magic-removal: Fixed #1133 -- Added ability to use Q objects as args

in DB lookup queries.


git-svn-id: http://code.djangoproject.com/svn/django/branches/magic-removal@1884 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/manager.py

@@ -5,6 +5,7 @@ from django.db.models.query import Q, parse_lookup, fill_table_cache, get_cached
 from django.db.models.query import handle_legacy_orderlist, orderlist2sql, orderfield2column
 from django.dispatch import dispatcher
 from django.db.models import signals
+from django.utils.datastructures import SortedDict
 
 # Size of each "chunk" for get_iterator calls.
 # Larger values are slightly faster at the expense of more storage space.
@@ -47,7 +48,7 @@ class Manager(object):
            self.creation_counter < klass._default_manager.creation_counter:
                 klass._default_manager = self
 
-    def _get_sql_clause(self, **kwargs):
+    def _get_sql_clause(self, *args, **kwargs):
         def quote_only_if_word(word):
             if ' ' in word:
                 return word
@@ -59,12 +60,28 @@ class Manager(object):
         # Construct the fundamental parts of the query: SELECT X FROM Y WHERE Z.
         select = ["%s.%s" % (backend.quote_name(opts.db_table), backend.quote_name(f.column)) for f in opts.fields]
         tables = (kwargs.get('tables') and [quote_only_if_word(t) for t in kwargs['tables']] or [])
+        joins = SortedDict()
         where = kwargs.get('where') and kwargs['where'][:] or []
         params = kwargs.get('params') and kwargs['params'][:] or []
 
-        # Convert the kwargs into SQL.
+        # Convert all the args into SQL.
-        tables2, joins, where2, params2 = parse_lookup(kwargs.items(), opts)
+        table_count = 0
+        for arg in args:
+            # check that the provided argument is a Query (i.e., it has a get_sql method)
+            if not hasattr(arg, 'get_sql'):
+                raise TypeError, "'%s' is not a valid query argument" % str(arg)
+
+            tables2, joins2, where2, params2 = arg.get_sql(opts)
             tables.extend(tables2)
+            joins.update(joins2)
+            where.extend(where2)
+            params.extend(params2)
+
+
+        # Convert the kwargs into SQL.
+        tables2, joins2, where2, params2 = parse_lookup(kwargs.items(), opts)
+        tables.extend(tables2)
+        joins.update(joins2)
         where.extend(where2)
         params.extend(params2)
 
@@ -129,13 +146,13 @@ class Manager(object):
 
         return select, " ".join(sql), params
 
-    def get_iterator(self, **kwargs):
+    def get_iterator(self, *args, **kwargs):
         # kwargs['select'] is a dictionary, and dictionaries' key order is
         # undefined, so we convert it to a list of tuples internally.
         kwargs['select'] = kwargs.get('select', {}).items()
 
         cursor = connection.cursor()
-        select, sql, params = self._get_sql_clause(**kwargs)
+        select, sql, params = self._get_sql_clause(*args, **kwargs)
         cursor.execute("SELECT " + (kwargs.get('distinct') and "DISTINCT " or "") + ",".join(select) + sql, params)
         fill_cache = kwargs.get('select_related')
         index_end = len(self.klass._meta.fields)
@@ -152,35 +169,41 @@ class Manager(object):
                     setattr(obj, k[0], row[index_end+i])
                 yield obj
 
-    def get_list(self, **kwargs):
+    def get_list(self, *args, **kwargs):
-        return list(self.get_iterator(**kwargs))
+        return list(self.get_iterator(*args, **kwargs))
 
-    def get_count(self, **kwargs):
+    def get_count(self, *args, **kwargs):
         kwargs['order_by'] = []
         kwargs['offset'] = None
         kwargs['limit'] = None
         kwargs['select_related'] = False
-        _, sql, params = self._get_sql_clause(**kwargs)
+        _, sql, params = self._get_sql_clause(*args, **kwargs)
         cursor = connection.cursor()
         cursor.execute("SELECT COUNT(*)" + sql, params)
         return cursor.fetchone()[0]
 
-    def get_object(self, **kwargs):
+    def get_object(self, *args, **kwargs):
-        obj_list = self.get_list(**kwargs)
+        obj_list = self.get_list(*args, **kwargs)
         if len(obj_list) < 1:
             raise self.klass.DoesNotExist, "%s does not exist for %s" % (self.klass._meta.object_name, kwargs)
         assert len(obj_list) == 1, "get_object() returned more than one %s -- it returned %s! Lookup parameters were %s" % (self.klass._meta.object_name, len(obj_list), kwargs)
         return obj_list[0]
 
     def get_in_bulk(self, *args, **kwargs):
-        id_list = args and args[0] or kwargs.get('id_list', [])
+        # Separate any list arguments: the first list will be used as the id list; subsequent
-        assert id_list != [], "get_in_bulk() cannot be passed an empty list."
+        # lists will be ignored.
+        id_args = filter(lambda arg: isinstance(arg, list), args)
+        # Separate any non-list arguments: these are assumed to be query arguments
+        sql_args = filter(lambda arg: not isinstance(arg, list), args)
+
+        id_list = id_args and id_args[0] or kwargs.get('id_list', [])
+        assert id_list != [], "get_in_bulk() cannot be passed an empty ID list."        
         kwargs['where'] = ["%s.%s IN (%s)" % (backend.quote_name(self.klass._meta.db_table), backend.quote_name(self.klass._meta.pk.column), ",".join(['%s'] * len(id_list)))]
         kwargs['params'] = id_list
-        obj_list = self.get_list(**kwargs)
+        obj_list = self.get_list(*sql_args, **kwargs)
         return dict([(getattr(o, self.klass._meta.pk.attname), o) for o in obj_list])
 
-    def get_values_iterator(self, **kwargs):
+    def get_values_iterator(self, *args, **kwargs):
         # select_related and select aren't supported in get_values().
         kwargs['select_related'] = False
         kwargs['select'] = {}
@@ -192,7 +215,7 @@ class Manager(object):
             fields = [f.column for f in self.klass._meta.fields]
 
         cursor = connection.cursor()
-        _, sql, params = self._get_sql_clause(**kwargs)
+        _, sql, params = self._get_sql_clause(*args, **kwargs)
         select = ['%s.%s' % (backend.quote_name(self.klass._meta.db_table), backend.quote_name(f)) for f in fields]
         cursor.execute("SELECT " + (kwargs.get('distinct') and "DISTINCT " or "") + ",".join(select) + sql, params)
         while 1:
@@ -202,17 +225,22 @@ class Manager(object):
             for row in rows:
                 yield dict(zip(fields, row))
 
-    def get_values(self, **kwargs):
+    def get_values(self, *args, **kwargs):
-        return list(self.get_values_iterator(**kwargs))
+        return list(self.get_values_iterator(*args, **kwargs))
 
-    def __get_latest(self, **kwargs):
+    def __get_latest(self, *args, **kwargs):
         kwargs['order_by'] = ('-' + self.klass._meta.get_latest_by,)
         kwargs['limit'] = 1
-        return self.get_object(**kwargs)
+        return self.get_object(*args, **kwargs)
 
     def __get_date_list(self, field, *args, **kwargs):
+        # Separate any string arguments: the first will be used as the kind
+        kind_args = filter(lambda arg: isinstance(arg, str), args)
+        # Separate any non-list arguments: these are assumed to be query arguments
+        sql_args = filter(lambda arg: not isinstance(arg, str), args)
+        
         from django.db.backends.util import typecast_timestamp
-        kind = args and args[0] or kwargs['kind']
+        kind = kind_args and kind_args[0] or kwargs.get(['kind'],"")
         assert kind in ("month", "year", "day"), "'kind' must be one of 'year', 'month' or 'day'."
         order = 'ASC'
         if kwargs.has_key('order'):
@@ -223,7 +251,7 @@ class Manager(object):
         if field.null:
             kwargs.setdefault('where', []).append('%s.%s IS NOT NULL' % \
                 (backend.quote_name(self.klass._meta.db_table), backend.quote_name(field.column)))
-        select, sql, params = self._get_sql_clause(**kwargs)
+        select, sql, params = self._get_sql_clause(*sql_args, **kwargs)
         sql = 'SELECT %s %s GROUP BY 1 ORDER BY 1 %s' % \
             (backend.get_date_trunc_sql(kind, '%s.%s' % (backend.quote_name(self.klass._meta.db_table),
             backend.quote_name(field.column))), sql, order)

django/db/models/query.py

@@ -198,6 +198,8 @@ def parse_lookup(kwarg_items, opts):
         elif value is None:
             pass
         elif kwarg == 'complex':
+            if not hasattr(value, 'get_sql'):
+                raise TypeError, "'%s' is not a valid query argument" % str(arg)
             tables2, joins2, where2, params2 = value.get_sql(opts)
             tables.extend(tables2)
             joins.update(joins2)

docs/db-api.txt

@@ -224,32 +224,67 @@ OR lookups
 
 **New in Django development version.**
 
-By default, multiple lookups are "AND"ed together. If you'd like to use ``OR``
+By default, keyword argument queries are "AND"ed together. If you have more complex query 
-statements in your queries, use the ``complex`` lookup type.
+requirements (for example, you need to include an ``OR`` statement in your query), you need 
+to use ``Q`` objects.
 
-``complex`` takes an expression of clauses, each of which is an instance of
+A ``Q`` object is an instance of ``django.core.meta.Q``, used to encapsulate a collection of 
-``django.core.meta.Q``. ``Q`` takes an arbitrary number of keyword arguments in
+keyword arguments. These keyword arguments are specified in the same way as keyword arguments to
-the standard Django lookup format. And you can use Python's "and" (``&``) and
+the basic lookup functions like get_object() and get_list(). For example::
-"or" (``|``) operators to combine ``Q`` instances. For example::
 
-    from django.core.meta import Q
+    Q(question__startswith='What')
-    polls.get_object(complex=(Q(question__startswith='Who') | Q(question__startswith='What')))
 
-The ``|`` symbol signifies an "OR", so this (roughly) translates into::
+``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::
 
-    SELECT * FROM polls
+    Q(question__startswith='Who') | Q(question__startswith='What')
-    WHERE question LIKE 'Who%' OR question LIKE 'What%';
 
-You can use ``&`` and ``|`` operators together, and use parenthetical grouping.
+... yields a single ``Q`` object that represents the "OR" of two "question__startswith" queries, equivalent to the SQL WHERE clause::
-Example::
 
-    polls.get_object(complex=(Q(question__startswith='Who') & (Q(pub_date__exact=date(2005, 5, 2)) | Q(pub_date__exact=date(2005, 5, 6))))
+    ... WHERE question LIKE 'Who%' OR question LIKE 'What%'
 
-This roughly translates into::
+You can compose statements of arbitrary complexity by combining ``Q`` objects with the ``&`` and ``|`` operators. Parenthetical grouping can also be used. 
 
-    SELECT * FROM polls
+One or more ``Q`` objects can then provided as arguments to the lookup functions. If multiple 
-    WHERE question LIKE 'Who%'
+``Q`` object arguments are provided to a lookup function, they will be "AND"ed together. 
-        AND (pub_date = '2005-05-02' OR pub_date = '2005-05-06');
+For example::
+
+    polls.get_object(
+        Q(question__startswith='Who'), 
+        Q(pub_date__exact=date(2005, 5, 2)) | Q(pub_date__exact=date(2005, 5, 6))
+    )
+
+... roughly translates into the SQL::
+
+    SELECT * from polls WHERE question LIKE 'Who%'
+        AND (pub_date = '2005-05-02' OR pub_date = '2005-05-06')
+
+If necessary, lookup functions can mix the use of ``Q`` objects and keyword arguments. All arguments
+provided to a lookup function (be they keyword argument or ``Q`` object) are "AND"ed together. 
+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)),
+        question__startswith='Who')
+
+... would be a valid query, equivalent to the previous example; but::
+
+    # INVALID QUERY
+    polls.get_object(
+        question__startswith='Who', 
+        Q(pub_date__exact=date(2005, 5, 2)) | Q(pub_date__exact=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(
+        complex=Q(question__startswith='Who') & 
+            (Q(pub_date__exact=date(2005, 5, 2)) | 
+             Q(pub_date__exact=date(2005, 5, 6))
+        )
+    )
 
 See the `OR lookups examples page`_ for more examples.
 

tests/modeltests/lookup/models.py

@@ -68,7 +68,7 @@ Article 4
 >>> Article.objects.get_in_bulk([])
 Traceback (most recent call last):
     ...
-AssertionError: get_in_bulk() cannot be passed an empty list.
+AssertionError: get_in_bulk() cannot be passed an empty ID list.
 
 # get_values() is just like get_list(), except it returns a list of
 # dictionaries instead of object instances -- and you can specify which fields

tests/modeltests/or_lookups/models.py

@@ -3,7 +3,7 @@
 
 To perform an OR lookup, or a lookup that combines ANDs and ORs, use the
 ``complex`` keyword argument, and pass it an expression of clauses using the
-variable ``django.db.models.Q``.
+variable ``django.db.models.Q`` (or any object with a get_sql method).
 """
 
 from django.db import models
@@ -54,4 +54,33 @@ API_TESTS = """
 >>> Article.objects.get_list(complex=(Q(pk=1) | Q(pk=2) | Q(pk=3)))
 [Hello, Goodbye, Hello and goodbye]
 
+# Queries can use Q objects as args
+>>> Article.objects.get_list(Q(headline__startswith='Hello'))
+[Hello, Hello and goodbye]
+
+# Q arg objects are ANDed 
+>>> Article.objects.get_list(Q(headline__startswith='Hello'), Q(headline__contains='bye'))
+[Hello and goodbye]
+
+# Q arg AND order is irrelevant
+>>> Article.objects.get_list(Q(headline__contains='bye'), headline__startswith='Hello')
+[Hello and goodbye]
+
+# QOrs are ok, as they ultimately resolve to a Q 
+>>> Article.objects.get_list(Q(headline__contains='Hello') | Q(headline__contains='bye'))
+[Hello, Goodbye, Hello and goodbye]
+
+# Try some arg queries with operations other than get_list
+>>> Article.objects.get_object(Q(headline__startswith='Hello'), Q(headline__contains='bye'))
+Hello and goodbye
+
+>>> Article.objects.get_count(Q(headline__startswith='Hello') | Q(headline__contains='bye'))
+3
+
+>>> Article.objects.get_values(Q(headline__startswith='Hello'), Q(headline__contains='bye'))
+[{'headline': 'Hello and goodbye', 'pub_date': datetime.datetime(2005, 11, 29, 0, 0), 'id': 3}]
+
+>>> Article.objects.get_in_bulk([1,2], Q(headline__startswith='Hello'))
+{1: Hello}
+
 """