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Code Issues 32 Releases Wiki Activity

queryset-refactor: Made all the changes needed to have count() work properly

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with ValuesQuerySet. This is the general case of #2939.

At this point, all the existing tests now pass on the branch (except for
Oracle). It's a bit slower than before, though, and there are still a bunch of known bugs that aren't in the tests (or only exercised for some backends).


git-svn-id: http://code.djangoproject.com/svn/django/branches/queryset-refactor@6497 bcc190cf-cafb-0310-a4f2-bffc1f526a37
This commit is contained in:
Malcolm Tredinnick 2007-10-14 02:16:38 +00:00
parent cae24af822
commit 0ebb752e89
4 changed files with 128 additions and 55 deletions
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73
django/db/models/query.py
View File

@ -251,7 +251,7 @@ class _QuerySet(object):
##################################################
def values(self, *fields):
return self._clone(klass=ValuesQuerySet, _fields=fields)
return self._clone(klass=ValuesQuerySet, setup=True, _fields=fields)
def dates(self, field_name, kind, order='ASC'):
"""
@ -266,8 +266,8 @@ class _QuerySet(object):
field = self.model._meta.get_field(field_name, many_to_many=False)
assert isinstance(field, DateField), "%r isn't a DateField." \
% field_name
return self._clone(klass=DateQuerySet, _field=field, _kind=kind,
_order=order)
return self._clone(klass=DateQuerySet, setup=True, _field=field,
_kind=kind, _order=order)
##################################################################
# PUBLIC METHODS THAT ALTER ATTRIBUTES AND RETURN A NEW QUERYSET #
@ -363,13 +363,15 @@ class _QuerySet(object):
# PRIVATE METHODS #
###################
def _clone(self, klass=None, **kwargs):
def _clone(self, klass=None, setup=False, **kwargs):
if klass is None:
klass = self.__class__
c = klass()
c.model = self.model
c.query = self.query.clone()
c.__dict__.update(kwargs)
if setup and hasattr(c, '_setup_query'):
c._setup_query()
return c
def _get_data(self):
@ -389,16 +391,33 @@ class ValuesQuerySet(QuerySet):
# select_related isn't supported in values().
self.query.select_related = False
# QuerySet.clone() will also set up the _fields attribute with the
# names of the model fields to select.
def iterator(self):
extra_select = self.query.extra_select.keys()
extra_select.sort()
if extra_select:
self.field_names.extend([f for f in extra_select])
# Construct two objects -- fields and field_names.
# fields is a list of Field objects to fetch.
# field_names is a list of field names, which will be the keys in the
# resulting dictionaries.
for row in self.query.results_iter():
yield dict(zip(self.field_names, row))
def _setup_query(self):
"""
Sets up any special features of the query attribute.
Called by the _clone() method after initialising the rest of the
instance.
"""
# Construct two objects:
# - fields is a list of Field objects to fetch.
# - field_names is a list of field names, which will be the keys in
# the resulting dictionaries.
# 'fields' is used to configure the query, whilst field_names is stored
# in this object for use by iterator().
if self._fields:
if not extra_select:
if not self.query.extra_select:
fields = [self.model._meta.get_field(f, many_to_many=False)
for f in self._fields]
field_names = self._fields
@ -418,30 +437,42 @@ class ValuesQuerySet(QuerySet):
field_names = [f.attname for f in fields]
self.query.add_local_columns([f.column for f in fields])
if extra_select:
field_names.extend([f for f in extra_select])
self.field_names = field_names
for row in self.query.results_iter():
yield dict(zip(field_names, row))
def _clone(self, klass=None, **kwargs):
def _clone(self, klass=None, setup=False, **kwargs):
"""
Cloning a ValuesQuerySet preserves the current fields.
"""
c = super(ValuesQuerySet, self)._clone(klass, **kwargs)
c._fields = self._fields[:]
c.field_names = self.field_names[:]
if setup and hasattr(c, '_setup_query'):
c._setup_query()
return c
class DateQuerySet(QuerySet):
def iterator(self):
self.query = self.query.clone(klass=sql.DateQuery)
return self.query.results_iter()
def _setup_query(self):
"""
Sets up any special features of the query attribute.
Called by the _clone() method after initialising the rest of the
instance.
"""
self.query = self.query.clone(klass=sql.DateQuery, setup=True)
self.query.select = []
self.query.add_date_select(self._field.column, self._kind, self._order)
if self._field.null:
self.query.add_filter(('%s__isnull' % self._field.name, True))
return self.query.results_iter()
def _clone(self, klass=None, **kwargs):
c = super(DateQuerySet, self)._clone(klass, **kwargs)
def _clone(self, klass=None, setup=False, **kwargs):
c = super(DateQuerySet, self)._clone(klass, False, **kwargs)
c._field = self._field
c._kind = self._kind
if setup and hasattr(c, '_setup_query'):
c._setup_query()
return c
class EmptyQuerySet(QuerySet):
@ -455,14 +486,14 @@ class EmptyQuerySet(QuerySet):
def delete(self):
pass
def _clone(self, klass=None, **kwargs):
def _clone(self, klass=None, setup=False, **kwargs):
c = super(EmptyQuerySet, self)._clone(klass, **kwargs)
c._result_cache = []
return c
def iterator(self):
# This slightly odd construction is because we need an empty generator
# (it should raise StopIteration immediately).
# (it raises StopIteration immediately).
yield iter([]).next()
# QOperator, QAnd and QOr are temporarily retained for backwards compatibility.

10
django/db/models/sql/datastructures.py
View File

@ -32,12 +32,12 @@ class Count(Aggregate):
"""
Perform a count on the given column.
"""
def __init__(self, col=None, distinct=False):
def __init__(self, col='*', distinct=False):
"""
Set the column to count on (defaults to '*') and set whether the count
should be distinct or not.
"""
self.col = col and col or '*'
self.col = col
self.distinct = distinct
def relabel_aliases(self, change_map):
@ -49,13 +49,13 @@ class Count(Aggregate):
if not quote_func:
quote_func = lambda x: x
if isinstance(self.col, (list, tuple)):
col = '%s.%s' % tuple([quote_func(c) for c in self.col])
col = ('%s.%s' % tuple([quote_func(c) for c in self.col]))
else:
col = self.col
if self.distinct:
return 'COUNT(DISTINCT(%s))' % col
return 'COUNT(DISTINCT %s)' % col
else:
return 'COUNT(%s)' % col
return 'COUNT(%s)' % self.col
class Date(object):
"""

85
django/db/models/sql/query.py
View File

@ -147,15 +147,17 @@ class Query(object):
def get_count(self):
"""
Performs a COUNT() or COUNT(DISTINCT()) query, as appropriate, using
the current filter constraints.
Performs a COUNT() query using the current filter constraints.
"""
counter = self.clone()
counter.clear_ordering()
counter.clear_limits()
counter.select_related = False
counter.add_count_column()
data = counter.execute_sql(SINGLE)
obj = self.clone()
obj.clear_ordering()
obj.clear_limits()
obj.select_related = False
if obj.distinct and len(obj.select) > 1:
obj = self.clone(CountQuery, _query=obj, where=WhereNode(self),
distinct=False)
obj.add_count_column()
data = obj.execute_sql(SINGLE)
if not data:
return 0
number = data[0]
@ -176,7 +178,6 @@ class Query(object):
If 'with_limits' is False, any limit/offset information is not included
in the query.
"""
qn = self.connection.ops.quote_name
self.pre_sql_setup()
result = ['SELECT']
if self.distinct:
@ -185,21 +186,12 @@ class Query(object):
result.append(', '.join(out_cols))
result.append('FROM')
for alias in self.tables:
if not self.alias_map[alias][ALIAS_REFCOUNT]:
continue
name, alias, join_type, lhs, lhs_col, col = \
self.alias_map[alias][ALIAS_JOIN]
alias_str = (alias != name and ' AS %s' % alias or '')
if join_type:
result.append('%s %s%s ON (%s.%s = %s.%s)'
% (join_type, qn(name), alias_str, qn(lhs),
qn(lhs_col), qn(alias), qn(col)))
else:
result.append('%s%s' % (qn(name), alias_str))
result.extend(self.extra_tables)
from_, f_params = self.get_from_clause()
result.extend(from_)
params = list(f_params)
where, params = self.where.as_sql()
where, w_params = self.where.as_sql()
params.extend(w_params)
if where:
result.append('WHERE %s' % where)
if self.extra_where:
@ -348,6 +340,30 @@ class Query(object):
for alias, col in extra_select])
return result
def get_from_clause(self):
"""
Returns a list of strings that are joined together to go after the
"FROM" part of the query, as well as any extra parameters that need to
be included. Sub-classes, can override this to create a from-clause via
a "select", for example (e.g. CountQuery).
"""
result = []
qn = self.connection.ops.quote_name
for alias in self.tables:
if not self.alias_map[alias][ALIAS_REFCOUNT]:
continue
name, alias, join_type, lhs, lhs_col, col = \
self.alias_map[alias][ALIAS_JOIN]
alias_str = (alias != name and ' AS %s' % alias or '')
if join_type:
result.append('%s %s%s ON (%s.%s = %s.%s)'
% (join_type, qn(name), alias_str, qn(lhs),
qn(lhs_col), qn(alias), qn(col)))
else:
result.append('%s%s' % (qn(name), alias_str))
result.extend(self.extra_tables)
return result, []
def get_grouping(self):
"""
Returns a tuple representing the SQL elements in the "group by" clause.
@ -787,8 +803,17 @@ class Query(object):
if not self.distinct:
select = Count()
else:
select = Count((self.table_map[self.model._meta.db_table][0],
self.model._meta.pk.column), True)
opts = self.model._meta
if not self.select:
select = Count((self.join((None, opts.db_table, None, None)),
opts.pk.column), True)
else:
# Because of SQL portability issues, multi-column, distinct
# counts need a sub-query -- see get_count() for details.
assert len(self.select) == 1, \
"Cannot add count col with multiple cols in 'select'."
select = Count(self.select[0], True)
# Distinct handling is done in Count(), so don't do it at this
# level.
self.distinct = False
@ -987,6 +1012,16 @@ class DateQuery(Query):
else:
self.group_by = [select]
class CountQuery(Query):
"""
A CountQuery knows how to take a normal query which would select over
multiple distinct columns and turn it into SQL that can be used on a
variety of backends (it requires a select in the FROM clause).
"""
def get_from_clause(self):
result, params = self._query.as_sql()
return ['(%s) AS A1' % result], params
def find_field(name, field_list, related_query):
"""
Finds a field with a specific name in a list of field instances.

15
tests/regressiontests/queries/models.py
View File

@ -111,10 +111,17 @@ Bug #2080, #3592
>>> Author.objects.filter(Q(name='a3') | Q(item__name='one'))
[<Author: a1>, <Author: a3>]
Bug #2939
# FIXME: ValueQuerySets don't work yet.
# >>> Item.objects.values('creator').distinct().count()
# 2
Bug #1878, #2939
>>> Item.objects.values('creator').distinct().count()
3
# Create something with a duplicate 'name' so that we can test multi-column
# cases (which require some tricky SQL transformations under the covers).
>>> xx = Item(name='four', creator=a2)
>>> xx.save()
>>> Item.objects.exclude(name='two').values('creator', 'name').distinct().count()
4
>>> xx.delete()
Bug #2253
>>> q1 = Item.objects.order_by('name')