refactor: use unique constraints instead of composite keys on link tables

backend/src/chitai/database/models/author.py

@@ -1,7 +1,7 @@
 from typing import TYPE_CHECKING, Optional
 from collections.abc import Hashable
 
-from sqlalchemy import ColumnElement, ForeignKey
+from sqlalchemy import ColumnElement, ForeignKey, UniqueConstraint
 from sqlalchemy.orm import Mapped
 from sqlalchemy.orm import mapped_column
 from sqlalchemy.orm import relationship
@@ -35,11 +35,10 @@ class Author(BigIntAuditBase, UniqueMixin):
 
 class BookAuthorLink(BigIntBase):
     __tablename__ = "book_author_links"
+    __table_args__ = (UniqueConstraint("book_id", "author_id"),)
 
-    book_id: Mapped[int] = mapped_column(
-        ForeignKey("books.id", ondelete="cascade"), primary_key=True
-    )
-    author_id: Mapped[int] = mapped_column(ForeignKey("authors.id"), primary_key=True)
+    book_id: Mapped[int] = mapped_column(ForeignKey("books.id", ondelete="cascade"))
+    author_id: Mapped[int] = mapped_column(ForeignKey("authors.id"))
 
     position: Mapped[int]
 

backend/src/chitai/database/models/book.py

@@ -1,8 +1,7 @@
 from datetime import date
 from typing import TYPE_CHECKING, Any, Optional
 
-from sqlalchemy import Index
-from sqlalchemy import ForeignKey
+from sqlalchemy import Index, ForeignKey, UniqueConstraint
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 from sqlalchemy.orm import mapped_column
 from sqlalchemy.orm import relationship
@@ -127,11 +126,10 @@ class Book(BigIntAuditBase):
 
 class Identifier(BigIntBase):
     __tablename__ = "identifiers"
+    __table_args__ = (UniqueConstraint("name", "book_id"),)
 
-    name: Mapped[str] = mapped_column(primary_key=True)
-    book_id: Mapped[int] = mapped_column(
-        ForeignKey("books.id", ondelete="cascade"), primary_key=True
-    )
+    name: Mapped[str]
+    book_id: Mapped[int] = mapped_column(ForeignKey("books.id", ondelete="cascade"))
     value: Mapped[str]
 
     def __repr__(self):

backend/src/chitai/database/models/book_list.py

@@ -1,5 +1,5 @@
 from typing import Optional
-from sqlalchemy import ForeignKey
+from sqlalchemy import ForeignKey, UniqueConstraint
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 from sqlalchemy.ext.associationproxy import association_proxy, AssociationProxy
 from sqlalchemy.ext.orderinglist import ordering_list
@@ -38,10 +38,10 @@ class BookList(BigIntAuditBase):
 
 class BookListLink(BigIntBase):
     __tablename__ = "book_list_links"
-    book_id: Mapped[int] = mapped_column(
-        ForeignKey("books.id", ondelete="cascade"), primary_key=True
-    )
-    list_id: Mapped[int] = mapped_column(ForeignKey("book_lists.id"), primary_key=True)
+    __table_args__ = (UniqueConstraint("book_id", "list_id"),)
+
+    book_id: Mapped[int] = mapped_column(ForeignKey("books.id", ondelete="cascade"))
+    list_id: Mapped[int] = mapped_column(ForeignKey("book_lists.id"))
     position: Mapped[int]
 
     book: Mapped[Book] = relationship(back_populates="list_links")

backend/src/chitai/database/models/tag.py

@@ -1,7 +1,7 @@
 from collections.abc import Hashable
 from typing import TYPE_CHECKING
 
-from sqlalchemy import ColumnElement, ForeignKey
+from sqlalchemy import ColumnElement, ForeignKey, UniqueConstraint
 from sqlalchemy.orm import Mapped
 from sqlalchemy.orm import mapped_column
 from sqlalchemy.orm import relationship
@@ -35,15 +35,12 @@ class Tag(BigIntBase, UniqueMixin):
 
 class BookTagLink(BigIntBase):
     __tablename__ = "book_tag_link"
+    __table_args__ = (UniqueConstraint("book_id", "tag_id"),)
 
-    book_id: Mapped[int] = mapped_column(
-        ForeignKey("books.id", ondelete="cascade"), primary_key=True
-    )
-
-    tag_id: Mapped[int] = mapped_column(ForeignKey("tags.id"), primary_key=True)
+    book_id: Mapped[int] = mapped_column(ForeignKey("books.id", ondelete="cascade"))
+    tag_id: Mapped[int] = mapped_column(ForeignKey("tags.id"))
 
     position: Mapped[int]
 
     book: Mapped["Book"] = relationship(back_populates="tag_links")
-
     tag: Mapped[Tag] = relationship()