lots of stuff

backend/models.py

@@ -1,3 +1,4 @@
+import uuid
 from datetime import UTC, date, datetime, time
 from enum import Enum as PyEnum
 from typing import TypedDict
@@ -16,6 +17,7 @@ from sqlalchemy import (
     UniqueConstraint,
     select,
 )
+from sqlalchemy.dialects.postgresql import UUID
 from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
@@ -328,9 +330,20 @@ class Exchange(Base):
     """Bitcoin exchange trades booked by users."""
 
     __tablename__ = "exchanges"
-    __table_args__ = (UniqueConstraint("slot_start", name="uq_exchange_slot_start"),)
+    # Note: No unique constraint on slot_start to allow cancelled bookings
+    # to be replaced. Application-level check in create_exchange ensures only
+    # one BOOKED trade per slot. For existing databases, manually drop the
+    # constraint: ALTER TABLE exchanges DROP CONSTRAINT IF EXISTS
+    # uq_exchange_slot_start;
 
     id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
+    public_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True),
+        nullable=False,
+        unique=True,
+        index=True,
+        default=uuid.uuid4,
+    )
     user_id: Mapped[int] = mapped_column(
         Integer, ForeignKey("users.id"), nullable=False, index=True
     )