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django/django/db/models/query.py

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from django.db import backend, connection
from django.db.models.fields import FieldDoesNotExist
from django.utils.datastructures import SortedDict
import copy
LOOKUP_SEPARATOR = '__'
# Size of each "chunk" for get_iterator calls.
# Larger values are slightly faster at the expense of more storage space.
GET_ITERATOR_CHUNK_SIZE = 100
####################
# HELPER FUNCTIONS #
####################
# Django currently supports two forms of ordering.
# Form 1 (deprecated) example:
# order_by=(('pub_date', 'DESC'), ('headline', 'ASC'), (None, 'RANDOM'))
# Form 2 (new-style) example:
# order_by=('-pub_date', 'headline', '?')
# Form 1 is deprecated and will no longer be supported for Django's first
# official release. The following code converts from Form 1 to Form 2.
LEGACY_ORDERING_MAPPING = {'ASC': '_', 'DESC': '-_', 'RANDOM': '?'}
def handle_legacy_orderlist(order_list):
if not order_list or isinstance(order_list[0], basestring):
return order_list
else:
import warnings
new_order_list = [LEGACY_ORDERING_MAPPING[j.upper()].replace('_', str(i)) for i, j in order_list]
warnings.warn("%r ordering syntax is deprecated. Use %r instead." % (order_list, new_order_list), DeprecationWarning)
return new_order_list
def orderfield2column(f, opts):
try:
return opts.get_field(f, False).column
except FieldDoesNotExist:
return f
def orderlist2sql(order_list, opts, prefix=''):
if prefix.endswith('.'):
prefix = backend.quote_name(prefix[:-1]) + '.'
output = []
for f in handle_legacy_orderlist(order_list):
if f.startswith('-'):
output.append('%s%s DESC' % (prefix, backend.quote_name(orderfield2column(f[1:], opts))))
elif f == '?':
output.append(backend.get_random_function_sql())
else:
output.append('%s%s ASC' % (prefix, backend.quote_name(orderfield2column(f, opts))))
return ', '.join(output)
def quote_only_if_word(word):
if ' ' in word:
return word
else:
return backend.quote_name(word)
class QuerySet(object):
"Represents a lazy database lookup for a set of objects"
# Subclasses need to provide 'self.klass' attribute for this class
# to be able to function.
# Dictionary of lookup parameters to apply to every _get_sql_clause().
core_filters = {}
def __init__(self):
self._filters = self.core_filters.copy()
self._order_by = () # Ordering, e.g. ('date', '-name')
self._select_related = False # Whether to fill cache for related objects.
self._distinct = False # Whether the query should use SELECT DISTINCT.
# self._result_cache = None
self._select = None # Dictionary of attname -> SQL.
self._where = None # List of extra WHERE clauses to use.
self._params = None # List of params to use for extra WHERE clauses.
self._tables = None # List of extra tables to use.
self._offset = None # OFFSET clause
self._limit = None # LIMIT clause
# self._use_cache = False
########################
# PYTHON MAGIC METHODS #
########################
# def __len__(self):
# return len(list(self))
###########################################
# PUBLIC METHODS THAT DO DATABASE QUERIES #
###########################################
def __iter__(self):
"Performs the SELECT database lookup of this QuerySet."
# self._select is a dictionary, and dictionaries' key order is
# undefined, so we convert it to a list of tuples.
extra_select = (self._select or {}).items()
cursor = connection.cursor()
select, sql, params = self._get_sql_clause(True)
cursor.execute("SELECT " + (self._distinct and "DISTINCT " or "") + ",".join(select) + sql, params)
fill_cache = self._select_related
index_end = len(self.klass._meta.fields)
while 1:
rows = cursor.fetchmany(GET_ITERATOR_CHUNK_SIZE)
if not rows:
raise StopIteration
for row in rows:
if fill_cache:
obj, index_end = get_cached_row(self.klass, row, 0)
else:
obj = self.klass(*row[:index_end])
for i, k in enumerate(extra_select):
setattr(obj, k[0], row[index_end+i])
yield obj
def count(self):
"Performs a SELECT COUNT() and returns the number of records as an integer."
counter = self._clone()
counter._order_by = []
counter._offset = None
counter._limit = None
counter._select_related = False
_, sql, params = counter._get_sql_clause(True)
cursor = connection.cursor()
cursor.execute("SELECT COUNT(*)" + sql, params)
return cursor.fetchone()[0]
def get(self, **kwargs):
"Performs the SELECT and returns a single object matching the given keyword arguments."
obj_list = list(self.filter(**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() 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]
#############################################
# PUBLIC METHODS THAT RETURN A NEW QUERYSET #
#############################################
def filter(self, **kwargs):
"Returns a new QuerySet instance with the args ANDed to the existing set."
clone = self._clone()
clone._filters.update(**kwargs)
return clone
def select_related(self, true_or_false=True):
"Returns a new QuerySet instance with '_select_related' modified."
return self._clone(_select_related=true_or_false)
def order_by(self, *field_names):
"Returns a new QuerySet instance with the ordering changed."
return self._clone(_order_by=field_names)
def distinct(self, true_or_false=True):
"Returns a new QuerySet instance with '_distinct' modified."
return self._clone(_distinct=true_or_false)
###################
# PRIVATE METHODS #
###################
def _clone(self, **kwargs):
c = QuerySet()
c._filters = self._filters.copy()
c._order_by = self._order_by
c._select_related = self._select_related
c._distinct = self._distinct
c._select = self._select
c._offset = self._offset
c._limit = self._limit
return c
def _get_sql_clause(self, allow_joins):
opts = self.klass._meta
# 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 = [quote_only_if_word(t) for t in (self._tables or [])]
joins = SortedDict()
where = self._where or []
params = self._params or []
# Convert self._filters into SQL.
tables2, joins2, where2, params2 = parse_lookup(self._filters.items(), opts)
tables.extend(tables2)
joins.update(joins2)
where.extend(where2)
params.extend(params2)
# Add additional tables and WHERE clauses based on select_related.
if self._select_related:
fill_table_cache(opts, select, tables, where, opts.db_table, [opts.db_table])
# Add any additional SELECTs.
if self._select:
select.extend(['(%s) AS %s' % (quote_only_if_word(s[1]), backend.quote_name(s[0])) for s in self._select])
# Start composing the body of the SQL statement.
sql = [" FROM", backend.quote_name(opts.db_table)]
# Check if extra tables are allowed. If not, throw an error
if (tables or joins) and not allow_joins:
raise TypeError, "Joins are not allowed in this type of query"
# Compose the join dictionary into SQL describing the joins.
if joins:
sql.append(" ".join(["%s %s AS %s ON %s" % (join_type, table, alias, condition)
for (alias, (table, join_type, condition)) in joins.items()]))
# Compose the tables clause into SQL.
if tables:
sql.append(", " + ", ".join(tables))
# Compose the where clause into SQL.
if where:
sql.append(where and "WHERE " + " AND ".join(where))
# ORDER BY clause
order_by = []
for f in handle_legacy_orderlist(self._order_by or opts.ordering):
if f == '?': # Special case.
order_by.append(backend.get_random_function_sql())
else:
if f.startswith('-'):
col_name = f[1:]
order = "DESC"
else:
col_name = f
order = "ASC"
if "." in col_name:
table_prefix, col_name = col_name.split('.', 1)
table_prefix = backend.quote_name(table_prefix) + '.'
else:
# Use the database table as a column prefix if it wasn't given,
# and if the requested column isn't a custom SELECT.
if "." not in col_name and col_name not in [k[0] for k in (self._select or ())]:
table_prefix = backend.quote_name(opts.db_table) + '.'
else:
table_prefix = ''
order_by.append('%s%s %s' % (table_prefix, backend.quote_name(orderfield2column(col_name, opts)), order))
if order_by:
sql.append("ORDER BY " + ", ".join(order_by))
# LIMIT and OFFSET clauses
if self._limit is not None:
sql.append("%s " % backend.get_limit_offset_sql(self._limit, self._offset))
else:
assert self._offset is None, "'offset' is not allowed without 'limit'"
return select, " ".join(sql), params
# class QuerySet(object):
# def _ensure_compatible(self, other):
# if self._distinct != other._distinct:
# raise ValueException, "Can't combine a unique query with a non-unique query"
#
# def _combine(self, other):
# self._ensure_compatible(other)
# # get a deepcopy of 'other's order by
# # (so that A.filter(args1) & A.filter(args2) does the same as
# # A.filter(args1).filter(args2)
# combined = other._clone()
# # If 'self' is ordered and 'other' isn't, propagate 'self's ordering
# if len(self._order_by) > 0 and len(combined._order_by == 0):
# combined._order_by = copy.deepcopy(self._order_by)
# return combined
#
# def extras(self, params=None, select=None, where=None, tables=None):
# return self._clone(_params=params, _select=select, _where=where, _tables=tables)
#
# def __and__(self, other):
# combined = self._combine(other)
# combined._filter = self._filter & other._filter
# return combined
#
# def __or__(self, other):
# combined = self._combine(other)
# combined._filter = self._filter | other._filter
# return combined
#
# def _fetch_data(self):
# if self._use_cache:
# if self._result_cache is None:
# self._result_cache = list(self.get_iterator())
# return self._result_cache
# else:
# return list(self.get_iterator())
#
# def __getitem__(self, k):
# """Retrieve an item or slice from the set of results"""
# # getitem can't return query instances, because .filter()
# # and .order_by() methods on the result would break badly.
# # This means we don't have to worry about arithmetic with
# # self._limit or self._offset - they will both be None
# # at this point
# if isinstance(k, slice):
# # Get a new query if we haven't already got data from db
# if self._result_cache is None:
# # slice.stop and slice.start
# clone = self._clone(_offset=k.start, _limit=k.stop)
# return list(clone)[::k.step]
# # TODO - we are throwing away this retrieved data.
# # We could cache it if we had some kind of sparse
# # list structure we could put it in.
# else:
# return self._result_cache[k]
#
# else:
# # TODO: possibly use a new query which just gets one item
# # if we haven't already got them all?
# return self._fetch_data()[k]
class QOperator:
"Base class for QAnd and QOr"
def __init__(self, *args):
self.args = args
def get_sql(self, opts):
tables, joins, where, params = [], {}, [], []
for val in self.args:
tables2, joins2, where2, params2 = val.get_sql(opts)
tables.extend(tables2)
joins.update(joins2)
where.extend(where2)
params.extend(params2)
return tables, joins, ['(%s)' % self.operator.join(where)], params
class QAnd(QOperator):
"Encapsulates a combined query that uses 'AND'."
operator = ' AND '
def __or__(self, other):
return QOr(self, other)
def __and__(self, other):
if isinstance(other, QAnd):
return QAnd(*(self.args+other.args))
elif isinstance(other, (Q, QOr)):
return QAnd(*(self.args+(other,)))
else:
raise TypeError, other
class QOr(QOperator):
"Encapsulates a combined query that uses 'OR'."
operator = ' OR '
def __and__(self, other):
return QAnd(self, other)
def __or__(self, other):
if isinstance(other, QOr):
return QOr(*(self.args+other.args))
elif isinstance(other, (Q, QAnd)):
return QOr(*(self.args+(other,)))
else:
raise TypeError, other
class Q:
"Encapsulates queries as objects that can be combined logically."
def __init__(self, **kwargs):
self.kwargs = kwargs
def __and__(self, other):
return QAnd(self, other)
def __or__(self, other):
return QOr(self, other)
def get_sql(self, opts):
return parse_lookup(self.kwargs.items(), opts)
def get_where_clause(lookup_type, table_prefix, field_name, value):
if table_prefix.endswith('.'):
table_prefix = backend.quote_name(table_prefix[:-1])+'.'
field_name = backend.quote_name(field_name)
try:
return '%s%s %s' % (table_prefix, field_name, (backend.OPERATOR_MAPPING[lookup_type] % '%s'))
except KeyError:
pass
if lookup_type == 'in':
return '%s%s IN (%s)' % (table_prefix, field_name, ','.join(['%s' for v in value]))
elif lookup_type in ('range', 'year'):
return '%s%s BETWEEN %%s AND %%s' % (table_prefix, field_name)
elif lookup_type in ('month', 'day'):
return "%s = %%s" % backend.get_date_extract_sql(lookup_type, table_prefix + field_name)
elif lookup_type == 'isnull':
return "%s%s IS %sNULL" % (table_prefix, field_name, (not value and 'NOT ' or ''))
raise TypeError, "Got invalid lookup_type: %s" % repr(lookup_type)
def get_cached_row(klass, row, index_start):
"Helper function that recursively returns an object with cache filled"
index_end = index_start + len(klass._meta.fields)
obj = klass(*row[index_start:index_end])
for f in klass._meta.fields:
if f.rel and not f.null:
rel_obj, index_end = get_cached_row(f.rel.to, row, index_end)
setattr(obj, f.get_cache_name(), rel_obj)
return obj, index_end
def fill_table_cache(opts, select, tables, where, old_prefix, cache_tables_seen):
"""
Helper function that recursively populates the select, tables and where (in
place) for fill-cache queries.
"""
for f in opts.fields:
if f.rel and not f.null:
db_table = f.rel.to._meta.db_table
if db_table not in cache_tables_seen:
tables.append(backend.quote_name(db_table))
else: # The table was already seen, so give it a table alias.
new_prefix = '%s%s' % (db_table, len(cache_tables_seen))
tables.append('%s %s' % (backend.quote_name(db_table), backend.quote_name(new_prefix)))
db_table = new_prefix
cache_tables_seen.append(db_table)
where.append('%s.%s = %s.%s' % \
(backend.quote_name(old_prefix), backend.quote_name(f.column),
backend.quote_name(db_table), backend.quote_name(f.rel.get_related_field().column)))
select.extend(['%s.%s' % (backend.quote_name(db_table), backend.quote_name(f2.column)) for f2 in f.rel.to._meta.fields])
fill_table_cache(f.rel.to._meta, select, tables, where, db_table, cache_tables_seen)
def parse_lookup(kwarg_items, opts):
# Helper function that handles converting API kwargs
# (e.g. "name__exact": "tom") to SQL.
# 'joins' is a sorted dictionary describing the tables that must be joined
# to complete the query. The dictionary is sorted because creation order
# is significant; it is a dictionary to ensure uniqueness of alias names.
#
# Each key-value pair follows the form
# alias: (table, join_type, condition)
# where
# alias is the AS alias for the joined table
# table is the actual table name to be joined
# join_type is the type of join (INNER JOIN, LEFT OUTER JOIN, etc)
# condition is the where-like statement over which narrows the join.
# alias will be derived from the lookup list name.
#
# At present, this method only every returns INNER JOINs; the option is
# there for others to implement custom Q()s, etc that return other join
# types.
tables, joins, where, params = [], SortedDict(), [], []
for kwarg, value in kwarg_items:
if value is None:
pass
else:
path = kwarg.split(LOOKUP_SEPARATOR)
# Extract the last elements of the kwarg.
# The very-last is the clause (equals, like, etc).
# The second-last is the table column on which the clause is
# to be performed.
# The exceptions to this are:
# 1) "pk", which is an implicit id__exact;
# if we find "pk", make the clause "exact', and insert
# a dummy name of None, which we will replace when
# we know which table column to grab as the primary key.
# 2) If there is only one part, assume it to be an __exact
clause = path.pop()
if clause == 'pk':
clause = 'exact'
path.append(None)
elif len(path) == 0:
path.append(clause)
clause = 'exact'
if len(path) < 1:
raise TypeError, "Cannot parse keyword query %r" % kwarg
tables2, joins2, where2, params2 = lookup_inner(path, clause, value, opts, opts.db_table, None)
tables.extend(tables2)
joins.update(joins2)
where.extend(where2)
params.extend(params2)
return tables, joins, where, params
class FieldFound(Exception):
"Exception used to short circuit field-finding operations."
pass
def find_field(name, field_list, use_accessor=False):
"""
Finds a field with a specific name in a list of field instances.
Returns None if there are no matches, or several matches.
"""
if use_accessor:
matches = [f for f in field_list if f.OLD_get_accessor_name() == name]
else:
matches = [f for f in field_list if f.name == name]
if len(matches) != 1:
return None
return matches[0]
def lookup_inner(path, clause, value, opts, table, column):
tables, joins, where, params = [], SortedDict(), [], []
current_opts = opts
current_table = table
current_column = column
intermediate_table = None
join_required = False
name = path.pop(0)
# Has the primary key been requested? If so, expand it out
# to be the name of the current class' primary key
if name is None:
name = current_opts.pk.name
# Try to find the name in the fields associated with the current class
try:
# Does the name belong to a defined many-to-many field?
field = find_field(name, current_opts.many_to_many)
if field:
new_table = current_table + LOOKUP_SEPARATOR + name
new_opts = field.rel.to._meta
new_column = new_opts.pk.column
# Need to create an intermediate table join over the m2m table
# This process hijacks current_table/column to point to the
# intermediate table.
current_table = "m2m_" + new_table
join_column = new_opts.object_name.lower() + '_id'
intermediate_table = field.get_m2m_db_table(current_opts)
raise FieldFound
# Does the name belong to a reverse defined many-to-many field?
field = find_field(name, current_opts.get_all_related_many_to_many_objects())
if field:
new_table = current_table + LOOKUP_SEPARATOR + name
new_opts = field.opts
new_column = new_opts.pk.column
# Need to create an intermediate table join over the m2m table.
# This process hijacks current_table/column to point to the
# intermediate table.
current_table = "m2m_" + new_table
join_column = new_opts.object_name.lower() + '_id'
intermediate_table = field.field.get_m2m_db_table(new_opts)
raise FieldFound
# Does the name belong to a one-to-many field?
field = find_field(name, current_opts.get_all_related_objects(), True)
if field:
new_table = table + LOOKUP_SEPARATOR + name
new_opts = field.opts
new_column = field.field.column
join_column = opts.pk.column
# 1-N fields MUST be joined, regardless of any other conditions.
join_required = True
raise FieldFound
# Does the name belong to a one-to-one, many-to-one, or regular field?
field = find_field(name, current_opts.fields)
if field:
if field.rel: # One-to-One/Many-to-one field
new_table = current_table + LOOKUP_SEPARATOR + name
new_opts = field.rel.to._meta
new_column = new_opts.pk.column
join_column = field.column
raise FieldFound
except FieldFound: # Match found, loop has been shortcut.
pass
except: # Any other exception; rethrow
raise
else: # No match found.
raise TypeError, "Cannot resolve keyword '%s' into field" % name
# Check to see if an intermediate join is required between current_table
# and new_table.
if intermediate_table:
joins[backend.quote_name(current_table)] = (
backend.quote_name(intermediate_table),
"INNER JOIN",
"%s.%s = %s.%s" % \
(backend.quote_name(table),
backend.quote_name(current_opts.pk.column),
backend.quote_name(current_table),
backend.quote_name(current_opts.object_name.lower() + '_id'))
)
if path:
if len(path) == 1 and path[0] in (new_opts.pk.name, None) \
and clause in ('exact', 'isnull') and not join_required:
# If the last name query is for a key, and the search is for
# isnull/exact, then the current (for N-1) or intermediate
# (for N-N) table can be used for the search - no need to join an
# extra table just to check the primary key.
new_table = current_table
else:
# There are 1 or more name queries pending, and we have ruled out
# any shortcuts; therefore, a join is required.
joins[backend.quote_name(new_table)] = (
backend.quote_name(new_opts.db_table),
"INNER JOIN",
"%s.%s = %s.%s" %
(backend.quote_name(current_table),
backend.quote_name(join_column),
backend.quote_name(new_table),
backend.quote_name(new_column))
)
# If we have made the join, we don't need to tell subsequent
# recursive calls about the column name we joined on.
join_column = None
# There are name queries remaining. Recurse deeper.
tables2, joins2, where2, params2 = lookup_inner(path, clause, value, new_opts, new_table, join_column)
tables.extend(tables2)
joins.update(joins2)
where.extend(where2)
params.extend(params2)
else:
# Evaluate clause on current table.
if name in (current_opts.pk.name, None) and clause in ('exact', 'isnull') and current_column:
# If this is an exact/isnull key search, and the last pass
# found/introduced a current/intermediate table that we can use to
# optimize the query, then use that column name.
column = current_column
else:
column = field.column
where.append(get_where_clause(clause, current_table + '.', column, value))
params.extend(field.get_db_prep_lookup(clause, value))
return tables, joins, where, params
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