chore: use Singer in sample

Author: olavloite

samples/model.py

@@ -77,21 +77,6 @@ class Singer(Base):
     concerts: Mapped[List["Concert"]] = relationship(
         back_populates="singer", cascade="all, delete-orphan"
     )
-    # Create a commit timestamp column and set a client-side default of
-    # PENDING_COMMIT_TIMESTAMP() An event handler below is responsible for
-    # setting PENDING_COMMIT_TIMESTAMP() on updates. If using SQLAlchemy
-    # core rather than the ORM, callers will need to supply their own
-    # PENDING_COMMIT_TIMESTAMP() values in their inserts & updates.
-    last_update_time: Mapped[datetime.datetime] = mapped_column(
-        spanner_allow_commit_timestamp=True,
-        default=text("PENDING_COMMIT_TIMESTAMP()"),
-    )
-
-
-@event.listens_for(TimestampUser, "before_update")
-def singer_before_update(mapper, connection, target):
-    """Updates the commit timestamp when the row is updated."""
-    target.updated_at = text("PENDING_COMMIT_TIMESTAMP()")
 
 
 class Album(Base):
@@ -194,3 +179,18 @@ class TicketSale(Base):
         DateTime, nullable=False
     )
     singer_id: Mapped[str] = mapped_column(String(36), ForeignKey("singers.id"))
+    # Create a commit timestamp column and set a client-side default of
+    # PENDING_COMMIT_TIMESTAMP() An event handler below is responsible for
+    # setting PENDING_COMMIT_TIMESTAMP() on updates. If using SQLAlchemy
+    # core rather than the ORM, callers will need to supply their own
+    # PENDING_COMMIT_TIMESTAMP() values in their inserts & updates.
+    last_update_time: Mapped[datetime.datetime] = mapped_column(
+        spanner_allow_commit_timestamp=True,
+        default=text("PENDING_COMMIT_TIMESTAMP()"),
+    )
+
+
+@event.listens_for(TicketSale, "before_update")
+def ticket_sale_before_update(mapper, connection, target):
+    """Updates the commit timestamp when the row is updated."""
+    target.last_update_time = text("PENDING_COMMIT_TIMESTAMP()")