blinkster: comparison web/lib/django/db/models/sql/query.py

equal deleted inserted replaced

--1:000000000000
+:0d40e90630ef
+"""
+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 copy import deepcopy
+from django.utils.tree import Node
+from django.utils.datastructures import SortedDict
+from django.utils.encoding import force_unicode
+from django.db.backends.util import truncate_name
+from django.db import connection
+from django.db.models import signals
+from django.db.models.fields import FieldDoesNotExist
+from django.db.models.query_utils import select_related_descend
+from django.db.models.sql import aggregates as base_aggregates_module
+from django.db.models.sql.expressions import SQLEvaluator
+from django.db.models.sql.where import WhereNode, Constraint, EverythingNode, AND, OR
+from django.core.exceptions import FieldError
+from datastructures import EmptyResultSet, Empty, MultiJoin
+from constants import *
+try:
+set
+except NameError:
+from sets import Set as set     # Python 2.3 fallback
+__all__ = ['Query', 'BaseQuery']
+class BaseQuery(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
+def __init__(self, model, connection, where=WhereNode):
+self.model = model
+self.connection = connection
+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_where = ()
+self.extra_params = ()
+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.as_sql()
+return sql % params
+def __deepcopy__(self, memo):
+result= self.clone()
+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'] = []
+del obj_dict['connection']
+# 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
+obj_dict['select_fields'] = [
+name is not None and obj_dict['model']._meta.get_field(name) or None
+for name in obj_dict['select_fields']
+]
+self.__dict__.update(obj_dict)
+# XXX: Need a better solution for this when multi-db stuff is
+# supported. It's the only class-reference to the module-level
+# connection variable.
+self.connection = connection
+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 quote_name_unless_alias(self, name):
+"""
+A wrapper around connection.ops.quote_name that doesn't quote aliases
+for table names. This avoids problems with some SQL dialects that treat
+quoted strings specially (e.g. PostgreSQL).
+"""
+if name in self.quote_cache:
+return self.quote_cache[name]
+if ((name in self.alias_map and name not in self.table_map) or
+name in self.extra_select):
+self.quote_cache[name] = name
+return name
+r = self.connection.ops.quote_name(name)
+self.quote_cache[name] = r
+return r
+def clone(self, klass=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.connection = self.connection
+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)
+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)
+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)
+if self.aggregate_select_mask is None:
+obj.aggregate_select_mask = None
+else:
+obj.aggregate_select_mask = self.aggregate_select_mask.copy()
+if self._aggregate_select_cache is None:
+obj._aggregate_select_cache = None
+else:
+obj._aggregate_select_cache = self._aggregate_select_cache.copy()
+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_where = self.extra_where
+obj.extra_params = self.extra_params
+obj.extra_order_by = self.extra_order_by
+obj.deferred_loading = deepcopy(self.deferred_loading)
+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):
+"""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 self.connection.ops.convert_values(value, field)
+def resolve_aggregate(self, value, aggregate):
+"""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)
+def results_iter(self):
+"""
+Returns an iterator over the results from executing this query.
+"""
+resolve_columns = hasattr(self, 'resolve_columns')
+fields = None
+for rows in self.execute_sql(MULTI):
+for row in rows:
+if resolve_columns:
+if fields is None:
+# We only set this up here because
+# related_select_fields isn't populated until
+# execute_sql() has been called.
+if self.select_fields:
+fields = self.select_fields + self.related_select_fields
+else:
+fields = self.model._meta.fields
+row = self.resolve_columns(row, fields)
+if self.aggregate_select:
+aggregate_start = len(self.extra_select.keys()) + len(self.select)
+aggregate_end = aggregate_start + len(self.aggregate_select)
+row = tuple(row[:aggregate_start]) + tuple([
+self.resolve_aggregate(value, aggregate)
+for (alias, aggregate), value
+in zip(self.aggregate_select.items(), row[aggregate_start:aggregate_end])
+]) + tuple(row[aggregate_end:])
+yield row
+def get_aggregation(self):
+"""
+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 subqueries import AggregateQuery
+query = AggregateQuery(self.model, self.connection)
+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]
+query.add_subquery(obj)
+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.execute_sql(SINGLE)
+if result is None:
+result = [None for q in query.aggregate_select.items()]
+return dict([
+(alias, self.resolve_aggregate(val, aggregate))
+for (alias, aggregate), val
+in zip(query.aggregate_select.items(), result)
+])
+def get_count(self):
+"""
+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 subqueries import AggregateQuery
+subquery = obj
+subquery.clear_ordering(True)
+subquery.clear_limits()
+obj = AggregateQuery(obj.model, obj.connection)
+obj.add_subquery(subquery)
+obj.add_count_column()
+number = obj.get_aggregation()[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 as_sql(self, with_limits=True, with_col_aliases=False):
+"""
+Creates the SQL for this query. Returns the SQL string and list of
+parameters.
+If 'with_limits' is False, any limit/offset information is not included
+in the query.
+"""
+self.pre_sql_setup()
+out_cols = self.get_columns(with_col_aliases)
+ordering, ordering_group_by = self.get_ordering()
+# This must come after 'select' and 'ordering' -- see docstring of
+# get_from_clause() for details.
+from_, f_params = self.get_from_clause()
+qn = self.quote_name_unless_alias
+where, w_params = self.where.as_sql(qn=qn)
+having, h_params = self.having.as_sql(qn=qn)
+params = []
+for val in self.extra_select.itervalues():
+params.extend(val[1])
+result = ['SELECT']
+if self.distinct:
+result.append('DISTINCT')
+result.append(', '.join(out_cols + self.ordering_aliases))
+result.append('FROM')
+result.extend(from_)
+params.extend(f_params)
+if where:
+result.append('WHERE %s' % where)
+params.extend(w_params)
+if self.extra_where:
+if not where:
+result.append('WHERE')
+else:
+result.append('AND')
+result.append(' AND '.join(self.extra_where))
+grouping, gb_params = self.get_grouping()
+if grouping:
+if ordering:
+# If the backend can't group by PK (i.e., any database
+# other than MySQL), then any fields mentioned in the
+# ordering clause needs to be in the group by clause.
+if not self.connection.features.allows_group_by_pk:
+for col, col_params in ordering_group_by:
+if col not in grouping:
+grouping.append(str(col))
+gb_params.extend(col_params)
+else:
+ordering = self.connection.ops.force_no_ordering()
+result.append('GROUP BY %s' % ', '.join(grouping))
+params.extend(gb_params)
+if having:
+result.append('HAVING %s' % having)
+params.extend(h_params)
+if ordering:
+result.append('ORDER BY %s' % ', '.join(ordering))
+if with_limits:
+if self.high_mark is not None:
+result.append('LIMIT %d' % (self.high_mark - self.low_mark))
+if self.low_mark:
+if self.high_mark is None:
+val = self.connection.ops.no_limit_value()
+if val:
+result.append('LIMIT %d' % val)
+result.append('OFFSET %d' % self.low_mark)
+params.extend(self.extra_params)
+return ' '.join(result), tuple(params)
+def as_nested_sql(self):
+"""
+Perform the same functionality as the as_sql() method, returning an
+SQL string and parameters. However, the alias prefixes are bumped
+beforehand (in a copy -- the current query isn't changed) and any
+ordering is removed.
+Used when nesting this query inside another.
+"""
+obj = self.clone()
+obj.clear_ordering(True)
+obj.bump_prefix()
+return obj.as_sql()
+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.")
+if self.extra_where and rhs.extra_where:
+raise ValueError("When merging querysets using 'or', you "
+"cannot have extra(where=...) 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
+self.extra_where += rhs.extra_where
+self.extra_params += rhs.extra_params
+# 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 pre_sql_setup(self):
+"""
+Does any necessary class setup immediately prior to producing SQL. This
+is for things that can't necessarily be done in __init__ because we
+might not have all the pieces in place at that time.
+"""
+if not self.tables:
+self.join((None, self.model._meta.db_table, None, None))
+if (not self.select and self.default_cols and not
+self.included_inherited_models):
+self.setup_inherited_models()
+if self.select_related and not self.related_select_cols:
+self.fill_related_selections()
+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 in model._meta.local_fields:
+if field in values:
+continue
+add_to_dict(workset, 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(self):
+"""
+Converts the self.deferred_loading data structure to mapping of table
+names to sets of column names which are to be loaded. Returns the
+dictionary.
+"""
+columns = {}
+self.deferred_to_data(columns, self.deferred_to_columns_cb)
+return columns
+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 get_columns(self, with_aliases=False):
+"""
+Returns the list of columns to use in the select statement. If no
+columns have been specified, returns all columns relating to fields in
+the model.
+If 'with_aliases' is true, any column names that are duplicated
+(without the table names) are given unique aliases. This is needed in
+some cases to avoid ambiguity with nested queries.
+"""
+qn = self.quote_name_unless_alias
+qn2 = self.connection.ops.quote_name
+result = ['(%s) AS %s' % (col[0], qn2(alias)) for alias, col in self.extra_select.iteritems()]
+aliases = set(self.extra_select.keys())
+if with_aliases:
+col_aliases = aliases.copy()
+else:
+col_aliases = set()
+if self.select:
+only_load = self.deferred_to_columns()
+for col in self.select:
+if isinstance(col, (list, tuple)):
+alias, column = col
+table = self.alias_map[alias][TABLE_NAME]
+if table in only_load and col not in only_load[table]:
+continue
+r = '%s.%s' % (qn(alias), qn(column))
+if with_aliases:
+if col[1] in col_aliases:
+c_alias = 'Col%d' % len(col_aliases)
+result.append('%s AS %s' % (r, c_alias))
+aliases.add(c_alias)
+col_aliases.add(c_alias)
+else:
+result.append('%s AS %s' % (r, qn2(col[1])))
+aliases.add(r)
+col_aliases.add(col[1])
+else:
+result.append(r)
+aliases.add(r)
+col_aliases.add(col[1])
+else:
+result.append(col.as_sql(quote_func=qn))
+if hasattr(col, 'alias'):
+aliases.add(col.alias)
+col_aliases.add(col.alias)
+elif self.default_cols:
+cols, new_aliases = self.get_default_columns(with_aliases,
+col_aliases)
+result.extend(cols)
+aliases.update(new_aliases)
+result.extend([
+'%s%s' % (
+aggregate.as_sql(quote_func=qn),
+alias is not None and ' AS %s' % qn(alias) or ''
+)
+for alias, aggregate in self.aggregate_select.items()
+])
+for table, col in self.related_select_cols:
+r = '%s.%s' % (qn(table), qn(col))
+if with_aliases and col in col_aliases:
+c_alias = 'Col%d' % len(col_aliases)
+result.append('%s AS %s' % (r, c_alias))
+aliases.add(c_alias)
+col_aliases.add(c_alias)
+else:
+result.append(r)
+aliases.add(r)
+col_aliases.add(col)
+self._select_aliases = aliases
+return result
+def get_default_columns(self, with_aliases=False, col_aliases=None,
+start_alias=None, opts=None, as_pairs=False):
+"""
+Computes the default columns for selecting every field in the base
+model. Will sometimes be called to pull in related models (e.g. via
+select_related), in which case "opts" and "start_alias" will be given
+to provide a starting point for the traversal.
+Returns a list of strings, quoted appropriately for use in SQL
+directly, as well as a set of aliases used in the select statement (if
+'as_pairs' is True, returns a list of (alias, col_name) pairs instead
+of strings as the first component and None as the second component).
+"""
+result = []
+if opts is None:
+opts = self.model._meta
+qn = self.quote_name_unless_alias
+qn2 = self.connection.ops.quote_name
+aliases = set()
+only_load = self.deferred_to_columns()
+# Skip all proxy to the root proxied model
+proxied_model = get_proxied_model(opts)
+if start_alias:
+seen = {None: start_alias}
+for field, model in opts.get_fields_with_model():
+if start_alias:
+try:
+alias = seen[model]
+except KeyError:
+if model is proxied_model:
+alias = start_alias
+else:
+link_field = opts.get_ancestor_link(model)
+alias = self.join((start_alias, model._meta.db_table,
+link_field.column, model._meta.pk.column))
+seen[model] = alias
+else:
+# If we're starting from the base model of the queryset, the
+# aliases will have already been set up in pre_sql_setup(), so
+# we can save time here.
+alias = self.included_inherited_models[model]
+table = self.alias_map[alias][TABLE_NAME]
+if table in only_load and field.column not in only_load[table]:
+continue
+if as_pairs:
+result.append((alias, field.column))
+aliases.add(alias)
+continue
+if with_aliases and field.column in col_aliases:
+c_alias = 'Col%d' % len(col_aliases)
+result.append('%s.%s AS %s' % (qn(alias),
+qn2(field.column), c_alias))
+col_aliases.add(c_alias)
+aliases.add(c_alias)
+else:
+r = '%s.%s' % (qn(alias), qn2(field.column))
+result.append(r)
+aliases.add(r)
+if with_aliases:
+col_aliases.add(field.column)
+return result, aliases
+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 a list any extra parameters that
+need to be included. Sub-classes, can override this to create a
+from-clause via a "select".
+This should only be called after any SQL construction methods that
+might change the tables we need. This means the select columns and
+ordering must be done first.
+"""
+result = []
+qn = self.quote_name_unless_alias
+qn2 = self.connection.ops.quote_name
+first = True
+for alias in self.tables:
+if not self.alias_refcount[alias]:
+continue
+try:
+name, alias, join_type, lhs, lhs_col, col, nullable = self.alias_map[alias]
+except KeyError:
+# Extra tables can end up in self.tables, but not in the
+# alias_map if they aren't in a join. That's OK. We skip them.
+continue
+alias_str = (alias != name and ' %s' % alias or '')
+if join_type and not first:
+result.append('%s %s%s ON (%s.%s = %s.%s)'
+% (join_type, qn(name), alias_str, qn(lhs),
+qn2(lhs_col), qn(alias), qn2(col)))
+else:
+connector = not first and ', ' or ''
+result.append('%s%s%s' % (connector, qn(name), alias_str))
+first = False
+for t in self.extra_tables:
+alias, unused = self.table_alias(t)
+# Only add the alias if it's not already present (the table_alias()
+# calls increments the refcount, so an alias refcount of one means
+# this is the only reference.
+if alias not in self.alias_map or self.alias_refcount[alias] == 1:
+connector = not first and ', ' or ''
+result.append('%s%s' % (connector, qn(alias)))
+first = False
+return result, []
+def get_grouping(self):
+"""
+Returns a tuple representing the SQL elements in the "group by" clause.
+"""
+qn = self.quote_name_unless_alias
+result, params = [], []
+if self.group_by is not None:
+group_by = self.group_by or []
+extra_selects = []
+for extra_select, extra_params in self.extra_select.itervalues():
+extra_selects.append(extra_select)
+params.extend(extra_params)
+for col in group_by + self.related_select_cols + extra_selects:
+if isinstance(col, (list, tuple)):
+result.append('%s.%s' % (qn(col[0]), qn(col[1])))
+elif hasattr(col, 'as_sql'):
+result.append(col.as_sql(qn))
+else:
+result.append(str(col))
+return result, params
+def get_ordering(self):
+"""
+Returns a tuple containing a list representing the SQL elements in the
+"order by" clause, and the list of SQL elements that need to be added
+to the GROUP BY clause as a result of the ordering.
+Also sets the ordering_aliases attribute on this instance to a list of
+extra aliases needed in the select.
+Determining the ordering SQL can change the tables we need to include,
+so this should be run *before* get_from_clause().
+"""
+if self.extra_order_by:
+ordering = self.extra_order_by
+elif not self.default_ordering:
+ordering = self.order_by
+else:
+ordering = self.order_by or self.model._meta.ordering
+qn = self.quote_name_unless_alias
+qn2 = self.connection.ops.quote_name
+distinct = self.distinct
+select_aliases = self._select_aliases
+result = []
+group_by = []
+ordering_aliases = []
+if self.standard_ordering:
+asc, desc = ORDER_DIR['ASC']
+else:
+asc, desc = ORDER_DIR['DESC']
+# It's possible, due to model inheritance, that normal usage might try
+# to include the same field more than once in the ordering. We track
+# the table/column pairs we use and discard any after the first use.
+processed_pairs = set()
+for field in ordering:
+if field == '?':
+result.append(self.connection.ops.random_function_sql())
+continue
+if isinstance(field, int):
+if field < 0:
+order = desc
+field = -field
+else:
+order = asc
+result.append('%s %s' % (field, order))
+group_by.append((field, []))
+continue
+col, order = get_order_dir(field, asc)
+if col in self.aggregate_select:
+result.append('%s %s' % (col, order))
+continue
+if '.' in field:
+# This came in through an extra(order_by=...) addition. Pass it
+# on verbatim.
+table, col = col.split('.', 1)
+if (table, col) not in processed_pairs:
+elt = '%s.%s' % (qn(table), col)
+processed_pairs.add((table, col))
+if not distinct or elt in select_aliases:
+result.append('%s %s' % (elt, order))
+group_by.append((elt, []))
+elif get_order_dir(field)[0] not in self.extra_select:
+# 'col' is of the form 'field' or 'field1__field2' or
+# '-field1__field2__field', etc.
+for table, col, order in self.find_ordering_name(field,
+self.model._meta, default_order=asc):
+if (table, col) not in processed_pairs:
+elt = '%s.%s' % (qn(table), qn2(col))
+processed_pairs.add((table, col))
+if distinct and elt not in select_aliases:
+ordering_aliases.append(elt)
+result.append('%s %s' % (elt, order))
+group_by.append((elt, []))
+else:
+elt = qn2(col)
+if distinct and col not in select_aliases:
+ordering_aliases.append(elt)
+result.append('%s %s' % (elt, order))
+group_by.append(self.extra_select[col])
+self.ordering_aliases = ordering_aliases
+return result, group_by
+def find_ordering_name(self, name, opts, alias=None, default_order='ASC',
+already_seen=None):
+"""
+Returns the table alias (the name might be ambiguous, the alias will
+not be) and column name for ordering by the given 'name' parameter.
+The 'name' is of the form 'field1__field2__...__fieldN'.
+"""
+name, order = get_order_dir(name, default_order)
+pieces = name.split(LOOKUP_SEP)
+if not alias:
+alias = self.get_initial_alias()
+field, target, opts, joins, last, extra = self.setup_joins(pieces,
+opts, alias, False)
+alias = joins[-1]
+col = target.column
+if not field.rel:
+# To avoid inadvertent trimming of a necessary alias, use the
+# refcount to show that we are referencing a non-relation field on
+# the model.
+self.ref_alias(alias)
+# Must use left outer joins for nullable fields and their relations.
+self.promote_alias_chain(joins,
+self.alias_map[joins[0]][JOIN_TYPE] == self.LOUTER)
+# If we get to this point and the field is a relation to another model,
+# append the default ordering for that model.
+if field.rel and len(joins) > 1 and opts.ordering:
+# Firstly, avoid infinite loops.
+if not already_seen:
+already_seen = set()
+join_tuple = tuple([self.alias_map[j][TABLE_NAME] for j in joins])
+if join_tuple in already_seen:
+raise FieldError('Infinite loop caused by ordering.')
+already_seen.add(join_tuple)
+results = []
+for item in opts.ordering:
+results.extend(self.find_ordering_name(item, opts, alias,
+order, already_seen))
+return results
+if alias:
+# We have to do the same "final join" optimisation as in
+# add_filter, since the final column might not otherwise be part of
+# the select set (so we can't order on it).
+while 1:
+join = self.alias_map[alias]
+if col != join[RHS_JOIN_COL]:
+break
+self.unref_alias(alias)
+alias = join[LHS_ALIAS]
+col = join[LHS_JOIN_COL]
+return [(alias, col, order)]
+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.aggregates.values(), 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)
+# 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 fill_related_selections(self, opts=None, root_alias=None, cur_depth=1,
+used=None, requested=None, restricted=None, nullable=None,
+dupe_set=None, avoid_set=None):
+"""
+Fill in the information needed for a select_related query. The current
+depth is measured as the number of connections away from the root model
+(for example, cur_depth=1 means we are looking at models with direct
+connections to the root model).
+"""
+if not restricted and self.max_depth and cur_depth > self.max_depth:
+# We've recursed far enough; bail out.
+return
+if not opts:
+opts = self.get_meta()
+root_alias = self.get_initial_alias()
+self.related_select_cols = []
+self.related_select_fields = []
+if not used:
+used = set()
+if dupe_set is None:
+dupe_set = set()
+if avoid_set is None:
+avoid_set = set()
+orig_dupe_set = dupe_set
+# Setup for the case when only particular related fields should be
+# included in the related selection.
+if requested is None and restricted is not False:
+if isinstance(self.select_related, dict):
+requested = self.select_related
+restricted = True
+else:
+restricted = False
+for f, model in opts.get_fields_with_model():
+if not select_related_descend(f, restricted, requested):
+continue
+# The "avoid" set is aliases we want to avoid just for this
+# particular branch of the recursion. They aren't permanently
+# forbidden from reuse in the related selection tables (which is
+# what "used" specifies).
+avoid = avoid_set.copy()
+dupe_set = orig_dupe_set.copy()
+table = f.rel.to._meta.db_table
+if nullable or f.null:
+promote = True
+else:
+promote = False
+if model:
+int_opts = opts
+alias = root_alias
+alias_chain = []
+for int_model in opts.get_base_chain(model):
+# Proxy model have elements in base chain
+# with no parents, assign the new options
+# object and skip to the next base in that
+# case
+if not int_opts.parents[int_model]:
+int_opts = int_model._meta
+continue
+lhs_col = int_opts.parents[int_model].column
+dedupe = lhs_col in opts.duplicate_targets
+if dedupe:
+avoid.update(self.dupe_avoidance.get(id(opts), lhs_col),
+())
+dupe_set.add((opts, lhs_col))
+int_opts = int_model._meta
+alias = self.join((alias, int_opts.db_table, lhs_col,
+int_opts.pk.column), exclusions=used,
+promote=promote)
+alias_chain.append(alias)
+for (dupe_opts, dupe_col) in dupe_set:
+self.update_dupe_avoidance(dupe_opts, dupe_col, alias)
+if self.alias_map[root_alias][JOIN_TYPE] == self.LOUTER:
+self.promote_alias_chain(alias_chain, True)
+else:
+alias = root_alias
+dedupe = f.column in opts.duplicate_targets
+if dupe_set or dedupe:
+avoid.update(self.dupe_avoidance.get((id(opts), f.column), ()))
+if dedupe:
+dupe_set.add((opts, f.column))
+alias = self.join((alias, table, f.column,
+f.rel.get_related_field().column),
+exclusions=used.union(avoid), promote=promote)
+used.add(alias)
+columns, aliases = self.get_default_columns(start_alias=alias,
+opts=f.rel.to._meta, as_pairs=True)
+self.related_select_cols.extend(columns)
+if self.alias_map[alias][JOIN_TYPE] == self.LOUTER:
+self.promote_alias_chain(aliases, True)
+self.related_select_fields.extend(f.rel.to._meta.fields)
+if restricted:
+next = requested.get(f.name, {})
+else:
+next = False
+if f.null is not None:
+new_nullable = f.null
+else:
+new_nullable = None
+for dupe_opts, dupe_col in dupe_set:
+self.update_dupe_avoidance(dupe_opts, dupe_col, alias)
+self.fill_related_selections(f.rel.to._meta, alias, cur_depth + 1,
+used, next, restricted, new_nullable, dupe_set, avoid)
+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.keys()):
+# 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
+alias = truncate_name(alias, self.connection.ops.max_name_length())
+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 (value == '' and lookup_type == 'exact' and
+connection.features.interprets_empty_strings_as_nulls):
+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:
+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
+elif 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
+entry = self.where_class()
+entry.add((Constraint(alias, col, None), 'isnull', True), AND)
+entry.negate()
+self.where.add(entry, 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()
+if isinstance(child, Node):
+self.where.start_subtree(connector)
+self.add_q(child, used_aliases)
+self.where.end_subtree()
+else:
+self.add_filter(child, connector, q_object.negated,
+can_reuse=used_aliases)
+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, self.connection)
+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 = []
+if self.connection.features.allows_group_by_pk:
+if len(self.select) == len(self.model._meta.fields):
+self.group_by.append((self.model._meta.db_table,
+self.model._meta.pk.column))
+return
+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:
+self.extra_where += tuple(where)
+if params:
+self.extra_params += tuple(params)
+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 execute_sql(self, result_type=MULTI):
+"""
+Run the query against the database and returns the result(s). The
+return value is a single data item if result_type is SINGLE, or an
+iterator over the results if the result_type is MULTI.
+result_type is either MULTI (use fetchmany() to retrieve all rows),
+SINGLE (only retrieve a single row), or None. In this last case, the
+cursor is returned if any query is executed, since it's used by
+subclasses such as InsertQuery). It's possible, however, that no query
+is needed, as the filters describe an empty set. In that case, None is
+returned, to avoid any unnecessary database interaction.
+"""
+try:
+sql, params = self.as_sql()
+if not sql:
+raise EmptyResultSet
+except EmptyResultSet:
+if result_type == MULTI:
+return empty_iter()
+else:
+return
+cursor = self.connection.cursor()
+cursor.execute(sql, params)
+if not result_type:
+return cursor
+if result_type == SINGLE:
+if self.ordering_aliases:
+return cursor.fetchone()[:-len(self.ordering_aliases)]
+return cursor.fetchone()
+# The MULTI case.
+if self.ordering_aliases:
+result = order_modified_iter(cursor, len(self.ordering_aliases),
+self.connection.features.empty_fetchmany_value)
+else:
+result = iter((lambda: cursor.fetchmany(GET_ITERATOR_CHUNK_SIZE)),
+self.connection.features.empty_fetchmany_value)
+if not self.connection.features.can_use_chunked_reads:
+# If we are using non-chunked reads, we return the same data
+# structure as normally, but ensure it is all read into memory
+# before going any further.
+return list(result)
+return result
+# Use the backend's custom Query class if it defines one. Otherwise, use the
+# default.
+if connection.features.uses_custom_query_class:
+Query = connection.ops.query_class(BaseQuery)
+else:
+Query = BaseQuery
+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 empty_iter():
+"""
+Returns an iterator containing no results.
+"""
+yield iter([]).next()
+def order_modified_iter(cursor, trim, sentinel):
+"""
+Yields blocks of rows from a cursor. We use this iterator in the special
+case when extra output columns have been added to support ordering
+requirements. We must trim those extra columns before anything else can use
+the results, since they're only needed to make the SQL valid.
+"""
+for rows in iter((lambda: cursor.fetchmany(GET_ITERATOR_CHUNK_SIZE)),
+sentinel):
+yield [r[:-trim] for r in rows]
+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

changeset 0	0d40e90630ef
child 29	cc9b7e14412b