验证 BigQuery 表是否存在

Question

我有一个简单的函数来判断一个表是否存在：

def check_users_usersmetadata_existence():
    """
    Checks if the table Prod_UserUserMetadata exists
    """
    app_id = get_app_id()
    bigquery_client = bigquery.Client(project=app_id)
    dataset_ref = bigquery_client.dataset('Backup')
    table_ref = dataset_ref.table('Prod_UserUserMetadata')
    try:
        table = bigquery_client.get_table(table_ref)
        if table:
            print('Table {}\'s existence sucessfully proved!'.format(table_ref))
            return True
    except HttpError as error:
        raise
        print('Whoops! Table {} doesn\'t exist here! Ref: {}'.format(table_ref, error.resp.status))
        return False

问题是，它会在table = bigquery_client.get_table(table_ref) 这一行抛出 404，这没关系，因为该表不应该存在。但它不会继续处理脚本的其余部分。我试图在 try except 包装器中解析它，但它不起作用。我将如何解析这个？

Answer 1

您的脚本没有进入异常子句，因为它引发了 NotFound 错误而不是 HttpError。

这应该可行：

from google.cloud.exceptions import NotFound
def check_users_usersmetadata_existence():
    # (...)
    try:
        table = bigquery_client.get_table(table_ref)
        if table:
            print('Table {}\'s existence sucessfully proved!'.format(table_ref))
            return True
    except NotFound as error:
        # ...do some processing ...
        print('Whoops! Table {} doesn\'t exist here! Ref: {}'.format(table_ref, error.resp.status))
        return False

Answer 2

参见BigQuery Python客户端官方文档中的示例：https://googleapis.dev/python/bigquery/latest/usage/tables.html#getting-a-table

摘录：

from google.cloud import bigquery
from google.cloud.exceptions import NotFound

client = bigquery.Client()
# table_id = "your-project.your_dataset.your_table"

try:
    client.get_table(table_id)  # Make an API request.
    print("Table {} already exists.".format(table_id))
except NotFound:
    print("Table {} is not found.".format(table_id))

Answer 3

尝试使用 except NotFound NotFound 定义在https://github.com/googleapis/google-cloud-python/blob/release-core-1.3.0/api_core/google/api_core/exceptions.py#L219