优化数据库模型与关系

models/share.py

@@ -2,7 +2,7 @@
 
 from typing import Optional, TYPE_CHECKING
 from datetime import datetime
-from sqlmodel import Field, Relationship, text, Column, func, DateTime
+from sqlmodel import Field, Relationship, text, CheckConstraint, UniqueConstraint, Index
 from .base import TableBase
 from datetime import datetime
 
@@ -12,10 +12,20 @@ if TYPE_CHECKING:
 
 class Share(TableBase, table=True):
     __tablename__ = 'shares'
+    __table_args__ = (
+        UniqueConstraint("code", name="uq_share_code"),
+        CheckConstraint("(file_id IS NOT NULL) <> (folder_id IS NOT NULL)", name="ck_share_xor"),
+        Index("ix_share_source_name", "source_name"),
+        Index("ix_share_user_created", "user_id", "created_at"),
+    )
 
+    code: str = Field(max_length=64, nullable=False, index=True, description="分享码")
     password: Optional[str] = Field(default=None, max_length=255, description="分享密码（加密后）")
+    
     is_dir: bool = Field(default=False, sa_column_kwargs={"server_default": text("false")}, description="是否为目录分享")
-    source_id: int = Field(description="源文件或目录的ID")
+    file_id: Optional[int] = Field(default=None, foreign_key="files.id", index=True, description="文件ID（二选一）")
+    folder_id: Optional[int] = Field(default=None, foreign_key="folders.id", index=True, description="目录ID（二选一）")
+    
     views: int = Field(default=0, sa_column_kwargs={"server_default": "0"}, description="浏览次数")
     downloads: int = Field(default=0, sa_column_kwargs={"server_default": "0"}, description="下载次数")
     remain_downloads: Optional[int] = Field(default=None, description="剩余下载次数 (NULL为不限制)")