fix(sqllab): execute prequeries on streaming connection to fix PostgreSQL CSV export (#40194)

Co-authored-by: Matt Fitzgerald <matt.fitzgerald@preset.io>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/unit_tests/commands/sql_lab/streaming_export_command_test.py

@@ -55,6 +55,8 @@ def mock_query():
     query.select_sql = None
     query.executed_sql = "SELECT * FROM test_table"
     query.limiting_factor = LimitingFactor.NOT_LIMITED
+    query.catalog = None
+    query.schema = "public"
     query.database = MagicMock()
     query.database.db_engine_spec = MagicMock()
     query.database.db_engine_spec.engine = "postgresql"
@@ -538,3 +540,40 @@ def test_null_values_handling(mocker, mock_query):
     assert "1,,100" in csv_data
     assert "2,test," in csv_data
     assert ",," in csv_data
+
+
+def test_catalog_and_schema_passed_to_engine(mocker, mock_query, mock_result_proxy):
+    """Test that catalog and schema are forwarded to get_sqla_engine.
+
+    Prequeries (e.g. SET search_path for PostgreSQL) are now run automatically
+    via a connect event listener registered inside get_sqla_engine, not by the
+    streaming command itself.
+    """
+    mock_query.select_sql = "SELECT * FROM test"
+    mock_query.catalog = "my_catalog"
+    mock_query.schema = "my_schema"
+
+    mock_db, mock_session = _setup_sqllab_mocks(mocker, mock_query)
+
+    mock_connection = MagicMock()
+    mock_connection.execution_options.return_value.execute.return_value = (
+        mock_result_proxy
+    )
+    mock_connection.__enter__.return_value = mock_connection
+    mock_connection.__exit__.return_value = None
+
+    mock_engine = MagicMock()
+    mock_engine.connect.return_value = mock_connection
+    mock_query.database.get_sqla_engine.return_value.__enter__.return_value = (
+        mock_engine
+    )
+
+    command = StreamingSqlResultExportCommand("test_client_123")
+    command.validate()
+
+    list(command.run()())
+
+    mock_query.database.get_sqla_engine.assert_called_once_with(
+        catalog="my_catalog",
+        schema="my_schema",
+    )