table follow requires the id length of user

app/models/base.py

@@ -60,6 +60,11 @@ class AutoID:
     _id_prefix_len = 3   # 前缀长度
     _id_payload_len = 22 # 主体长度（ULID 转 Base62 最大约 22 位）
     
+    @classmethod
+    def id_length(cls) -> int:
+        """返回当前类 ID 的总长度"""
+        return cls._id_prefix_len + cls._id_payload_len
+    
     @declared_attr
     def id(cls):
         # 运行时动态获取子类的 __tablename__
@@ -74,4 +79,4 @@ class AutoID:
             payload = gen_convex_payload(length=s_len)
             return f"{prefix}{payload}"
 
-        return Column(String(p_len + s_len), primary_key=True, default=id_factory)
+        return Column(String(cls.id_length()), primary_key=True, default=id_factory)

app/models/follow.py

@@ -1,13 +1,28 @@
+from typing import TYPE_CHECKING
 from sqlalchemy import Column, DateTime, String, ForeignKey, UniqueConstraint
 from sqlalchemy.sql import func
 from .base import AutoID, Base
 
+# 只有在静态检查时才导入
+# 运行阶段这段代码会被跳过，彻底避免循环导入
+# 不确定是否用得上，但感觉这是个好习惯，尤其在模型之间有外键关系时
+if TYPE_CHECKING:
+    from .user import User
+
 class Follow(Base, AutoID):
     """用户关注关系表"""
     __tablename__ = "follows"
 
-    follower_id = Column(String(32), ForeignKey("users.id", ondelete="CASCADE"), index=True)
-    followee_id = Column(String(32), ForeignKey("users.id", ondelete="CASCADE"), index=True)
+    follower_id = Column(
+        String(User.id_length()), 
+        ForeignKey("users.id", ondelete="CASCADE"), 
+        index=True
+    )
+    followee_id = Column(
+        String(User.id_length()), 
+        ForeignKey("users.id", ondelete="CASCADE"), 
+        index=True
+    )
     
     created_at = Column(DateTime(timezone=True), server_default=func.now())