.py in result(self, timeout)\r\n    125             # pylint: disable=raising-bad-type\r\n    126             # Pylint doesn't recognize that this is valid in this case.\r\n--\u003e 127             raise self._exception\r\n    128 \r\n    129         return self._result\r\n\r\nBadRequest: 400 Cannot explicitly modify anonymous table swast-scratch:_def2aa82a75fc33513bfb65968607e1f49148f83.anon561d4b35377f56c5960a4a49be253d3c90c120db\r\n\r\n(job ID: 2692472c-1213-4716-8393-d9c49fd7b678)\r\n\r\n                -----Query Job SQL Follows-----                \r\n\r\n    |    .    |    .    |    .    |    .    |    .    |\r\n   1:\r\n   2:    SELECT name, SUM(number) AS total_people\r\n   3:    FROM `bigquery-public-data.usa_names.usa_1910_current`\r\n   4:    GROUP BY name\r\n   5:    \r\n    |    .    |    .    |    .    |    .    |    .    |\r\n```\r\n\r\nWhen you run a job, the configuration object may be modified. In this example, it sets the destination table. It is unexpected that the original Python object would be modified.\r\n\r\nI propose that the `query` (and other \"job\" methods on client) be updated to make a deep copy of the the `job_config` argument before passing it on to the job constructor.","author":{"url":"https://github.com/tswast","@type":"Person","name":"tswast"},"datePublished":"2019-11-11T19:25:20.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/9727/google-cloud-python/issues/9727"}