rarely needed:

* When creating a database object by calling the constructor directly,

  it must explicitly be added to the session.

* When creating an object using a factory function (like

  ``create_repo``), the returned object has already (by convention)

  been added to the session, and should not be added again.

* When getting an object from the session (via ``Session().query`` or

  any of the utility functions that look up objects in the database),

  it's already part of the session, and should not be added again.

  SQLAlchemy monitors attribute modifications automatically for all

  objects it knows about and syncs them to the database.

SQLAlchemy also flushes changes to the database automatically; manually

calling ``Session().flush`` is usually only necessary when the Python

code needs the database to assign an "auto-increment" primary key ID to

a freshly created model object (before flushing, the ID attribute will

be ``None``).

Debugging

^^^^^^^^^

``DEBUG`` or ``INFO`` level, especially ``[logger_kallithea]``, but perhaps

also other loggers. It is often easier to add additional ``log`` or ``print``

statements than to use a Python debugger.

Sometimes it is simpler to disable ``errorpage.enabled`` and perhaps also

``trace_errors.enable`` to expose raw errors instead of adding extra

processing. Enabling ``debug`` can be helpful for showing and exploring

tracebacks in the browser, but is also insecure and will add extra processing.

TurboGears2 DebugBar

^^^^^^^^^^^^^^^^^^^^

It is possible to enable the TurboGears2-provided DebugBar_, a toolbar overlayed

over the Kallithea web interface, allowing you to see:

* timing information of the current request, including profiling information

* request data, including GET data, POST data, cookies, headers and environment

  variables

* a list of executed database queries, including timing and result values

DebugBar is only activated when ``debug = true`` is set in the configuration

file. This is important, because the DebugBar toolbar will be visible for all

users, and allow them to see information they should not be allowed to see. Like

is anyway the case for ``debug = true``, do not use this in production!