Added db.index_foreign_keys() method plus test

sqlite_utils/cli.py

@@ -228,13 +228,7 @@ def index_foreign_keys(path):
     Ensure every foreign key column has an index on it.
     """
     db = sqlite_utils.Database(path)
-    for table_name in db.table_names():
-        table = db[table_name]
-        existing_indexes = {i.columns[0] for i in table.indexes if len(i.columns) == 1}
-        for fk in table.foreign_keys:
-            if fk.column not in existing_indexes:
-                print("Creating index on {}.{}".format(table_name, fk.column))
-                table.create_index([fk.column])
+    db.index_foreign_keys()
 
 
 @cli.command(name="create-index")

sqlite_utils/db.py

@@ -315,6 +315,16 @@ class Database:
         # can see the newly created foreign key.
         self.vacuum()
 
+    def index_foreign_keys(self):
+        for table_name in self.table_names():
+            table = self[table_name]
+            existing_indexes = {
+                i.columns[0] for i in table.indexes if len(i.columns) == 1
+            }
+            for fk in table.foreign_keys:
+                if fk.column not in existing_indexes:
+                    table.create_index([fk.column])
+
     def vacuum(self):
         self.conn.execute("VACUUM;")
 

tests/test_create.py

@@ -361,6 +361,16 @@ def test_add_foreign_key_guess_table(fresh_db):
     )
 
 
+def test_index_foreign_keys(fresh_db):
+    test_add_foreign_key_guess_table(fresh_db)
+    assert [] == fresh_db["dogs"].indexes
+    fresh_db.index_foreign_keys()
+    assert [["breed_id"]] == [i.columns for i in fresh_db["dogs"].indexes]
+    # Calling it a second time should do nothing
+    fresh_db.index_foreign_keys()
+    assert [["breed_id"]] == [i.columns for i in fresh_db["dogs"].indexes]
+
+
 @pytest.mark.parametrize(
     "extra_data,expected_new_columns",
     [