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authorRussell Keith-Magee <russell@keith-magee.com>2006-04-12 00:28:07 +0000
committerRussell Keith-Magee <russell@keith-magee.com>2006-04-12 00:28:07 +0000
commit4b3272fae8cb352b05f615453e366dadbbdbd71f (patch)
tree4f3b4fee34b443910723b37070e3097f0f0ee5cb /docs/db-api.txt
parent24541dcb73e1b28645ec6642e950b457118d8f60 (diff)
magic-removal: Reorganised and did initial revisions to db-api documentation. Still has many sections that require fleshing out.
git-svn-id: http://code.djangoproject.com/svn/django/branches/magic-removal@2679 bcc190cf-cafb-0310-a4f2-bffc1f526a37
Diffstat (limited to 'docs/db-api.txt')
-rw-r--r--docs/db-api.txt435
1 files changed, 239 insertions, 196 deletions
diff --git a/docs/db-api.txt b/docs/db-api.txt
index 732997ba22..2c89704623 100644
--- a/docs/db-api.txt
+++ b/docs/db-api.txt
@@ -10,72 +10,150 @@ models, and how to create, retrieve and update objects.
Throughout this reference, we'll refer to the following Poll application::
- class Poll(meta.Model):
- slug = meta.SlugField(unique_for_month='pub_date')
- question = meta.CharField(maxlength=255)
- pub_date = meta.DateTimeField()
- expire_date = meta.DateTimeField()
+ class Poll(models.Model):
+ slug = models.SlugField(unique_for_month='pub_date')
+ question = models.CharField(maxlength=255)
+ pub_date = models.DateTimeField()
+ expire_date = models.DateTimeField()
def __repr__(self):
return self.question
- class Choice(meta.Model):
- poll = meta.ForeignKey(Poll, edit_inline=meta.TABULAR,
+ class Choice(models.Model):
+ poll = models.ForeignKey(Poll, edit_inline=meta.TABULAR,
num_in_admin=10, min_num_in_admin=5)
- choice = meta.CharField(maxlength=255, core=True)
- votes = meta.IntegerField(editable=False, default=0)
+ choice = models.CharField(maxlength=255, core=True)
+ votes = models.IntegerField(editable=False, default=0)
def __repr__(self):
return self.choice
-Basic lookup functions
-======================
+How Queries Work
+================
-Each model exposes these module-level functions for lookups:
+Querying in Django is based upon the construction and evaluation of Query Sets.
-get_object(\**kwargs)
----------------------
+A Query Set is a representation of a query.
+
+When you compose a query using Django, you construct a Query Set; when you want
+to evaluate the query, you iterate over or slice the Query Set that represents
+your query.
+
+Every Django model has a Manager object that acts as a factory for new query sets.
+
+The manager has a special factory method for creating Suery Sets::
+
+ queryset = Poll.objects.all()
+
+This creates a new Query Set that matches all the objects of the given class.
+
+Query Set evaluation
+====================
+
+Once you have constructed a Query Set to meet your needs
+
+A Query Set is an iterable object::
+
+ queryset = Poll.objects.all()
+ for p in queryset:
+ print p
+
+Query Sets can also be sliced::
+
+ fifth_poll = queryset[4]
+ all_polls_but_the_first_two = queryset[2:]
+
+Regardless of the method used to extract data from the Query Set, upon first
+evaluation, the query will be executed on the database, and the results cached.
+Subsequent evaluations on the database will reuse the cached results.
+
+As an alternative to iteration and slicing, you can use one of the
+following functions. These functions do not populate or effect the cache:
+
+get(\**kwargs)
+--------------
Returns the object matching the given lookup parameters, which should be in
the format described in "Field lookups" below. Raises a module-level
-``*DoesNotExist`` exception if an object wasn't found for the given parameters.
+``DoesNotExist`` exception if an object wasn't found for the given parameters.
Raises ``AssertionError`` if more than one object was found.
-get_list(\**kwargs)
--------------------
+count()
+-------
-Returns a list of objects matching the given lookup parameters, which should be
-in the format described in "Field lookups" below. If no objects match the given
-parameters, it returns an empty list. ``get_list()`` will always return a list.
+Returns an integer representing the number of objects in the database matching
+the Query Set. ``count()`` never raises exceptions
-get_iterator(\**kwargs)
+Depending on which database you're using (e.g. PostgreSQL vs. MySQL), this may
+return a long integer instead of a normal Python integer.
+
+in_bulk(id_list)
+----------------
+
+Takes a list of IDs and returns a dictionary mapping each ID to an instance of
+the object with the given ID. Also takes optional keyword lookup arguments,
+which should be in the format described in "Field lookups" below. Here's an
+example, using the ``Poll`` model defined above::
+
+ >>> from datetime import datetime
+ >>> p1 = Poll(slug='whatsup', question="What's up?",
+ ... pub_date=datetime(2005, 2, 20), expire_date=datetime(2005, 3, 20))
+ >>> p1.save()
+ >>> p2 = Poll(slug='name', question="What's your name?",
+ ... pub_date=datetime(2005, 3, 20), expire_date=datetime(2005, 4, 20))
+ >>> p2.save()
+ >>> Poll.objects.all()
+ [What's up?, What's your name?]
+ >>> Poll.objects.in_bulk([1])
+ {1: What's up?}
+ >>> Poll.objects.in_bulk([1, 2])
+ {1: What's up?, 2: What's your name?}
+ >>> Poll.objects.in_bulk([])
+ {}
+
+latest(field_name=None)
-----------------------
-Just like ``get_list()``, except it returns an iterator instead of a list. This
-is more efficient for large result sets. This example shows the difference::
+Returns the latest object, according to the model's 'get_latest_by'
+option or optional given field_name.
- # get_list() loads all objects into memory.
- for obj in foos.get_list():
- print repr(obj)
+delete()
+--------
- # get_iterator() only loads a number of objects into memory at a time.
- for obj in foos.get_iterator():
- print repr(obj)
+Delete the members of the query set.
-get_count(\**kwargs)
---------------------
+Query Set construction
+======================
-Returns an integer representing the number of objects in the database matching
-the given lookup parameters, which should be in the format described in
-"Field lookups" below. ``get_count()`` never raises exceptions
+Any Query Set (evaluated or not) can be refined by calling one of the following methods:
-Depending on which database you're using (e.g. PostgreSQL vs. MySQL), this may
-return a long integer instead of a normal Python integer.
+filter(\**kwargs)
+-------------------
-get_values(\**kwargs)
+Returns a new Query Set containing objects that match the given lookup parameters.
+Lookup parameters should be in the format described in "Field lookups" below.
+
+``filter()`` will always return a list.
+
+exclude(\**kwargs)
+-------------------
+
+As for filter, but negated.
+
+distinct()
+----------
+
+If ``distinct`` is True, only distinct rows will be returned. This is equivalent
+to a ``SELECT DISTINCT`` SQL clause. You can use this with ``get_values()`` to
+get distinct values. For example, this returns the distinct first_names::
+
+ >>> people.get_values(fields=['first_name'], distinct=True)
+ [{'first_name': 'Adrian'}, {'first_name': 'Jacob'}, {'first_name': 'Simon'}]
+
+values(\*fields)
---------------------
-Just like ``get_list()``, except it returns a list of dictionaries instead of
+Just like ``filter()``, except it returns a list of dictionaries instead of
model-instance objects.
It accepts an optional parameter, ``fields``, which should be a list or tuple
@@ -86,51 +164,75 @@ field keys/values for the fields you specify. Here's an example, using the
``Poll`` model defined above::
>>> from datetime import datetime
- >>> p1 = polls.Poll(slug='whatsup', question="What's up?",
+ >>> p1 = Poll(slug='whatsup', question="What's up?",
... pub_date=datetime(2005, 2, 20), expire_date=datetime(2005, 3, 20))
>>> p1.save()
- >>> p2 = polls.Poll(slug='name', question="What's your name?",
+ >>> p2 = Poll(slug='name', question="What's your name?",
... pub_date=datetime(2005, 3, 20), expire_date=datetime(2005, 4, 20))
>>> p2.save()
- >>> polls.get_list()
+ >>> Poll.objects.all()
[What's up?, What's your name?]
- >>> polls.get_values()
+ >>> Poll.objects.get_values()
[{'id': 1, 'slug': 'whatsup', 'question': "What's up?", 'pub_date': datetime.datetime(2005, 2, 20), 'expire_date': datetime.datetime(2005, 3, 20)},
{'id': 2, 'slug': 'name', 'question': "What's your name?", 'pub_date': datetime.datetime(2005, 3, 20), 'expire_date': datetime.datetime(2005, 4, 20)}]
- >>> polls.get_values(fields=['id', 'slug'])
+ >>> Poll.objects.get_values(fields=['id', 'slug'])
[{'id': 1, 'slug': 'whatsup'}, {'id': 2, 'slug': 'name'}]
Use ``get_values()`` when you know you're only going to need a couple of field
values and you won't need the functionality of a model instance object. It's
more efficient to select only the fields you need to use.
-get_values_iterator(\**kwargs)
-------------------------------
+dates(field, kind, order='ASC')
+-------------------------------
+
+Every manager has a ``dates()`` method, which returns a list of
+``datetime.datetime`` objects representing all available dates with the given
+filters (if any) and of the given scope, as defined by the ``kind`` argument.
-Just like ``get_values()``, except it returns an iterator instead of a list.
-See the section on ``get_iterator()`` above.
+``field`` should be the name of a ``DateField`` or ``DateTimeField`` of your
+model.
-get_in_bulk(id_list, \**kwargs)
--------------------------------
+``kind`` should be either ``"year"``, ``"month"`` or ``"day"``. Each
+``datetime.datetime`` object in the result list is "truncated" to the given
+``type``.
-Takes a list of IDs and returns a dictionary mapping each ID to an instance of
-the object with the given ID. Also takes optional keyword lookup arguments,
-which should be in the format described in "Field lookups" below. Here's an
-example, using the ``Poll`` model defined above::
+ * ``"year"`` returns a list of all distinct year values for the field.
+ * ``"month"`` returns a list of all distinct year/month values for the field.
+ * ``"day"`` returns a list of all distinct year/month/day values for the field.
+
+``order``, which defaults to ``'ASC'``, should be either ``"ASC"`` or ``"DESC"``.
+This specifies how to order the results.
+
+Here's an example, using the ``Poll`` model defined above::
>>> from datetime import datetime
- >>> p1 = polls.Poll(slug='whatsup', question="What's up?",
+ >>> p1 = Poll(slug='whatsup', question="What's up?",
... pub_date=datetime(2005, 2, 20), expire_date=datetime(2005, 3, 20))
>>> p1.save()
- >>> p2 = polls.Poll(slug='name', question="What's your name?",
+ >>> p2 = Poll(slug='name', question="What's your name?",
... pub_date=datetime(2005, 3, 20), expire_date=datetime(2005, 4, 20))
>>> p2.save()
- >>> polls.get_list()
- [What's up?, What's your name?]
- >>> polls.get_in_bulk([1])
- {1: What's up?}
- >>> polls.get_in_bulk([1, 2])
- {1: What's up?, 2: What's your name?}
+ >>> Poll.objects.dates('pub_date', 'year')
+ [datetime.datetime(2005, 1, 1)]
+ >>> Poll.objects.dates('pub_date', 'month')
+ [datetime.datetime(2005, 2, 1), datetime.datetime(2005, 3, 1)]
+ >>> Poll.objects.dates('pub_date', 'day')
+ [datetime.datetime(2005, 2, 20), datetime.datetime(2005, 3, 20)]
+ >>> Poll.objects.dates('pub_date', 'day', order='DESC')
+ [datetime.datetime(2005, 3, 20), datetime.datetime(2005, 2, 20)]
+ >>> Poll.objects.filter(question__contains='name').dates('pub_date', 'day')
+ [datetime.datetime(2005, 3, 20)]
+
+
+Manager Shortcuts
+=================
+
+As a convenient shortcut, all of these Query Set functions (with the
+exception of delete) can be accessed from the Manager object itself.
+The following queries are identical::
+
+ Poll.objects.all().filter(question__startswith="What")
+ Poll.objects.filter(question__startswith="What")
Field lookups
=============
@@ -138,11 +240,11 @@ Field lookups
Basic field lookups take the form ``field__lookuptype`` (that's a
double-underscore). For example::
- polls.get_list(pub_date__lte=datetime.datetime.now())
+ Poll.objects.filter(pub_date__lte=datetime.datetime.now())
translates (roughly) into the following SQL::
- SELECT * FROM polls_polls WHERE pub_date <= NOW();
+ SELECT * FROM polls_poll WHERE pub_date <= NOW();
.. admonition:: How this is possible
@@ -155,25 +257,25 @@ The DB API supports the following lookup types:
=========== ==============================================================
Type Description
=========== ==============================================================
- exact Exact match: ``polls.get_object(id__exact=14)``.
+ exact Exact match: ``Poll.objects.get(id__exact=14)`` returns all
+ polls with an ID of exactly 14.
iexact Case-insensitive exact match:
- ``polls.get_list(slug__iexact="foo")`` matches a slug of
+ ``Poll.objects.filter(slug__iexact="foo")`` matches a slug of
``foo``, ``FOO``, ``fOo``, etc.
contains Case-sensitive containment test:
- ``polls.get_list(question__contains="spam")`` returns all polls
+ ``Poll.objects.filter(question__contains="spam")`` returns all polls
that contain "spam" in the question. (PostgreSQL and MySQL
only. SQLite doesn't support case-sensitive LIKE statements;
``contains`` will act like ``icontains`` for SQLite.)
icontains Case-insensitive containment test.
- gt Greater than: ``polls.get_list(id__gt=4)``.
+ gt Greater than: ``Poll.objects.filter(id__gt=4)``.
gte Greater than or equal to.
lt Less than.
lte Less than or equal to.
- ne Not equal to.
- in In a given list: ``polls.get_list(id__in=[1, 3, 4])`` returns
+ in In a given list: ``Poll.objects.filter(id__in=[1, 3, 4])`` returns
a list of polls whose IDs are either 1, 3 or 4.
startswith Case-sensitive starts-with:
- ``polls.get_list(question__startswith="Would")``. (PostgreSQL
+ ``Poll.objects.filter(question__startswith="Would")``. (PostgreSQL
and MySQL only. SQLite doesn't support case-sensitive LIKE
statements; ``startswith`` will act like ``istartswith`` for
SQLite.)
@@ -181,39 +283,47 @@ The DB API supports the following lookup types:
istartswith Case-insensitive starts-with.
iendswith Case-insensitive ends-with.
range Range test:
- ``polls.get_list(pub_date__range=(start_date, end_date))``
+ ``Poll.objects.filter(pub_date__range=(start_date, end_date))``
returns all polls with a pub_date between ``start_date``
and ``end_date`` (inclusive).
year For date/datetime fields, exact year match:
- ``polls.get_count(pub_date__year=2005)``.
+ ``Poll.objects.count(pub_date__year=2005)``.
month For date/datetime fields, exact month match.
day For date/datetime fields, exact day match.
isnull True/False; does is IF NULL/IF NOT NULL lookup:
- ``polls.get_list(expire_date__isnull=True)``.
+ ``Poll.objects.filter(expire_date__isnull=True)``.
=========== ==============================================================
-Multiple lookups are allowed, of course, and are translated as "AND"s::
+If no lookup type is provided, a type of ``exact`` is assumed. The following
+two statements are equivalent::
- polls.get_list(
+ Poll.objects.get(id=14)
+ Poll.objects.get(id__exact=14)
+
+Multiple lookups are also allowed. When separated by commans, the list of lookups will be
+"AND"ed together::
+
+ Poll.objects.filter(
pub_date__year=2005,
pub_date__month=1,
question__startswith="Would",
)
-...retrieves all polls published in January 2005 that have a question starting with "Would."
+...retrieves all polls published in January 2005 that have a question starting
+with "Would."
For convenience, there's a ``pk`` lookup type, which translates into
-``(primary_key)__exact``. In the polls example, these two statements are
+``(primary_key)``. In the polls example, these two statements are
equivalent::
- polls.get_object(id__exact=3)
- polls.get_object(pk=3)
+ Poll.objects.get(id__exact=3)
+ Poll.objects.get(pk=3)
``pk`` lookups also work across joins. In the polls example, these two
statements are equivalent::
- choices.get_list(poll__id__exact=3)
- choices.get_list(poll__pk=3)
+ Choice.objects.filter(poll__id=3)
+ Choice.objects.filter(poll__pk=3)
If you pass an invalid keyword argument, the function will raise ``TypeError``.
@@ -222,17 +332,19 @@ If you pass an invalid keyword argument, the function will raise ``TypeError``.
OR lookups
----------
-By default, keyword argument queries are "AND"ed together. If you have more complex query
-requirements (for example, you need to include an ``OR`` statement in your query), you need
-to use ``Q`` objects.
+By default, keyword argument queries are "AND"ed together. If you have more
+complex query requirements (for example, you need to include an ``OR``
+statement in your query), you need to use ``Q`` objects.
-A ``Q`` object is an instance of ``django.core.meta.Q``, used to encapsulate a collection of
-keyword arguments. These keyword arguments are specified in the same way as keyword arguments to
-the basic lookup functions like get_object() and get_list(). For example::
+A ``Q`` object (``django.db.models.Q``) is an object used to encapsulate a
+collection of keyword arguments. These keyword arguments are specified in
+the same way as keyword arguments to the basic lookup functions like get()
+and filter(). For example::
Q(question__startswith='What')
-``Q`` objects can be combined using the ``&`` and ``|`` operators. When an operator is used on two
+is a ``Q`` object encapsulating a single ``LIKE`` query. ``Q`` objects can be
+combined using the ``&`` and ``|`` operators. When an operator is used on two
``Q`` objects, it yields a new ``Q`` object. For example the statement::
Q(question__startswith='Who') | Q(question__startswith='What')
@@ -247,9 +359,9 @@ One or more ``Q`` objects can then provided as arguments to the lookup functions
``Q`` object arguments are provided to a lookup function, they will be "AND"ed together.
For example::
- polls.get_object(
+ Poll.objects.get(
Q(question__startswith='Who'),
- Q(pub_date__exact=date(2005, 5, 2)) | Q(pub_date__exact=date(2005, 5, 6))
+ Q(pub_date=date(2005, 5, 2)) | Q(pub_date=date(2005, 5, 6))
)
... roughly translates into the SQL::
@@ -262,25 +374,25 @@ provided to a lookup function (be they keyword argument or ``Q`` object) are "AN
However, if a ``Q`` object is provided, it must precede the definition of any keyword arguments.
For example::
- polls.get_object(
- Q(pub_date__exact=date(2005, 5, 2)) | Q(pub_date__exact=date(2005, 5, 6)),
+ Poll.objects.get(
+ Q(pub_date=date(2005, 5, 2)) | Q(pub_date=date(2005, 5, 6)),
question__startswith='Who')
... would be a valid query, equivalent to the previous example; but::
# INVALID QUERY
- polls.get_object(
+ Poll.objects.get(
question__startswith='Who',
- Q(pub_date__exact=date(2005, 5, 2)) | Q(pub_date__exact=date(2005, 5, 6)))
+ Q(pub_date=date(2005, 5, 2)) | Q(pub_date=date(2005, 5, 6)))
... would not be valid.
A ``Q`` objects can also be provided to the ``complex`` keyword argument. For example::
- polls.get_object(
+ Poll.objects.get(
complex=Q(question__startswith='Who') &
- (Q(pub_date__exact=date(2005, 5, 2)) |
- Q(pub_date__exact=date(2005, 5, 6))
+ (Q(pub_date=date(2005, 5, 2)) |
+ Q(pub_date=date(2005, 5, 6))
)
)
@@ -295,23 +407,20 @@ The results are automatically ordered by the ordering tuple given by the
``ordering`` key in the model, but the ordering may be explicitly
provided by the ``order_by`` argument to a lookup::
- polls.get_list(
- pub_date__year=2005,
- pub_date__month=1,
- order_by=('-pub_date', 'question'),
- )
+ Poll.objects.filter(pub_date__year=2005,
+ pub_date__month=1).order_by('-pub_date', 'question')
The result set above will be ordered by ``pub_date`` descending, then
by ``question`` ascending. The negative sign in front of "-pub_date" indicates
descending order. Ascending order is implied. To order randomly, use "?", like
so::
- polls.get_list(order_by=['?'])
+ Poll.objects.order_by=(['?'])
To order by a field in a different table, add the other table's name and a dot,
like so::
- choices.get_list(order_by=('polls.pub_date', 'choice'))
+ Choice.objects.all().order_by=('Poll.pub_date', 'choice')
There's no way to specify whether ordering should be case sensitive. With
respect to case-sensitivity, Django will order results however your database
@@ -321,15 +430,15 @@ Relationships (joins)
=====================
Joins may implicitly be performed by following relationships:
-``choices.get_list(poll__slug__exact="eggs")`` fetches a list of ``Choice``
+``Choice.objects.filter(poll__slug="eggs")`` fetches a list of ``Choice``
objects where the associated ``Poll`` has a slug of ``eggs``. Multiple levels
of joins are allowed.
Given an instance of an object, related objects can be looked-up directly using
convenience functions. For example, if ``p`` is a ``Poll`` instance,
-``p.get_choice_list()`` will return a list of all associated choices. Astute
+``p.choice_set.all()`` will return a list of all associated choices. Astute
readers will note that this is the same as
-``choices.get_list(poll__id__exact=p.id)``, except clearer.
+``Choice.objects.filter(poll__id=p.id)``, except clearer.
Each type of relationship creates a set of methods on each object in the
relationship. These methods are created in both directions, so objects that are
@@ -342,12 +451,12 @@ One-to-one relations
Each object in a one-to-one relationship will have a ``get_relatedobjectname()``
method. For example::
- class Place(meta.Model):
+ class Place(models.Model):
# ...
- class Restaurant(meta.Model):
+ class Restaurant(models.Model):
# ...
- the_place = meta.OneToOneField(places.Place)
+ the_place = models.OneToOneField(Place)
In the above example, each ``Place`` will have a ``get_restaurant()`` method,
and each ``Restaurant`` will have a ``get_the_place()`` method.
@@ -359,7 +468,7 @@ In each many-to-one relationship, the related object will have a
``get_relatedobject()`` method, and the related-to object will have
``get_relatedobject()``, ``get_relatedobject_list()``, and
``get_relatedobject_count()`` methods (the same as the module-level
-``get_object()``, ``get_list()``, and ``get_count()`` methods).
+``get_object()``, ``filter()``, and ``get_count()`` methods).
In the poll example above, here are the available choice methods on a ``Poll`` object ``p``::
@@ -399,50 +508,37 @@ queries, but it means that later use of relationships is much faster.
For example, using the Poll and Choice models from above, if you do the following::
- c = choices.get_object(id__exact=5, select_related=True)
+ c = Choice.objects.get(id=5, select_related=True)
Then subsequent calls to ``c.get_poll()`` won't hit the database.
Note that ``select_related`` follows foreign keys as far as possible. If you have the
following models::
- class Poll(meta.Model):
+ class Poll(models.Model):
# ...
- class Choice(meta.Model):
+ class Choice(models.Model):
# ...
- poll = meta.ForeignKey(Poll)
+ poll = models.ForeignKey(Poll)
class SingleVote(meta.Model):
# ...
- choice = meta.ForeignKey(Choice)
+ choice = models.ForeignKey(Choice)
-then a call to ``singlevotes.get_object(id__exact=4, select_related=True)`` will
+then a call to ``singlevotes.get_object(id=4, select_related=True)`` will
cache the related choice *and* the related poll::
- >>> sv = singlevotes.get_object(id__exact=4, select_related=True)
+ >>> sv = singlevotes.get_object(id=4, select_related=True)
>>> c = sv.get_choice() # Doesn't hit the database.
>>> p = c.get_poll() # Doesn't hit the database.
- >>> sv = singlevotes.get_object(id__exact=4) # Note no "select_related".
+ >>> sv = singlevotes.get_object(id=4) # Note no "select_related".
>>> c = sv.get_choice() # Hits the database.
>>> p = c.get_poll() # Hits the database.
-Limiting selected rows
-======================
-
-The ``limit``, ``offset``, and ``distinct`` keywords can be used to control
-which rows are returned. Both ``limit`` and ``offset`` should be integers which
-will be directly passed to the SQL ``LIMIT``/``OFFSET`` commands.
-
-If ``distinct`` is True, only distinct rows will be returned. This is equivalent
-to a ``SELECT DISTINCT`` SQL clause. You can use this with ``get_values()`` to
-get distinct values. For example, this returns the distinct first_names::
- >>> people.get_values(fields=['first_name'], distinct=True)
- [{'first_name': 'Adrian'}, {'first_name': 'Jacob'}, {'first_name': 'Simon'}]
-
-Other lookup options
+Extra lookup options
====================
There are a few other ways of more directly controlling the generated SQL
@@ -450,6 +546,7 @@ for the lookup. Note that by definition these extra lookups may not be
portable to different database engines (because you're explicitly writing
SQL code) and should be avoided if possible.:
+
``params``
----------
@@ -465,7 +562,7 @@ The ``select`` keyword allows you to select extra fields. This should be a
dictionary mapping attribute names to a SQL clause to use to calculate that
attribute. For example::
- polls.get_list(
+ Poll.objects.extra(
select={
'choice_count': 'SELECT COUNT(*) FROM choices WHERE poll_id = polls.id'
}
@@ -488,7 +585,8 @@ are "AND"ed to any other search criteria.
For example::
- polls.get_list(question__startswith='Who', where=['id IN (3, 4, 5, 20)'])
+ Poll.objects.filter(
+ question__startswith='Who').extra(where=['id IN (3, 4, 5, 20)'])
...translates (roughly) into the following SQL:
@@ -501,7 +599,7 @@ Once you've retrieved an object from the database using any of the above
options, changing it is extremely easy. Make changes directly to the
objects fields, then call the object's ``save()`` method::
- >>> p = polls.get_object(id__exact=15)
+ >>> p = Polls.objects.get(id__exact=15)
>>> p.slug = "new_slug"
>>> p.pub_date = datetime.datetime.now()
>>> p.save()
@@ -512,7 +610,7 @@ Creating new objects
Creating new objects (i.e. ``INSERT``) is done by creating new instances
of objects then calling save() on them::
- >>> p = polls.Poll(slug="eggs",
+ >>> p = Poll(slug="eggs",
... question="How do you like your eggs?",
... pub_date=datetime.datetime.now(),
... expire_date=some_future_date)
@@ -532,7 +630,7 @@ Related objects (e.g. ``Choices``) are created using convenience functions::
Each of those ``add_choice`` methods is equivalent to (but much simpler than)::
- >>> c = polls.Choice(poll_id=p.id, choice="Over easy", votes=0)
+ >>> c = Choice(poll_id=p.id, choice="Over easy", votes=0)
>>> c.save()
Note that when using the `add_foo()`` methods, you do not give any value
@@ -554,16 +652,7 @@ used for get_object and other query methods. For example::
>>> Polls.objects.delete(pub_date__year=2005)
-would bulk delete all Polls with a year of 2005. A bulk delete call with no
-parameters would theoretically delete all data in the table. To prevent
-accidental obliteration of a database, a bulk delete query with no parameters
-will throw an exception. If you actually want to delete all the data in a
-table, you must add a ``DELETE_ALL=True`` argument to your query.
-For example::
-
- >>> Polls.objects.delete(DELETE_ALL=True)
-
-would remove all Poll instances from the database.
+would bulk delete all Polls with a year of 2005.
Comparing objects
=================
@@ -655,14 +744,14 @@ returns an empty string.
get_FOO_size()
--------------
-For every ``FileField``, the object will have a ``get_FOO_size()`` method,
+For every ``FileField``, the object will have a ``get_FOO_filename()`` method,
where ``FOO`` is the name of the field. This returns the size of the file, in
bytes. (Behind the scenes, it uses ``os.path.getsize``.)
save_FOO_file(filename, raw_contents)
-------------------------------------
-For every ``FileField``, the object will have a ``save_FOO_file()`` method,
+For every ``FileField``, the object will have a ``get_FOO_filename()`` method,
where ``FOO`` is the name of the field. This saves the given file to the
filesystem, using the given filename. If a file with the given filename already
exists, Django adds an underscore to the end of the filename (but before the
@@ -675,49 +764,3 @@ For every ``ImageField``, the object will have ``get_FOO_height()`` and
``get_FOO_width()`` methods, where ``FOO`` is the name of the field. This
returns the height (or width) of the image, as an integer, in pixels.
-Extra module functions
-======================
-
-In addition to every function described in "Basic lookup functions" above, a
-model module might get any or all of the following methods:
-
-dates(field, kind, order='ASC')
--------------------------------
-
-Every manager has a ``dates()`` method, which returns a list of
-``datetime.datetime`` objects representing all available dates with the given
-filters (if any) and of the given scope, as defined by the ``kind`` argument.
-
-``field`` should be the name of a ``DateField`` or ``DateTimeField`` of your
-model.
-
-``kind`` should be either ``"year"``, ``"month"`` or ``"day"``. Each
-``datetime.datetime`` object in the result list is "truncated" to the given
-``type``.
-
- * ``"year"`` returns a list of all distinct year values for the field.
- * ``"month"`` returns a list of all distinct year/month values for the field.
- * ``"day"`` returns a list of all distinct year/month/day values for the field.
-
-``order``, which defaults to ``'ASC'``, should be either ``"ASC"`` or ``"DESC"``.
-This specifies how to order the results.
-
-Here's an example, using the ``Poll`` model defined above::
-
- >>> from datetime import datetime
- >>> p1 = Poll(slug='whatsup', question="What's up?",
- ... pub_date=datetime(2005, 2, 20), expire_date=datetime(2005, 3, 20))
- >>> p1.save()
- >>> p2 = Poll(slug='name', question="What's your name?",
- ... pub_date=datetime(2005, 3, 20), expire_date=datetime(2005, 4, 20))
- >>> p2.save()
- >>> Poll.objects.dates('pub_date', 'year')
- [datetime.datetime(2005, 1, 1)]
- >>> Poll.objects.dates('pub_date', 'month')
- [datetime.datetime(2005, 2, 1), datetime.datetime(2005, 3, 1)]
- >>> Poll.objects.dates('pub_date', 'day')
- [datetime.datetime(2005, 2, 20), datetime.datetime(2005, 3, 20)]
- >>> Poll.objects.dates('pub_date', 'day', order='DESC')
- [datetime.datetime(2005, 3, 20), datetime.datetime(2005, 2, 20)]
- >>> Poll.objects.filter(question__contains='name').dates('pub_date', 'day')
- [datetime.datetime(2005, 3, 20)]