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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Support arrays of record/structs as query parameters","articleBody":"Thanks for stopping by to let us know something could be better!\r\n\r\n**PLEASE READ**: If you have a support contract with Google, please create an issue in the [support console](https://cloud.google.com/support/) instead of filing on GitHub. This will ensure a timely response.\r\n\r\n **Is your feature request related to a problem? Please describe.**\r\n Setting nested repeated fields via the python-bigquery API works (despite not being documented by [ArrayQueryParameter](https://googleapis.dev/python/bigquery/latest/generated/google.cloud.bigquery.query.ArrayQueryParameter.html#google.cloud.bigquery.query.ArrayQueryParameter)).\r\n[ArrayQueryParamter.to_api_repr](https://googleapis.dev/python/bigquery/latest/_modules/google/cloud/bigquery/query.html#ArrayQueryParameter.to_api_repr) has code to handle \"RECORD\" or \"STRUCT\" but doesn't check if the array is empty and so throw exceptions.\r\n  \r\n **Describe the solution you'd like**\r\nI'd a way to define the schema for the array of records so that it doesn't matter that it's empty - I can still use the BQ python client. There appears to be solutions  for typed languages https://github.com/googleapis/google-cloud-java/issues/2678 as well as dynamic languages https://github.com/googleapis/google-cloud-ruby/pull/4269 and losely typed languages https://github.com/googleapis/nodejs-bigquery/issues/400.\r\n\r\n **Describe alternatives you've considered**\r\nOur current solution involves naming each individual field in the repeated struct  (eg fieldA_0, fieldB_0, fieldA_1,...)\r\nand sending over MANY query parameters. As there's a limit to the number of named parameters the API allows, this is far from perfect and makes our code significantly harder to read and understand.\r\n\r\n **Additional context**\r\n```python\r\nfrom google.cloud import bigquery\r\nclient = bigquery.Client()\r\n\r\ndef query(params):\r\n    sql = \"SELECT * FROM UNNEST(@params) as param\"\r\n    query_parameter = bigquery.ArrayQueryParameter(\r\n                \"params\",\r\n                \"RECORD\",\r\n                [\r\n                    bigquery.StructQueryParameter.positional(\r\n                        bigquery.ScalarQueryParameter(\"key\", \"STRING\", key),\r\n                        bigquery.ScalarQueryParameter(\"value\", \"STRING\", value),\r\n                    )\r\n                    for key, value in (params.items())\r\n                ],\r\n    )\r\n    for row in client.query(sql, job_config=bigquery.QueryJobConfig(query_parameters=[query_parameter])):\r\n        print(dict(row))\r\n\r\nquery({\"one\": \"a\", \"two\": \"b\"}) # works\r\nquery({}) # IndexError: list index out of range\r\n``` ","author":{"url":"https://github.com/michellen-hf","@type":"Person","name":"michellen-hf"},"datePublished":"2021-01-08T05:41:51.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/463/python-bigquery/issues/463"}