Fix table updates

src/audio_feeder/sql_database_handler.py

@@ -300,21 +300,45 @@ def _save_table(
     ) -> None:
         table_type = oh.TYPE_MAPPING[oh.TABLE_MAPPING[table_name]]
 
+        # Delete anything not in `table_contents`
         stmt = sa.delete(table_type).where(
             sa.column("id").not_in(table_contents.keys())
         )
         session.execute(stmt)
 
-        try:
-            session.add_all(list(table_contents.values()))
-        except orm.exc.UnmappedInstanceError:
-            # If the instances were created before the ORM mapping was set up,
-            # instrumentation won't be set up on the instances, so we need to
-            # create new copies of the instances (at least until we find a
-            # better way to do this.
-            session.add_all(
-                [table_entry.copy() for table_entry in table_contents.values()]
+        # Find all the objects that have been modified, either by mutating them
+        # in-place, replacing them with a new schema object or because they
+        # are new to the table.
+        to_update: typing.MutableMapping[ID, ot.SchemaObject] = {}
+        to_replace: typing.MutableMapping[ID, ot.SchemaObject] = {}
+
+        for key, obj in table_contents.items():
+            insp = sa.inspect(obj)
+            if insp.modified:
+                if insp.has_identity:
+                    # These objects already exist in the table
+                    to_update[key] = obj
+                else:
+                    # These are either new or are using a new instance
+                    to_replace[key] = obj
+
+        if to_replace:
+            # Delete all rows where the object in the table dictionary is using
+            # a new instance.
+            replace_stmt = sa.delete(table_type).where(
+                sa.column("id").in_(to_replace.keys())
             )
+            session.execute(replace_stmt)
+
+        for to_add in (to_replace, to_update):
+            try:
+                session.add_all(to_add.values())
+            except orm.exc.UnmappedInstanceError:
+                # If the instances were created before the ORM mapping was set
+                # up, instrumentation won't be set up on the instances, so we
+                # need to create new copies of the instances (at least until we
+                # find a better way to do this.
+                session.add_all([table_entry.copy() for table_entry in to_add.values()])
 
     def save_table(self, table_name: TableName, table_contents: Table) -> None:
         with self.session() as session:

tests/test_database_handlers.py

@@ -5,6 +5,7 @@
 import sqlite3
 import typing
 
+import attrs
 import pytest
 
 from audio_feeder import _db_types
@@ -148,6 +149,7 @@ def test_save_table(db_handler: _db_types.DatabaseHandler) -> None:
 
 
 def test_save_database_remove(db_handler: _db_types.DatabaseHandler) -> None:
+    """Test removing a key from the database."""
     db_tables = db_handler.load_database()
 
     book_ids = [book_id for book_id in db_tables["books"].keys()]
@@ -167,6 +169,39 @@ def test_save_database_remove(db_handler: _db_types.DatabaseHandler) -> None:
         assert book_id in books_table
 
 
+def test_update_database_mutate(db_handler: _db_types.DatabaseHandler) -> None:
+    db_tables = db_handler.load_database()
+
+    author_id, author = next(iter(db_tables["authors"].items()))
+    assert author.description is None
+    author.description = "The first author in the table"
+
+    db_handler.save_table("authors", db_tables["authors"])
+
+    author_table = db_handler.load_table("authors")
+    assert author_table[author_id].description == "The first author in the table"
+
+
+def test_update_database_replace(db_handler: _db_types.DatabaseHandler) -> None:
+    db_tables = db_handler.load_database()
+
+    ((book_id, book),) = filter(
+        lambda x: x[1].title == "Dracula", db_tables["books"].items()
+    )
+
+    book_kwargs = attrs.asdict(book)
+    book_kwargs["series_name"] = "Dracula"
+    book_kwargs["series_number"] = 1
+    replacement_book = oh.Book(**book_kwargs)
+    db_tables["books"][book_id] = replacement_book
+
+    db_handler.save_table("books", db_tables["books"])
+
+    books_table = db_handler.load_table("books")
+    assert books_table[book_id].series_name == "Dracula"
+    assert books_table[book_id].series_number == 1
+
+
 @pytest.mark.parametrize(
     "db_relpath, expected_version",
     (