将 BigQuery 表导出到 Google Storage 时如何避免标头

Posted 2023-03-24

【中文标题】将 BigQuery 表导出到 Google Storage 时如何避免标头

【英文标题】：How to avoid header while exporting BigQuery table in to Google Storage

【发布时间】：2019-05-16 05:06:48

【问题描述】：

我开发了以下代码，有助于将 BigQuery 表导出到 Google 存储桶。我想将文件合并到没有标题的单个文件中，以便下一个进程将使用文件而没有任何问题。

    def export_bq_table_to_gcs(self, table_name):
        client = bigquery.Client(project=project_name)

        print("Exporting table ".format(table_name))
        dataset_ref = client.dataset(dataset_name,
                                     project=project_name)
        dataset = bigquery.Dataset(dataset_ref)
        table_ref = dataset.table(table_name)
        size_bytes = client.get_table(table_ref).num_bytes

        # For tables bigger than 1GB uses Google auto split, otherwise export is forced in a single file.
        if size_bytes > 10 ** 9:
            destination_uris = [
                      'gs:///*.csv'.format(bucket_name,
                                       f'table_name_temp', uid)]
        else:
            destination_uris = [
                      'gs:///.csv'.format(bucket_name,
                                      f'table_name_temp', uid)]

        extract_job = client.extract_table(table_ref, destination_uris)  # API request
        result = extract_job.result()  # Waits for job to complete.

        if result.state != 'DONE' or result.errors:
            raise Exception('Failed extract job  for table '.format(result.job_id, table_name))
        else:
            print('BQ table(s) export completed successfully')
        storage_client = storage.Client(project=gs_project_name)
        bucket = storage_client.get_bucket(gs_bucket_name)
        blob_list = bucket.list_blobs(prefix=f'table_name_temp')
        print('Merging shard files into single file')
        bucket.blob(f'table_name.csv').compose(blob_list)

你能帮我找到跳过标题的方法吗？

谢谢，

拉古纳特。

【参考方案1】：

我们可以通过使用 jobConfig 将 print_header 参数设置为 False 来避免 header。示例代码

job_config = bigquery.job.ExtractJobConfig(print_header=False)
extract_job = client.extract_table(table_ref, destination_uris,
                                   job_config=job_config)

谢谢

【参考方案2】：

您可以使用skipLeadingRows (https://cloud.google.com/bigquery/docs/reference/rest/v2/tables#externalDataConfiguration.googleSheetsOptions.skipLeadingRows)

【讨论】：

我正在导出 BQ 表，我猜你共享选项可在将 CSV 导入 BQ 表时使用。如果我误解了，请告诉我