挂起可能涉及MySQL表本身，而不涉及Python代码.它们包含很多记录吗?他们的桌子很宽吗?它们是否在datetime_field上建立索引?

Hanging could involve the MySQL tables themselves and not specifically the Python code. Do they contain many records? Are they very wide tables? Are they indexed on the datetime_field?

考虑各种策略:

1. 具体选择所需的列而不是星号，从而调用所有列.

1. Specifically select the needed columns instead of the asterisk, calling all columns.

DBR_DATETIME_FIELD上的索引，用于where子句(即隐式连接).

Index on the DBR_DATETIME_FIELD being used in the where clause (i.e., implicit join).

使用打印的计时器print(datetime.datetime.now())进一步诊断，以查看哪些是瓶颈表.为此，请确保导入datetime模块.

Diagnose further with printed timers print(datetime.datetime.now()) to see which are the bottleneck tables. In doing so, be sure to import the datetime module.