fix: handle closed DuckDB connections gracefully (#7111) (#7114)

Fixes #7111 where closed DuckDB connections would trigger error logging
when marimo attempts to query them for database information.

Author: mscolnick

marimo/_data/get_datasets.py

@@ -98,7 +98,15 @@ def execute_duckdb_query(
             return duckdb.execute(query).fetchall()
 
         return connection.execute(query).fetchall()
-    except Exception:
+    except Exception as e:
+        if DependencyManager.duckdb.has():
+            import duckdb
+
+            # Connection is closed, return empty result
+            if isinstance(e, duckdb.ConnectionException):
+                LOGGER.debug("Skipping query on closed DuckDB connection")
+                return []
+
         LOGGER.exception("Failed to execute DuckDB query %s", query)
         return []
 
@@ -156,6 +164,14 @@ def _get_databases_from_duckdb_internal(
         if DependencyManager.duckdb.has():
             import duckdb
 
+            # Connection is closed, skip gracefully
+            if isinstance(e, duckdb.ConnectionException):
+                LOGGER.debug(
+                    "Skipping closed DuckDB connection for engine %s",
+                    engine_name,
+                )
+                return []
+
             # Certain ducklakes don't support SHOW ALL TABLES
             if isinstance(e, duckdb.NotImplementedException):
                 return get_duckdb_databases_agg_query(connection, engine_name)
@@ -424,7 +440,15 @@ def _get_duckdb_database_names(
             if not internal:
                 database_names.append(database_name)
         return database_names
-    except Exception:
+    except Exception as e:
+        if DependencyManager.duckdb.has():
+            import duckdb
+
+            # Connection is closed, skip gracefully
+            if isinstance(e, duckdb.ConnectionException):
+                LOGGER.debug("Skipping closed DuckDB connection")
+                return []
+
         LOGGER.debug("Failed to get database names from DuckDB")
         return []
 

tests/_data/test_get_datasets.py

@@ -571,3 +571,44 @@ def test_get_databases_agg_query() -> None:
     ]
 
     connection.execute(cleanup_query)
+
+
+@pytest.mark.skipif(not HAS_DEPS, reason="optional dependencies not installed")
+def test_get_databases_with_closed_connection() -> None:
+    """Test that closed connections are handled gracefully without errors."""
+    import duckdb
+
+    # Create a connection, add tables, then close it
+    connection = duckdb.connect(":memory:")
+    connection.execute("CREATE TABLE test_table (id INTEGER, name VARCHAR)")
+    connection.close()
+
+    # This should not raise an exception
+    result = get_databases_from_duckdb(
+        connection=connection, engine_name=VariableName("closed_engine")
+    )
+
+    # Should return empty list for closed connection
+    assert result == []
+
+
+@pytest.mark.skipif(not HAS_DEPS, reason="optional dependencies not installed")
+def test_get_databases_with_context_manager_closed_connection() -> None:
+    """Test that connections closed via context manager are handled gracefully."""
+    import duckdb
+
+    # Use context manager to automatically close connection
+    with duckdb.connect(":memory:") as connection:
+        connection.execute(
+            "CREATE TABLE test_table (id INTEGER, name VARCHAR)"
+        )
+        # Store reference to connection
+        closed_conn = connection
+
+    # Connection is now closed, this should not raise an exception
+    result = get_databases_from_duckdb(
+        connection=closed_conn, engine_name=VariableName("closed_engine")
+    )
+
+    # Should return empty list for closed connection
+    assert result == []