django1/django/db/models/sql/query.py

1861 lines
77 KiB
Python

"""
Create SQL statements for QuerySets.
The code in here encapsulates all of the SQL construction so that QuerySets
themselves do not have to (and could be backed by things other than SQL
databases). The abstraction barrier only works one way: this module has to know
all about the internals of models in order to get the information it needs.
"""
from django.utils.copycompat import deepcopy
from django.utils.tree import Node
from django.utils.datastructures import SortedDict
from django.utils.encoding import force_unicode
from django.db import connections, DEFAULT_DB_ALIAS
from django.db.models import signals
from django.db.models.fields import FieldDoesNotExist
from django.db.models.query_utils import select_related_descend, InvalidQuery
from django.db.models.sql import aggregates as base_aggregates_module
from django.db.models.sql.constants import *
from django.db.models.sql.datastructures import EmptyResultSet, Empty, MultiJoin
from django.db.models.sql.expressions import SQLEvaluator
from django.db.models.sql.where import (WhereNode, Constraint, EverythingNode,
ExtraWhere, AND, OR)
from django.core.exceptions import FieldError
__all__ = ['Query', 'RawQuery']
class RawQuery(object):
"""
A single raw SQL query
"""
def __init__(self, sql, using, params=None):
self.validate_sql(sql)
self.params = params or ()
self.sql = sql
self.using = using
self.cursor = None
# Mirror some properties of a normal query so that
# the compiler can be used to process results.
self.low_mark, self.high_mark = 0, None # Used for offset/limit
self.extra_select = {}
self.aggregate_select = {}
def clone(self, using):
return RawQuery(self.sql, using, params=self.params)
def convert_values(self, value, field, connection):
"""Convert the database-returned value into a type that is consistent
across database backends.
By default, this defers to the underlying backend operations, but
it can be overridden by Query classes for specific backends.
"""
return connection.ops.convert_values(value, field)
def get_columns(self):
if self.cursor is None:
self._execute_query()
converter = connections[self.using].introspection.table_name_converter
return [converter(column_meta[0])
for column_meta in self.cursor.description]
def validate_sql(self, sql):
if not sql.lower().strip().startswith('select'):
raise InvalidQuery('Raw queries are limited to SELECT queries. Use '
'connection.cursor directly for other types of queries.')
def __iter__(self):
# Always execute a new query for a new iterator.
# This could be optimized with a cache at the expense of RAM.
self._execute_query()
if not connections[self.using].features.can_use_chunked_reads:
# If the database can't use chunked reads we need to make sure we
# evaluate the entire query up front.
result = list(self.cursor)
else:
result = self.cursor
return iter(result)
def __repr__(self):
return "<RawQuery: %r>" % (self.sql % self.params)
def _execute_query(self):
self.cursor = connections[self.using].cursor()
self.cursor.execute(self.sql, self.params)
class Query(object):
"""
A single SQL query.
"""
# SQL join types. These are part of the class because their string forms
# vary from database to database and can be customised by a subclass.
INNER = 'INNER JOIN'
LOUTER = 'LEFT OUTER JOIN'
alias_prefix = 'T'
query_terms = QUERY_TERMS
aggregates_module = base_aggregates_module
compiler = 'SQLCompiler'
def __init__(self, model, where=WhereNode):
self.model = model
self.alias_refcount = {}
self.alias_map = {} # Maps alias to join information
self.table_map = {} # Maps table names to list of aliases.
self.join_map = {}
self.rev_join_map = {} # Reverse of join_map.
self.quote_cache = {}
self.default_cols = True
self.default_ordering = True
self.standard_ordering = True
self.ordering_aliases = []
self.select_fields = []
self.related_select_fields = []
self.dupe_avoidance = {}
self.used_aliases = set()
self.filter_is_sticky = False
self.included_inherited_models = {}
# SQL-related attributes
self.select = []
self.tables = [] # Aliases in the order they are created.
self.where = where()
self.where_class = where
self.group_by = None
self.having = where()
self.order_by = []
self.low_mark, self.high_mark = 0, None # Used for offset/limit
self.distinct = False
self.select_related = False
self.related_select_cols = []
# SQL aggregate-related attributes
self.aggregates = SortedDict() # Maps alias -> SQL aggregate function
self.aggregate_select_mask = None
self._aggregate_select_cache = None
# Arbitrary maximum limit for select_related. Prevents infinite
# recursion. Can be changed by the depth parameter to select_related().
self.max_depth = 5
# These are for extensions. The contents are more or less appended
# verbatim to the appropriate clause.
self.extra = SortedDict() # Maps col_alias -> (col_sql, params).
self.extra_select_mask = None
self._extra_select_cache = None
self.extra_tables = ()
self.extra_order_by = ()
# A tuple that is a set of model field names and either True, if these
# are the fields to defer, or False if these are the only fields to
# load.
self.deferred_loading = (set(), True)
def __str__(self):
"""
Returns the query as a string of SQL with the parameter values
substituted in.
Parameter values won't necessarily be quoted correctly, since that is
done by the database interface at execution time.
"""
sql, params = self.get_compiler(DEFAULT_DB_ALIAS).as_sql()
return sql % params
def __deepcopy__(self, memo):
result = self.clone(memo=memo)
memo[id(self)] = result
return result
def __getstate__(self):
"""
Pickling support.
"""
obj_dict = self.__dict__.copy()
obj_dict['related_select_fields'] = []
obj_dict['related_select_cols'] = []
# Fields can't be pickled, so if a field list has been
# specified, we pickle the list of field names instead.
# None is also a possible value; that can pass as-is
obj_dict['select_fields'] = [
f is not None and f.name or None
for f in obj_dict['select_fields']
]
return obj_dict
def __setstate__(self, obj_dict):
"""
Unpickling support.
"""
# Rebuild list of field instances
opts = obj_dict['model']._meta
obj_dict['select_fields'] = [
name is not None and opts.get_field(name) or None
for name in obj_dict['select_fields']
]
self.__dict__.update(obj_dict)
def prepare(self):
return self
def get_compiler(self, using=None, connection=None):
if using is None and connection is None:
raise ValueError("Need either using or connection")
if using:
connection = connections[using]
# Check that the compiler will be able to execute the query
for alias, aggregate in self.aggregate_select.items():
connection.ops.check_aggregate_support(aggregate)
return connection.ops.compiler(self.compiler)(self, connection, using)
def get_meta(self):
"""
Returns the Options instance (the model._meta) from which to start
processing. Normally, this is self.model._meta, but it can be changed
by subclasses.
"""
return self.model._meta
def clone(self, klass=None, memo=None, **kwargs):
"""
Creates a copy of the current instance. The 'kwargs' parameter can be
used by clients to update attributes after copying has taken place.
"""
obj = Empty()
obj.__class__ = klass or self.__class__
obj.model = self.model
obj.alias_refcount = self.alias_refcount.copy()
obj.alias_map = self.alias_map.copy()
obj.table_map = self.table_map.copy()
obj.join_map = self.join_map.copy()
obj.rev_join_map = self.rev_join_map.copy()
obj.quote_cache = {}
obj.default_cols = self.default_cols
obj.default_ordering = self.default_ordering
obj.standard_ordering = self.standard_ordering
obj.included_inherited_models = self.included_inherited_models.copy()
obj.ordering_aliases = []
obj.select_fields = self.select_fields[:]
obj.related_select_fields = self.related_select_fields[:]
obj.dupe_avoidance = self.dupe_avoidance.copy()
obj.select = self.select[:]
obj.tables = self.tables[:]
obj.where = deepcopy(self.where, memo=memo)
obj.where_class = self.where_class
if self.group_by is None:
obj.group_by = None
else:
obj.group_by = self.group_by[:]
obj.having = deepcopy(self.having, memo=memo)
obj.order_by = self.order_by[:]
obj.low_mark, obj.high_mark = self.low_mark, self.high_mark
obj.distinct = self.distinct
obj.select_related = self.select_related
obj.related_select_cols = []
obj.aggregates = deepcopy(self.aggregates, memo=memo)
if self.aggregate_select_mask is None:
obj.aggregate_select_mask = None
else:
obj.aggregate_select_mask = self.aggregate_select_mask.copy()
# _aggregate_select_cache cannot be copied, as doing so breaks the
# (necessary) state in which both aggregates and
# _aggregate_select_cache point to the same underlying objects.
# It will get re-populated in the cloned queryset the next time it's
# used.
obj._aggregate_select_cache = None
obj.max_depth = self.max_depth
obj.extra = self.extra.copy()
if self.extra_select_mask is None:
obj.extra_select_mask = None
else:
obj.extra_select_mask = self.extra_select_mask.copy()
if self._extra_select_cache is None:
obj._extra_select_cache = None
else:
obj._extra_select_cache = self._extra_select_cache.copy()
obj.extra_tables = self.extra_tables
obj.extra_order_by = self.extra_order_by
obj.deferred_loading = deepcopy(self.deferred_loading, memo=memo)
if self.filter_is_sticky and self.used_aliases:
obj.used_aliases = self.used_aliases.copy()
else:
obj.used_aliases = set()
obj.filter_is_sticky = False
obj.__dict__.update(kwargs)
if hasattr(obj, '_setup_query'):
obj._setup_query()
return obj
def convert_values(self, value, field, connection):
"""Convert the database-returned value into a type that is consistent
across database backends.
By default, this defers to the underlying backend operations, but
it can be overridden by Query classes for specific backends.
"""
return connection.ops.convert_values(value, field)
def resolve_aggregate(self, value, aggregate, connection):
"""Resolve the value of aggregates returned by the database to
consistent (and reasonable) types.
This is required because of the predisposition of certain backends
to return Decimal and long types when they are not needed.
"""
if value is None:
if aggregate.is_ordinal:
return 0
# Return None as-is
return value
elif aggregate.is_ordinal:
# Any ordinal aggregate (e.g., count) returns an int
return int(value)
elif aggregate.is_computed:
# Any computed aggregate (e.g., avg) returns a float
return float(value)
else:
# Return value depends on the type of the field being processed.
return self.convert_values(value, aggregate.field, connection)
def get_aggregation(self, using):
"""
Returns the dictionary with the values of the existing aggregations.
"""
if not self.aggregate_select:
return {}
# If there is a group by clause, aggregating does not add useful
# information but retrieves only the first row. Aggregate
# over the subquery instead.
if self.group_by is not None:
from django.db.models.sql.subqueries import AggregateQuery
query = AggregateQuery(self.model)
obj = self.clone()
# Remove any aggregates marked for reduction from the subquery
# and move them to the outer AggregateQuery.
for alias, aggregate in self.aggregate_select.items():
if aggregate.is_summary:
query.aggregate_select[alias] = aggregate
del obj.aggregate_select[alias]
try:
query.add_subquery(obj, using)
except EmptyResultSet:
return dict(
(alias, None)
for alias in query.aggregate_select
)
else:
query = self
self.select = []
self.default_cols = False
self.extra = {}
self.remove_inherited_models()
query.clear_ordering(True)
query.clear_limits()
query.select_related = False
query.related_select_cols = []
query.related_select_fields = []
result = query.get_compiler(using).execute_sql(SINGLE)
if result is None:
result = [None for q in query.aggregate_select.items()]
return dict([
(alias, self.resolve_aggregate(val, aggregate, connection=connections[using]))
for (alias, aggregate), val
in zip(query.aggregate_select.items(), result)
])
def get_count(self, using):
"""
Performs a COUNT() query using the current filter constraints.
"""
obj = self.clone()
if len(self.select) > 1 or self.aggregate_select:
# If a select clause exists, then the query has already started to
# specify the columns that are to be returned.
# In this case, we need to use a subquery to evaluate the count.
from django.db.models.sql.subqueries import AggregateQuery
subquery = obj
subquery.clear_ordering(True)
subquery.clear_limits()
obj = AggregateQuery(obj.model)
try:
obj.add_subquery(subquery, using=using)
except EmptyResultSet:
# add_subquery evaluates the query, if it's an EmptyResultSet
# then there are can be no results, and therefore there the
# count is obviously 0
return 0
obj.add_count_column()
number = obj.get_aggregation(using=using)[None]
# Apply offset and limit constraints manually, since using LIMIT/OFFSET
# in SQL (in variants that provide them) doesn't change the COUNT
# output.
number = max(0, number - self.low_mark)
if self.high_mark is not None:
number = min(number, self.high_mark - self.low_mark)
return number
def has_results(self, using):
q = self.clone()
q.add_extra({'a': 1}, None, None, None, None, None)
q.select = []
q.select_fields = []
q.default_cols = False
q.select_related = False
q.set_extra_mask(('a',))
q.set_aggregate_mask(())
q.clear_ordering(True)
q.set_limits(high=1)
compiler = q.get_compiler(using=using)
return bool(compiler.execute_sql(SINGLE))
def combine(self, rhs, connector):
"""
Merge the 'rhs' query into the current one (with any 'rhs' effects
being applied *after* (that is, "to the right of") anything in the
current query. 'rhs' is not modified during a call to this function.
The 'connector' parameter describes how to connect filters from the
'rhs' query.
"""
assert self.model == rhs.model, \
"Cannot combine queries on two different base models."
assert self.can_filter(), \
"Cannot combine queries once a slice has been taken."
assert self.distinct == rhs.distinct, \
"Cannot combine a unique query with a non-unique query."
self.remove_inherited_models()
# Work out how to relabel the rhs aliases, if necessary.
change_map = {}
used = set()
conjunction = (connector == AND)
first = True
for alias in rhs.tables:
if not rhs.alias_refcount[alias]:
# An unused alias.
continue
promote = (rhs.alias_map[alias][JOIN_TYPE] == self.LOUTER)
new_alias = self.join(rhs.rev_join_map[alias],
(conjunction and not first), used, promote, not conjunction)
used.add(new_alias)
change_map[alias] = new_alias
first = False
# So that we don't exclude valid results in an "or" query combination,
# the first join that is exclusive to the lhs (self) must be converted
# to an outer join.
if not conjunction:
for alias in self.tables[1:]:
if self.alias_refcount[alias] == 1:
self.promote_alias(alias, True)
break
# Now relabel a copy of the rhs where-clause and add it to the current
# one.
if rhs.where:
w = deepcopy(rhs.where)
w.relabel_aliases(change_map)
if not self.where:
# Since 'self' matches everything, add an explicit "include
# everything" where-constraint so that connections between the
# where clauses won't exclude valid results.
self.where.add(EverythingNode(), AND)
elif self.where:
# rhs has an empty where clause.
w = self.where_class()
w.add(EverythingNode(), AND)
else:
w = self.where_class()
self.where.add(w, connector)
# Selection columns and extra extensions are those provided by 'rhs'.
self.select = []
for col in rhs.select:
if isinstance(col, (list, tuple)):
self.select.append((change_map.get(col[0], col[0]), col[1]))
else:
item = deepcopy(col)
item.relabel_aliases(change_map)
self.select.append(item)
self.select_fields = rhs.select_fields[:]
if connector == OR:
# It would be nice to be able to handle this, but the queries don't
# really make sense (or return consistent value sets). Not worth
# the extra complexity when you can write a real query instead.
if self.extra and rhs.extra:
raise ValueError("When merging querysets using 'or', you "
"cannot have extra(select=...) on both sides.")
self.extra.update(rhs.extra)
extra_select_mask = set()
if self.extra_select_mask is not None:
extra_select_mask.update(self.extra_select_mask)
if rhs.extra_select_mask is not None:
extra_select_mask.update(rhs.extra_select_mask)
if extra_select_mask:
self.set_extra_mask(extra_select_mask)
self.extra_tables += rhs.extra_tables
# Ordering uses the 'rhs' ordering, unless it has none, in which case
# the current ordering is used.
self.order_by = rhs.order_by and rhs.order_by[:] or self.order_by
self.extra_order_by = rhs.extra_order_by or self.extra_order_by
def deferred_to_data(self, target, callback):
"""
Converts the self.deferred_loading data structure to an alternate data
structure, describing the field that *will* be loaded. This is used to
compute the columns to select from the database and also by the
QuerySet class to work out which fields are being initialised on each
model. Models that have all their fields included aren't mentioned in
the result, only those that have field restrictions in place.
The "target" parameter is the instance that is populated (in place).
The "callback" is a function that is called whenever a (model, field)
pair need to be added to "target". It accepts three parameters:
"target", and the model and list of fields being added for that model.
"""
field_names, defer = self.deferred_loading
if not field_names:
return
columns = set()
orig_opts = self.model._meta
seen = {}
must_include = {self.model: set([orig_opts.pk])}
for field_name in field_names:
parts = field_name.split(LOOKUP_SEP)
cur_model = self.model
opts = orig_opts
for name in parts[:-1]:
old_model = cur_model
source = opts.get_field_by_name(name)[0]
cur_model = opts.get_field_by_name(name)[0].rel.to
opts = cur_model._meta
# Even if we're "just passing through" this model, we must add
# both the current model's pk and the related reference field
# to the things we select.
must_include[old_model].add(source)
add_to_dict(must_include, cur_model, opts.pk)
field, model, _, _ = opts.get_field_by_name(parts[-1])
if model is None:
model = cur_model
add_to_dict(seen, model, field)
if defer:
# We need to load all fields for each model, except those that
# appear in "seen" (for all models that appear in "seen"). The only
# slight complexity here is handling fields that exist on parent
# models.
workset = {}
for model, values in seen.iteritems():
for field, m in model._meta.get_fields_with_model():
if field in values:
continue
add_to_dict(workset, m or model, field)
for model, values in must_include.iteritems():
# If we haven't included a model in workset, we don't add the
# corresponding must_include fields for that model, since an
# empty set means "include all fields". That's why there's no
# "else" branch here.
if model in workset:
workset[model].update(values)
for model, values in workset.iteritems():
callback(target, model, values)
else:
for model, values in must_include.iteritems():
if model in seen:
seen[model].update(values)
else:
# As we've passed through this model, but not explicitly
# included any fields, we have to make sure it's mentioned
# so that only the "must include" fields are pulled in.
seen[model] = values
# Now ensure that every model in the inheritance chain is mentioned
# in the parent list. Again, it must be mentioned to ensure that
# only "must include" fields are pulled in.
for model in orig_opts.get_parent_list():
if model not in seen:
seen[model] = set()
for model, values in seen.iteritems():
callback(target, model, values)
def deferred_to_columns_cb(self, target, model, fields):
"""
Callback used by deferred_to_columns(). The "target" parameter should
be a set instance.
"""
table = model._meta.db_table
if table not in target:
target[table] = set()
for field in fields:
target[table].add(field.column)
def table_alias(self, table_name, create=False):
"""
Returns a table alias for the given table_name and whether this is a
new alias or not.
If 'create' is true, a new alias is always created. Otherwise, the
most recently created alias for the table (if one exists) is reused.
"""
current = self.table_map.get(table_name)
if not create and current:
alias = current[0]
self.alias_refcount[alias] += 1
return alias, False
# Create a new alias for this table.
if current:
alias = '%s%d' % (self.alias_prefix, len(self.alias_map) + 1)
current.append(alias)
else:
# The first occurence of a table uses the table name directly.
alias = table_name
self.table_map[alias] = [alias]
self.alias_refcount[alias] = 1
self.tables.append(alias)
return alias, True
def ref_alias(self, alias):
""" Increases the reference count for this alias. """
self.alias_refcount[alias] += 1
def unref_alias(self, alias):
""" Decreases the reference count for this alias. """
self.alias_refcount[alias] -= 1
def promote_alias(self, alias, unconditional=False):
"""
Promotes the join type of an alias to an outer join if it's possible
for the join to contain NULL values on the left. If 'unconditional' is
False, the join is only promoted if it is nullable, otherwise it is
always promoted.
Returns True if the join was promoted.
"""
if ((unconditional or self.alias_map[alias][NULLABLE]) and
self.alias_map[alias][JOIN_TYPE] != self.LOUTER):
data = list(self.alias_map[alias])
data[JOIN_TYPE] = self.LOUTER
self.alias_map[alias] = tuple(data)
return True
return False
def promote_alias_chain(self, chain, must_promote=False):
"""
Walks along a chain of aliases, promoting the first nullable join and
any joins following that. If 'must_promote' is True, all the aliases in
the chain are promoted.
"""
for alias in chain:
if self.promote_alias(alias, must_promote):
must_promote = True
def promote_unused_aliases(self, initial_refcounts, used_aliases):
"""
Given a "before" copy of the alias_refcounts dictionary (as
'initial_refcounts') and a collection of aliases that may have been
changed or created, works out which aliases have been created since
then and which ones haven't been used and promotes all of those
aliases, plus any children of theirs in the alias tree, to outer joins.
"""
# FIXME: There's some (a lot of!) overlap with the similar OR promotion
# in add_filter(). It's not quite identical, but is very similar. So
# pulling out the common bits is something for later.
considered = {}
for alias in self.tables:
if alias not in used_aliases:
continue
if (alias not in initial_refcounts or
self.alias_refcount[alias] == initial_refcounts[alias]):
parent = self.alias_map[alias][LHS_ALIAS]
must_promote = considered.get(parent, False)
promoted = self.promote_alias(alias, must_promote)
considered[alias] = must_promote or promoted
def change_aliases(self, change_map):
"""
Changes the aliases in change_map (which maps old-alias -> new-alias),
relabelling any references to them in select columns and the where
clause.
"""
assert set(change_map.keys()).intersection(set(change_map.values())) == set()
# 1. Update references in "select" (normal columns plus aliases),
# "group by", "where" and "having".
self.where.relabel_aliases(change_map)
self.having.relabel_aliases(change_map)
for columns in [self.select, self.group_by or []]:
for pos, col in enumerate(columns):
if isinstance(col, (list, tuple)):
old_alias = col[0]
columns[pos] = (change_map.get(old_alias, old_alias), col[1])
else:
col.relabel_aliases(change_map)
for mapping in [self.aggregates]:
for key, col in mapping.items():
if isinstance(col, (list, tuple)):
old_alias = col[0]
mapping[key] = (change_map.get(old_alias, old_alias), col[1])
else:
col.relabel_aliases(change_map)
# 2. Rename the alias in the internal table/alias datastructures.
for old_alias, new_alias in change_map.iteritems():
alias_data = list(self.alias_map[old_alias])
alias_data[RHS_ALIAS] = new_alias
t = self.rev_join_map[old_alias]
data = list(self.join_map[t])
data[data.index(old_alias)] = new_alias
self.join_map[t] = tuple(data)
self.rev_join_map[new_alias] = t
del self.rev_join_map[old_alias]
self.alias_refcount[new_alias] = self.alias_refcount[old_alias]
del self.alias_refcount[old_alias]
self.alias_map[new_alias] = tuple(alias_data)
del self.alias_map[old_alias]
table_aliases = self.table_map[alias_data[TABLE_NAME]]
for pos, alias in enumerate(table_aliases):
if alias == old_alias:
table_aliases[pos] = new_alias
break
for pos, alias in enumerate(self.tables):
if alias == old_alias:
self.tables[pos] = new_alias
break
for key, alias in self.included_inherited_models.items():
if alias in change_map:
self.included_inherited_models[key] = change_map[alias]
# 3. Update any joins that refer to the old alias.
for alias, data in self.alias_map.iteritems():
lhs = data[LHS_ALIAS]
if lhs in change_map:
data = list(data)
data[LHS_ALIAS] = change_map[lhs]
self.alias_map[alias] = tuple(data)
def bump_prefix(self, exceptions=()):
"""
Changes the alias prefix to the next letter in the alphabet and
relabels all the aliases. Even tables that previously had no alias will
get an alias after this call (it's mostly used for nested queries and
the outer query will already be using the non-aliased table name).
Subclasses who create their own prefix should override this method to
produce a similar result (a new prefix and relabelled aliases).
The 'exceptions' parameter is a container that holds alias names which
should not be changed.
"""
current = ord(self.alias_prefix)
assert current < ord('Z')
prefix = chr(current + 1)
self.alias_prefix = prefix
change_map = {}
for pos, alias in enumerate(self.tables):
if alias in exceptions:
continue
new_alias = '%s%d' % (prefix, pos)
change_map[alias] = new_alias
self.tables[pos] = new_alias
self.change_aliases(change_map)
def get_initial_alias(self):
"""
Returns the first alias for this query, after increasing its reference
count.
"""
if self.tables:
alias = self.tables[0]
self.ref_alias(alias)
else:
alias = self.join((None, self.model._meta.db_table, None, None))
return alias
def count_active_tables(self):
"""
Returns the number of tables in this query with a non-zero reference
count.
"""
return len([1 for count in self.alias_refcount.itervalues() if count])
def join(self, connection, always_create=False, exclusions=(),
promote=False, outer_if_first=False, nullable=False, reuse=None):
"""
Returns an alias for the join in 'connection', either reusing an
existing alias for that join or creating a new one. 'connection' is a
tuple (lhs, table, lhs_col, col) where 'lhs' is either an existing
table alias or a table name. The join correspods to the SQL equivalent
of::
lhs.lhs_col = table.col
If 'always_create' is True and 'reuse' is None, a new alias is always
created, regardless of whether one already exists or not. If
'always_create' is True and 'reuse' is a set, an alias in 'reuse' that
matches the connection will be returned, if possible. If
'always_create' is False, the first existing alias that matches the
'connection' is returned, if any. Otherwise a new join is created.
If 'exclusions' is specified, it is something satisfying the container
protocol ("foo in exclusions" must work) and specifies a list of
aliases that should not be returned, even if they satisfy the join.
If 'promote' is True, the join type for the alias will be LOUTER (if
the alias previously existed, the join type will be promoted from INNER
to LOUTER, if necessary).
If 'outer_if_first' is True and a new join is created, it will have the
LOUTER join type. This is used when joining certain types of querysets
and Q-objects together.
If 'nullable' is True, the join can potentially involve NULL values and
is a candidate for promotion (to "left outer") when combining querysets.
"""
lhs, table, lhs_col, col = connection
if lhs in self.alias_map:
lhs_table = self.alias_map[lhs][TABLE_NAME]
else:
lhs_table = lhs
if reuse and always_create and table in self.table_map:
# Convert the 'reuse' to case to be "exclude everything but the
# reusable set, minus exclusions, for this table".
exclusions = set(self.table_map[table]).difference(reuse).union(set(exclusions))
always_create = False
t_ident = (lhs_table, table, lhs_col, col)
if not always_create:
for alias in self.join_map.get(t_ident, ()):
if alias not in exclusions:
if lhs_table and not self.alias_refcount[self.alias_map[alias][LHS_ALIAS]]:
# The LHS of this join tuple is no longer part of the
# query, so skip this possibility.
continue
if self.alias_map[alias][LHS_ALIAS] != lhs:
continue
self.ref_alias(alias)
if promote:
self.promote_alias(alias)
return alias
# No reuse is possible, so we need a new alias.
alias, _ = self.table_alias(table, True)
if not lhs:
# Not all tables need to be joined to anything. No join type
# means the later columns are ignored.
join_type = None
elif promote or outer_if_first:
join_type = self.LOUTER
else:
join_type = self.INNER
join = (table, alias, join_type, lhs, lhs_col, col, nullable)
self.alias_map[alias] = join
if t_ident in self.join_map:
self.join_map[t_ident] += (alias,)
else:
self.join_map[t_ident] = (alias,)
self.rev_join_map[alias] = t_ident
return alias
def setup_inherited_models(self):
"""
If the model that is the basis for this QuerySet inherits other models,
we need to ensure that those other models have their tables included in
the query.
We do this as a separate step so that subclasses know which
tables are going to be active in the query, without needing to compute
all the select columns (this method is called from pre_sql_setup(),
whereas column determination is a later part, and side-effect, of
as_sql()).
"""
opts = self.model._meta
root_alias = self.tables[0]
seen = {None: root_alias}
# Skip all proxy to the root proxied model
proxied_model = get_proxied_model(opts)
for field, model in opts.get_fields_with_model():
if model not in seen:
if model is proxied_model:
seen[model] = root_alias
else:
link_field = opts.get_ancestor_link(model)
seen[model] = self.join((root_alias, model._meta.db_table,
link_field.column, model._meta.pk.column))
self.included_inherited_models = seen
def remove_inherited_models(self):
"""
Undoes the effects of setup_inherited_models(). Should be called
whenever select columns (self.select) are set explicitly.
"""
for key, alias in self.included_inherited_models.items():
if key:
self.unref_alias(alias)
self.included_inherited_models = {}
def add_aggregate(self, aggregate, model, alias, is_summary):
"""
Adds a single aggregate expression to the Query
"""
opts = model._meta
field_list = aggregate.lookup.split(LOOKUP_SEP)
if len(field_list) == 1 and aggregate.lookup in self.aggregates:
# Aggregate is over an annotation
field_name = field_list[0]
col = field_name
source = self.aggregates[field_name]
if not is_summary:
raise FieldError("Cannot compute %s('%s'): '%s' is an aggregate" % (
aggregate.name, field_name, field_name))
elif ((len(field_list) > 1) or
(field_list[0] not in [i.name for i in opts.fields]) or
self.group_by is None or
not is_summary):
# If:
# - the field descriptor has more than one part (foo__bar), or
# - the field descriptor is referencing an m2m/m2o field, or
# - this is a reference to a model field (possibly inherited), or
# - this is an annotation over a model field
# then we need to explore the joins that are required.
field, source, opts, join_list, last, _ = self.setup_joins(
field_list, opts, self.get_initial_alias(), False)
# Process the join chain to see if it can be trimmed
col, _, join_list = self.trim_joins(source, join_list, last, False)
# If the aggregate references a model or field that requires a join,
# those joins must be LEFT OUTER - empty join rows must be returned
# in order for zeros to be returned for those aggregates.
for column_alias in join_list:
self.promote_alias(column_alias, unconditional=True)
col = (join_list[-1], col)
else:
# The simplest cases. No joins required -
# just reference the provided column alias.
field_name = field_list[0]
source = opts.get_field(field_name)
col = field_name
# Add the aggregate to the query
aggregate.add_to_query(self, alias, col=col, source=source, is_summary=is_summary)
def add_filter(self, filter_expr, connector=AND, negate=False, trim=False,
can_reuse=None, process_extras=True):
"""
Add a single filter to the query. The 'filter_expr' is a pair:
(filter_string, value). E.g. ('name__contains', 'fred')
If 'negate' is True, this is an exclude() filter. It's important to
note that this method does not negate anything in the where-clause
object when inserting the filter constraints. This is because negated
filters often require multiple calls to add_filter() and the negation
should only happen once. So the caller is responsible for this (the
caller will normally be add_q(), so that as an example).
If 'trim' is True, we automatically trim the final join group (used
internally when constructing nested queries).
If 'can_reuse' is a set, we are processing a component of a
multi-component filter (e.g. filter(Q1, Q2)). In this case, 'can_reuse'
will be a set of table aliases that can be reused in this filter, even
if we would otherwise force the creation of new aliases for a join
(needed for nested Q-filters). The set is updated by this method.
If 'process_extras' is set, any extra filters returned from the table
joining process will be processed. This parameter is set to False
during the processing of extra filters to avoid infinite recursion.
"""
arg, value = filter_expr
parts = arg.split(LOOKUP_SEP)
if not parts:
raise FieldError("Cannot parse keyword query %r" % arg)
# Work out the lookup type and remove it from 'parts', if necessary.
if len(parts) == 1 or parts[-1] not in self.query_terms:
lookup_type = 'exact'
else:
lookup_type = parts.pop()
# By default, this is a WHERE clause. If an aggregate is referenced
# in the value, the filter will be promoted to a HAVING
having_clause = False
# Interpret '__exact=None' as the sql 'is NULL'; otherwise, reject all
# uses of None as a query value.
if value is None:
if lookup_type != 'exact':
raise ValueError("Cannot use None as a query value")
lookup_type = 'isnull'
value = True
elif callable(value):
value = value()
elif hasattr(value, 'evaluate'):
# If value is a query expression, evaluate it
value = SQLEvaluator(value, self)
having_clause = value.contains_aggregate
for alias, aggregate in self.aggregates.items():
if alias == parts[0]:
entry = self.where_class()
entry.add((aggregate, lookup_type, value), AND)
if negate:
entry.negate()
self.having.add(entry, AND)
return
opts = self.get_meta()
alias = self.get_initial_alias()
allow_many = trim or not negate
try:
field, target, opts, join_list, last, extra_filters = self.setup_joins(
parts, opts, alias, True, allow_many, can_reuse=can_reuse,
negate=negate, process_extras=process_extras)
except MultiJoin, e:
self.split_exclude(filter_expr, LOOKUP_SEP.join(parts[:e.level]),
can_reuse)
return
if (lookup_type == 'isnull' and value is True and not negate and
len(join_list) > 1):
# If the comparison is against NULL, we may need to use some left
# outer joins when creating the join chain. This is only done when
# needed, as it's less efficient at the database level.
self.promote_alias_chain(join_list)
# Process the join list to see if we can remove any inner joins from
# the far end (fewer tables in a query is better).
col, alias, join_list = self.trim_joins(target, join_list, last, trim)
if connector == OR:
# Some joins may need to be promoted when adding a new filter to a
# disjunction. We walk the list of new joins and where it diverges
# from any previous joins (ref count is 1 in the table list), we
# make the new additions (and any existing ones not used in the new
# join list) an outer join.
join_it = iter(join_list)
table_it = iter(self.tables)
join_it.next(), table_it.next()
table_promote = False
join_promote = False
for join in join_it:
table = table_it.next()
if join == table and self.alias_refcount[join] > 1:
continue
join_promote = self.promote_alias(join)
if table != join:
table_promote = self.promote_alias(table)
break
self.promote_alias_chain(join_it, join_promote)
self.promote_alias_chain(table_it, table_promote)
if having_clause:
if (alias, col) not in self.group_by:
self.group_by.append((alias, col))
self.having.add((Constraint(alias, col, field), lookup_type, value),
connector)
else:
self.where.add((Constraint(alias, col, field), lookup_type, value),
connector)
if negate:
self.promote_alias_chain(join_list)
if lookup_type != 'isnull':
if len(join_list) > 1:
for alias in join_list:
if self.alias_map[alias][JOIN_TYPE] == self.LOUTER:
j_col = self.alias_map[alias][RHS_JOIN_COL]
entry = self.where_class()
entry.add(
(Constraint(alias, j_col, None), 'isnull', True),
AND
)
entry.negate()
self.where.add(entry, AND)
break
if not (lookup_type == 'in'
and not hasattr(value, 'as_sql')
and not hasattr(value, '_as_sql')
and not value) and field.null:
# Leaky abstraction artifact: We have to specifically
# exclude the "foo__in=[]" case from this handling, because
# it's short-circuited in the Where class.
# We also need to handle the case where a subquery is provided
self.where.add((Constraint(alias, col, None), 'isnull', False), AND)
if can_reuse is not None:
can_reuse.update(join_list)
if process_extras:
for filter in extra_filters:
self.add_filter(filter, negate=negate, can_reuse=can_reuse,
process_extras=False)
def add_q(self, q_object, used_aliases=None):
"""
Adds a Q-object to the current filter.
Can also be used to add anything that has an 'add_to_query()' method.
"""
if used_aliases is None:
used_aliases = self.used_aliases
if hasattr(q_object, 'add_to_query'):
# Complex custom objects are responsible for adding themselves.
q_object.add_to_query(self, used_aliases)
else:
if self.where and q_object.connector != AND and len(q_object) > 1:
self.where.start_subtree(AND)
subtree = True
else:
subtree = False
connector = AND
for child in q_object.children:
if connector == OR:
refcounts_before = self.alias_refcount.copy()
self.where.start_subtree(connector)
if isinstance(child, Node):
self.add_q(child, used_aliases)
else:
self.add_filter(child, connector, q_object.negated,
can_reuse=used_aliases)
self.where.end_subtree()
if connector == OR:
# Aliases that were newly added or not used at all need to
# be promoted to outer joins if they are nullable relations.
# (they shouldn't turn the whole conditional into the empty
# set just because they don't match anything).
self.promote_unused_aliases(refcounts_before, used_aliases)
connector = q_object.connector
if q_object.negated:
self.where.negate()
if subtree:
self.where.end_subtree()
if self.filter_is_sticky:
self.used_aliases = used_aliases
def setup_joins(self, names, opts, alias, dupe_multis, allow_many=True,
allow_explicit_fk=False, can_reuse=None, negate=False,
process_extras=True):
"""
Compute the necessary table joins for the passage through the fields
given in 'names'. 'opts' is the Options class for the current model
(which gives the table we are joining to), 'alias' is the alias for the
table we are joining to. If dupe_multis is True, any many-to-many or
many-to-one joins will always create a new alias (necessary for
disjunctive filters). If can_reuse is not None, it's a list of aliases
that can be reused in these joins (nothing else can be reused in this
case). Finally, 'negate' is used in the same sense as for add_filter()
-- it indicates an exclude() filter, or something similar. It is only
passed in here so that it can be passed to a field's extra_filter() for
customised behaviour.
Returns the final field involved in the join, the target database
column (used for any 'where' constraint), the final 'opts' value and the
list of tables joined.
"""
joins = [alias]
last = [0]
dupe_set = set()
exclusions = set()
extra_filters = []
for pos, name in enumerate(names):
try:
exclusions.add(int_alias)
except NameError:
pass
exclusions.add(alias)
last.append(len(joins))
if name == 'pk':
name = opts.pk.name
try:
field, model, direct, m2m = opts.get_field_by_name(name)
except FieldDoesNotExist:
for f in opts.fields:
if allow_explicit_fk and name == f.attname:
# XXX: A hack to allow foo_id to work in values() for
# backwards compatibility purposes. If we dropped that
# feature, this could be removed.
field, model, direct, m2m = opts.get_field_by_name(f.name)
break
else:
names = opts.get_all_field_names() + self.aggregate_select.keys()
raise FieldError("Cannot resolve keyword %r into field. "
"Choices are: %s" % (name, ", ".join(names)))
if not allow_many and (m2m or not direct):
for alias in joins:
self.unref_alias(alias)
raise MultiJoin(pos + 1)
if model:
# The field lives on a base class of the current model.
# Skip the chain of proxy to the concrete proxied model
proxied_model = get_proxied_model(opts)
for int_model in opts.get_base_chain(model):
if int_model is proxied_model:
opts = int_model._meta
else:
lhs_col = opts.parents[int_model].column
dedupe = lhs_col in opts.duplicate_targets
if dedupe:
exclusions.update(self.dupe_avoidance.get(
(id(opts), lhs_col), ()))
dupe_set.add((opts, lhs_col))
opts = int_model._meta
alias = self.join((alias, opts.db_table, lhs_col,
opts.pk.column), exclusions=exclusions)
joins.append(alias)
exclusions.add(alias)
for (dupe_opts, dupe_col) in dupe_set:
self.update_dupe_avoidance(dupe_opts, dupe_col,
alias)
cached_data = opts._join_cache.get(name)
orig_opts = opts
dupe_col = direct and field.column or field.field.column
dedupe = dupe_col in opts.duplicate_targets
if dupe_set or dedupe:
if dedupe:
dupe_set.add((opts, dupe_col))
exclusions.update(self.dupe_avoidance.get((id(opts), dupe_col),
()))
if process_extras and hasattr(field, 'extra_filters'):
extra_filters.extend(field.extra_filters(names, pos, negate))
if direct:
if m2m:
# Many-to-many field defined on the current model.
if cached_data:
(table1, from_col1, to_col1, table2, from_col2,
to_col2, opts, target) = cached_data
else:
table1 = field.m2m_db_table()
from_col1 = opts.pk.column
to_col1 = field.m2m_column_name()
opts = field.rel.to._meta
table2 = opts.db_table
from_col2 = field.m2m_reverse_name()
to_col2 = opts.pk.column
target = opts.pk
orig_opts._join_cache[name] = (table1, from_col1,
to_col1, table2, from_col2, to_col2, opts,
target)
int_alias = self.join((alias, table1, from_col1, to_col1),
dupe_multis, exclusions, nullable=True,
reuse=can_reuse)
if int_alias == table2 and from_col2 == to_col2:
joins.append(int_alias)
alias = int_alias
else:
alias = self.join(
(int_alias, table2, from_col2, to_col2),
dupe_multis, exclusions, nullable=True,
reuse=can_reuse)
joins.extend([int_alias, alias])
elif field.rel:
# One-to-one or many-to-one field
if cached_data:
(table, from_col, to_col, opts, target) = cached_data
else:
opts = field.rel.to._meta
target = field.rel.get_related_field()
table = opts.db_table
from_col = field.column
to_col = target.column
orig_opts._join_cache[name] = (table, from_col, to_col,
opts, target)
alias = self.join((alias, table, from_col, to_col),
exclusions=exclusions, nullable=field.null)
joins.append(alias)
else:
# Non-relation fields.
target = field
break
else:
orig_field = field
field = field.field
if m2m:
# Many-to-many field defined on the target model.
if cached_data:
(table1, from_col1, to_col1, table2, from_col2,
to_col2, opts, target) = cached_data
else:
table1 = field.m2m_db_table()
from_col1 = opts.pk.column
to_col1 = field.m2m_reverse_name()
opts = orig_field.opts
table2 = opts.db_table
from_col2 = field.m2m_column_name()
to_col2 = opts.pk.column
target = opts.pk
orig_opts._join_cache[name] = (table1, from_col1,
to_col1, table2, from_col2, to_col2, opts,
target)
int_alias = self.join((alias, table1, from_col1, to_col1),
dupe_multis, exclusions, nullable=True,
reuse=can_reuse)
alias = self.join((int_alias, table2, from_col2, to_col2),
dupe_multis, exclusions, nullable=True,
reuse=can_reuse)
joins.extend([int_alias, alias])
else:
# One-to-many field (ForeignKey defined on the target model)
if cached_data:
(table, from_col, to_col, opts, target) = cached_data
else:
local_field = opts.get_field_by_name(
field.rel.field_name)[0]
opts = orig_field.opts
table = opts.db_table
from_col = local_field.column
to_col = field.column
target = opts.pk
orig_opts._join_cache[name] = (table, from_col, to_col,
opts, target)
alias = self.join((alias, table, from_col, to_col),
dupe_multis, exclusions, nullable=True,
reuse=can_reuse)
joins.append(alias)
for (dupe_opts, dupe_col) in dupe_set:
try:
self.update_dupe_avoidance(dupe_opts, dupe_col, int_alias)
except NameError:
self.update_dupe_avoidance(dupe_opts, dupe_col, alias)
if pos != len(names) - 1:
if pos == len(names) - 2:
raise FieldError("Join on field %r not permitted. Did you misspell %r for the lookup type?" % (name, names[pos + 1]))
else:
raise FieldError("Join on field %r not permitted." % name)
return field, target, opts, joins, last, extra_filters
def trim_joins(self, target, join_list, last, trim):
"""
Sometimes joins at the end of a multi-table sequence can be trimmed. If
the final join is against the same column as we are comparing against,
and is an inner join, we can go back one step in a join chain and
compare against the LHS of the join instead (and then repeat the
optimization). The result, potentially, involves less table joins.
The 'target' parameter is the final field being joined to, 'join_list'
is the full list of join aliases.
The 'last' list contains offsets into 'join_list', corresponding to
each component of the filter. Many-to-many relations, for example, add
two tables to the join list and we want to deal with both tables the
same way, so 'last' has an entry for the first of the two tables and
then the table immediately after the second table, in that case.
The 'trim' parameter forces the final piece of the join list to be
trimmed before anything. See the documentation of add_filter() for
details about this.
Returns the final active column and table alias and the new active
join_list.
"""
final = len(join_list)
penultimate = last.pop()
if penultimate == final:
penultimate = last.pop()
if trim and len(join_list) > 1:
extra = join_list[penultimate:]
join_list = join_list[:penultimate]
final = penultimate
penultimate = last.pop()
col = self.alias_map[extra[0]][LHS_JOIN_COL]
for alias in extra:
self.unref_alias(alias)
else:
col = target.column
alias = join_list[-1]
while final > 1:
join = self.alias_map[alias]
if col != join[RHS_JOIN_COL] or join[JOIN_TYPE] != self.INNER:
break
self.unref_alias(alias)
alias = join[LHS_ALIAS]
col = join[LHS_JOIN_COL]
join_list = join_list[:-1]
final -= 1
if final == penultimate:
penultimate = last.pop()
return col, alias, join_list
def update_dupe_avoidance(self, opts, col, alias):
"""
For a column that is one of multiple pointing to the same table, update
the internal data structures to note that this alias shouldn't be used
for those other columns.
"""
ident = id(opts)
for name in opts.duplicate_targets[col]:
try:
self.dupe_avoidance[ident, name].add(alias)
except KeyError:
self.dupe_avoidance[ident, name] = set([alias])
def split_exclude(self, filter_expr, prefix, can_reuse):
"""
When doing an exclude against any kind of N-to-many relation, we need
to use a subquery. This method constructs the nested query, given the
original exclude filter (filter_expr) and the portion up to the first
N-to-many relation field.
"""
query = Query(self.model)
query.add_filter(filter_expr, can_reuse=can_reuse)
query.bump_prefix()
query.clear_ordering(True)
query.set_start(prefix)
self.add_filter(('%s__in' % prefix, query), negate=True, trim=True,
can_reuse=can_reuse)
# If there's more than one join in the inner query (before any initial
# bits were trimmed -- which means the last active table is more than
# two places into the alias list), we need to also handle the
# possibility that the earlier joins don't match anything by adding a
# comparison to NULL (e.g. in
# Tag.objects.exclude(parent__parent__name='t1'), a tag with no parent
# would otherwise be overlooked).
active_positions = [pos for (pos, count) in
enumerate(query.alias_refcount.itervalues()) if count]
if active_positions[-1] > 1:
self.add_filter(('%s__isnull' % prefix, False), negate=True,
trim=True, can_reuse=can_reuse)
def set_limits(self, low=None, high=None):
"""
Adjusts the limits on the rows retrieved. We use low/high to set these,
as it makes it more Pythonic to read and write. When the SQL query is
created, they are converted to the appropriate offset and limit values.
Any limits passed in here are applied relative to the existing
constraints. So low is added to the current low value and both will be
clamped to any existing high value.
"""
if high is not None:
if self.high_mark is not None:
self.high_mark = min(self.high_mark, self.low_mark + high)
else:
self.high_mark = self.low_mark + high
if low is not None:
if self.high_mark is not None:
self.low_mark = min(self.high_mark, self.low_mark + low)
else:
self.low_mark = self.low_mark + low
def clear_limits(self):
"""
Clears any existing limits.
"""
self.low_mark, self.high_mark = 0, None
def can_filter(self):
"""
Returns True if adding filters to this instance is still possible.
Typically, this means no limits or offsets have been put on the results.
"""
return not self.low_mark and self.high_mark is None
def clear_select_fields(self):
"""
Clears the list of fields to select (but not extra_select columns).
Some queryset types completely replace any existing list of select
columns.
"""
self.select = []
self.select_fields = []
def add_fields(self, field_names, allow_m2m=True):
"""
Adds the given (model) fields to the select set. The field names are
added in the order specified.
"""
alias = self.get_initial_alias()
opts = self.get_meta()
try:
for name in field_names:
field, target, u2, joins, u3, u4 = self.setup_joins(
name.split(LOOKUP_SEP), opts, alias, False, allow_m2m,
True)
final_alias = joins[-1]
col = target.column
if len(joins) > 1:
join = self.alias_map[final_alias]
if col == join[RHS_JOIN_COL]:
self.unref_alias(final_alias)
final_alias = join[LHS_ALIAS]
col = join[LHS_JOIN_COL]
joins = joins[:-1]
self.promote_alias_chain(joins[1:])
self.select.append((final_alias, col))
self.select_fields.append(field)
except MultiJoin:
raise FieldError("Invalid field name: '%s'" % name)
except FieldError:
names = opts.get_all_field_names() + self.extra.keys() + self.aggregate_select.keys()
names.sort()
raise FieldError("Cannot resolve keyword %r into field. "
"Choices are: %s" % (name, ", ".join(names)))
self.remove_inherited_models()
def add_ordering(self, *ordering):
"""
Adds items from the 'ordering' sequence to the query's "order by"
clause. These items are either field names (not column names) --
possibly with a direction prefix ('-' or '?') -- or ordinals,
corresponding to column positions in the 'select' list.
If 'ordering' is empty, all ordering is cleared from the query.
"""
errors = []
for item in ordering:
if not ORDER_PATTERN.match(item):
errors.append(item)
if errors:
raise FieldError('Invalid order_by arguments: %s' % errors)
if ordering:
self.order_by.extend(ordering)
else:
self.default_ordering = False
def clear_ordering(self, force_empty=False):
"""
Removes any ordering settings. If 'force_empty' is True, there will be
no ordering in the resulting query (not even the model's default).
"""
self.order_by = []
self.extra_order_by = ()
if force_empty:
self.default_ordering = False
def set_group_by(self):
"""
Expands the GROUP BY clause required by the query.
This will usually be the set of all non-aggregate fields in the
return data. If the database backend supports grouping by the
primary key, and the query would be equivalent, the optimization
will be made automatically.
"""
self.group_by = []
for sel in self.select:
self.group_by.append(sel)
def add_count_column(self):
"""
Converts the query to do count(...) or count(distinct(pk)) in order to
get its size.
"""
if not self.distinct:
if not self.select:
count = self.aggregates_module.Count('*', is_summary=True)
else:
assert len(self.select) == 1, \
"Cannot add count col with multiple cols in 'select': %r" % self.select
count = self.aggregates_module.Count(self.select[0])
else:
opts = self.model._meta
if not self.select:
count = self.aggregates_module.Count((self.join((None, opts.db_table, None, None)), opts.pk.column),
is_summary=True, distinct=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'."
count = self.aggregates_module.Count(self.select[0], distinct=True)
# Distinct handling is done in Count(), so don't do it at this
# level.
self.distinct = False
# Set only aggregate to be the count column.
# Clear out the select cache to reflect the new unmasked aggregates.
self.aggregates = {None: count}
self.set_aggregate_mask(None)
self.group_by = None
def add_select_related(self, fields):
"""
Sets up the select_related data structure so that we only select
certain related models (as opposed to all models, when
self.select_related=True).
"""
field_dict = {}
for field in fields:
d = field_dict
for part in field.split(LOOKUP_SEP):
d = d.setdefault(part, {})
self.select_related = field_dict
self.related_select_cols = []
self.related_select_fields = []
def add_extra(self, select, select_params, where, params, tables, order_by):
"""
Adds data to the various extra_* attributes for user-created additions
to the query.
"""
if select:
# We need to pair any placeholder markers in the 'select'
# dictionary with their parameters in 'select_params' so that
# subsequent updates to the select dictionary also adjust the
# parameters appropriately.
select_pairs = SortedDict()
if select_params:
param_iter = iter(select_params)
else:
param_iter = iter([])
for name, entry in select.items():
entry = force_unicode(entry)
entry_params = []
pos = entry.find("%s")
while pos != -1:
entry_params.append(param_iter.next())
pos = entry.find("%s", pos + 2)
select_pairs[name] = (entry, entry_params)
# This is order preserving, since self.extra_select is a SortedDict.
self.extra.update(select_pairs)
if where or params:
self.where.add(ExtraWhere(where, params), AND)
if tables:
self.extra_tables += tuple(tables)
if order_by:
self.extra_order_by = order_by
def clear_deferred_loading(self):
"""
Remove any fields from the deferred loading set.
"""
self.deferred_loading = (set(), True)
def add_deferred_loading(self, field_names):
"""
Add the given list of model field names to the set of fields to
exclude from loading from the database when automatic column selection
is done. The new field names are added to any existing field names that
are deferred (or removed from any existing field names that are marked
as the only ones for immediate loading).
"""
# Fields on related models are stored in the literal double-underscore
# format, so that we can use a set datastructure. We do the foo__bar
# splitting and handling when computing the SQL colum names (as part of
# get_columns()).
existing, defer = self.deferred_loading
if defer:
# Add to existing deferred names.
self.deferred_loading = existing.union(field_names), True
else:
# Remove names from the set of any existing "immediate load" names.
self.deferred_loading = existing.difference(field_names), False
def add_immediate_loading(self, field_names):
"""
Add the given list of model field names to the set of fields to
retrieve when the SQL is executed ("immediate loading" fields). The
field names replace any existing immediate loading field names. If
there are field names already specified for deferred loading, those
names are removed from the new field_names before storing the new names
for immediate loading. (That is, immediate loading overrides any
existing immediate values, but respects existing deferrals.)
"""
existing, defer = self.deferred_loading
if defer:
# Remove any existing deferred names from the current set before
# setting the new names.
self.deferred_loading = set(field_names).difference(existing), False
else:
# Replace any existing "immediate load" field names.
self.deferred_loading = set(field_names), False
def get_loaded_field_names(self):
"""
If any fields are marked to be deferred, returns a dictionary mapping
models to a set of names in those fields that will be loaded. If a
model is not in the returned dictionary, none of it's fields are
deferred.
If no fields are marked for deferral, returns an empty dictionary.
"""
collection = {}
self.deferred_to_data(collection, self.get_loaded_field_names_cb)
return collection
def get_loaded_field_names_cb(self, target, model, fields):
"""
Callback used by get_deferred_field_names().
"""
target[model] = set([f.name for f in fields])
def set_aggregate_mask(self, names):
"Set the mask of aggregates that will actually be returned by the SELECT"
if names is None:
self.aggregate_select_mask = None
else:
self.aggregate_select_mask = set(names)
self._aggregate_select_cache = None
def set_extra_mask(self, names):
"""
Set the mask of extra select items that will be returned by SELECT,
we don't actually remove them from the Query since they might be used
later
"""
if names is None:
self.extra_select_mask = None
else:
self.extra_select_mask = set(names)
self._extra_select_cache = None
def _aggregate_select(self):
"""The SortedDict of aggregate columns that are not masked, and should
be used in the SELECT clause.
This result is cached for optimization purposes.
"""
if self._aggregate_select_cache is not None:
return self._aggregate_select_cache
elif self.aggregate_select_mask is not None:
self._aggregate_select_cache = SortedDict([
(k,v) for k,v in self.aggregates.items()
if k in self.aggregate_select_mask
])
return self._aggregate_select_cache
else:
return self.aggregates
aggregate_select = property(_aggregate_select)
def _extra_select(self):
if self._extra_select_cache is not None:
return self._extra_select_cache
elif self.extra_select_mask is not None:
self._extra_select_cache = SortedDict([
(k,v) for k,v in self.extra.items()
if k in self.extra_select_mask
])
return self._extra_select_cache
else:
return self.extra
extra_select = property(_extra_select)
def set_start(self, start):
"""
Sets the table from which to start joining. The start position is
specified by the related attribute from the base model. This will
automatically set to the select column to be the column linked from the
previous table.
This method is primarily for internal use and the error checking isn't
as friendly as add_filter(). Mostly useful for querying directly
against the join table of many-to-many relation in a subquery.
"""
opts = self.model._meta
alias = self.get_initial_alias()
field, col, opts, joins, last, extra = self.setup_joins(
start.split(LOOKUP_SEP), opts, alias, False)
select_col = self.alias_map[joins[1]][LHS_JOIN_COL]
select_alias = alias
# The call to setup_joins added an extra reference to everything in
# joins. Reverse that.
for alias in joins:
self.unref_alias(alias)
# We might be able to trim some joins from the front of this query,
# providing that we only traverse "always equal" connections (i.e. rhs
# is *always* the same value as lhs).
for alias in joins[1:]:
join_info = self.alias_map[alias]
if (join_info[LHS_JOIN_COL] != select_col
or join_info[JOIN_TYPE] != self.INNER):
break
self.unref_alias(select_alias)
select_alias = join_info[RHS_ALIAS]
select_col = join_info[RHS_JOIN_COL]
self.select = [(select_alias, select_col)]
self.remove_inherited_models()
def get_order_dir(field, default='ASC'):
"""
Returns the field name and direction for an order specification. For
example, '-foo' is returned as ('foo', 'DESC').
The 'default' param is used to indicate which way no prefix (or a '+'
prefix) should sort. The '-' prefix always sorts the opposite way.
"""
dirn = ORDER_DIR[default]
if field[0] == '-':
return field[1:], dirn[1]
return field, dirn[0]
def setup_join_cache(sender, **kwargs):
"""
The information needed to join between model fields is something that is
invariant over the life of the model, so we cache it in the model's Options
class, rather than recomputing it all the time.
This method initialises the (empty) cache when the model is created.
"""
sender._meta._join_cache = {}
signals.class_prepared.connect(setup_join_cache)
def add_to_dict(data, key, value):
"""
A helper function to add "value" to the set of values for "key", whether or
not "key" already exists.
"""
if key in data:
data[key].add(value)
else:
data[key] = set([value])
def get_proxied_model(opts):
int_opts = opts
proxied_model = None
while int_opts.proxy:
proxied_model = int_opts.proxy_for_model
int_opts = proxied_model._meta
return proxied_model