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+++ b/parts/django/docs/faq/models.txt	Sat Jan 08 11:20:57 2011 +0530
@@ -0,0 +1,105 @@
+FAQ: Databases and models
+=========================
+
+.. _faq-see-raw-sql-queries:
+
+How can I see the raw SQL queries Django is running?
+----------------------------------------------------
+
+Make sure your Django ``DEBUG`` setting is set to ``True``. Then, just do
+this::
+
+    >>> from django.db import connection
+    >>> connection.queries
+    [{'sql': 'SELECT polls_polls.id,polls_polls.question,polls_polls.pub_date FROM polls_polls',
+    'time': '0.002'}]
+
+``connection.queries`` is only available if ``DEBUG`` is ``True``. It's a list
+of dictionaries in order of query execution. Each dictionary has the following::
+
+    ``sql`` -- The raw SQL statement
+    ``time`` -- How long the statement took to execute, in seconds.
+
+``connection.queries`` includes all SQL statements -- INSERTs, UPDATES,
+SELECTs, etc. Each time your app hits the database, the query will be recorded.
+Note that the raw SQL logged in ``connection.queries`` may not include
+parameter quoting.  Parameter quoting is performed by the database-specific
+backend, and not all backends provide a way to retrieve the SQL after quoting.
+
+.. versionadded:: 1.2
+
+If you are using :doc:`multiple databases</topics/db/multi-db>`, you can use the
+same interface on each member of the ``connections`` dictionary::
+
+    >>> from django.db import connections
+    >>> connections['my_db_alias'].queries
+
+Can I use Django with a pre-existing database?
+----------------------------------------------
+
+Yes. See :doc:`Integrating with a legacy database </howto/legacy-databases>`.
+
+If I make changes to a model, how do I update the database?
+-----------------------------------------------------------
+
+If you don't mind clearing data, your project's ``manage.py`` utility has an
+option to reset the SQL for a particular application::
+
+    manage.py reset appname
+
+This drops any tables associated with ``appname`` and recreates them.
+
+If you do care about deleting data, you'll have to execute the ``ALTER TABLE``
+statements manually in your database. That's the way we've always done it,
+because dealing with data is a very sensitive operation that we've wanted to
+avoid automating. That said, there's some work being done to add partially
+automated database-upgrade functionality.
+
+Do Django models support multiple-column primary keys?
+------------------------------------------------------
+
+No. Only single-column primary keys are supported.
+
+But this isn't an issue in practice, because there's nothing stopping you from
+adding other constraints (using the ``unique_together`` model option or
+creating the constraint directly in your database), and enforcing the
+uniqueness at that level. Single-column primary keys are needed for things such
+as the admin interface to work; e.g., you need a simple way of being able to
+specify an object to edit or delete.
+
+How do I add database-specific options to my CREATE TABLE statements, such as specifying MyISAM as the table type?
+------------------------------------------------------------------------------------------------------------------
+
+We try to avoid adding special cases in the Django code to accommodate all the
+database-specific options such as table type, etc. If you'd like to use any of
+these options, create an :ref:`SQL initial data file <initial-sql>` that
+contains ``ALTER TABLE`` statements that do what you want to do. The initial
+data files are executed in your database after the ``CREATE TABLE`` statements.
+
+For example, if you're using MySQL and want your tables to use the MyISAM table
+type, create an initial data file and put something like this in it::
+
+    ALTER TABLE myapp_mytable ENGINE=MyISAM;
+
+As explained in the :ref:`SQL initial data file <initial-sql>` documentation,
+this SQL file can contain arbitrary SQL, so you can make any sorts of changes
+you need to make.
+
+Why is Django leaking memory?
+-----------------------------
+
+Django isn't known to leak memory. If you find your Django processes are
+allocating more and more memory, with no sign of releasing it, check to make
+sure your ``DEBUG`` setting is set to ``False``. If ``DEBUG`` is ``True``, then
+Django saves a copy of every SQL statement it has executed.
+
+(The queries are saved in ``django.db.connection.queries``. See
+`How can I see the raw SQL queries Django is running?`_.)
+
+To fix the problem, set ``DEBUG`` to ``False``.
+
+If you need to clear the query list manually at any point in your functions,
+just call ``reset_queries()``, like this::
+
+    from django import db
+    db.reset_queries()