--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/app/django/db/models/sql/query.py Fri Jul 18 18:22:23 2008 +0000
@@ -0,0 +1,1528 @@
+"""
+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.dispatch import dispatcher
+from django.db import connection
+from django.db.models import signals
+from django.db.models.sql.where import WhereNode, EverythingNode, AND, OR
+from django.db.models.sql.datastructures import Count
+from django.db.models.fields import FieldDoesNotExist
+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']
+
+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
+
+ 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.start_meta = None
+ self.select_fields = []
+ self.related_select_fields = []
+
+ # SQL-related attributes
+ self.select = []
+ self.tables = [] # Aliases in the order they are created.
+ self.where = where()
+ self.where_class = where
+ self.group_by = []
+ self.having = []
+ 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 = []
+
+ # 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_select = {} # Maps col_alias -> col_sql.
+ self.extra_select_params = ()
+ self.extra_tables = ()
+ self.extra_where = ()
+ self.extra_params = ()
+ self.extra_order_by = ()
+
+ 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()
+ del obj_dict['connection']
+ return obj_dict
+
+ def __setstate__(self, obj_dict):
+ """
+ Unpickling support.
+ """
+ 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 change.
+ """
+ if self.start_meta:
+ return self.start_meta
+ 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.ordering_aliases = []
+ obj.start_meta = self.start_meta
+ obj.select_fields = self.select_fields[:]
+ obj.related_select_fields = self.related_select_fields[:]
+ obj.select = self.select[:]
+ obj.tables = self.tables[:]
+ obj.where = deepcopy(self.where)
+ obj.where_class = self.where_class
+ obj.group_by = self.group_by[:]
+ obj.having = 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.max_depth = self.max_depth
+ obj.extra_select = self.extra_select.copy()
+ obj.extra_select_params = self.extra_select_params
+ 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.__dict__.update(kwargs)
+ if hasattr(obj, '_setup_query'):
+ obj._setup_query()
+ return obj
+
+ def results_iter(self):
+ """
+ Returns an iterator over the results from executing this query.
+ """
+ resolve_columns = hasattr(self, 'resolve_columns')
+ if resolve_columns:
+ if self.select_fields:
+ fields = self.select_fields + self.related_select_fields
+ else:
+ fields = self.model._meta.fields
+ for rows in self.execute_sql(MULTI):
+ for row in rows:
+ if resolve_columns:
+ row = self.resolve_columns(row, fields)
+ yield row
+
+ def get_count(self):
+ """
+ Performs a COUNT() query using the current filter constraints.
+ """
+ from subqueries import CountQuery
+ obj = self.clone()
+ obj.clear_ordering(True)
+ obj.clear_limits()
+ obj.select_related = False
+ obj.related_select_cols = []
+ obj.related_select_fields = []
+ if obj.distinct and len(obj.select) > 1:
+ obj = self.clone(CountQuery, _query=obj, where=self.where_class(),
+ distinct=False)
+ obj.select = []
+ obj.extra_select = {}
+ obj.add_count_column()
+ data = obj.execute_sql(SINGLE)
+ if not data:
+ return 0
+ number = data[0]
+
+ # 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:
+ 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 = 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()
+
+ where, w_params = self.where.as_sql(qn=self.quote_name_unless_alias)
+ params = list(self.extra_select_params)
+
+ 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))
+
+ if self.group_by:
+ grouping = self.get_grouping()
+ result.append('GROUP BY %s' % ', '.join(grouping))
+
+ if ordering:
+ result.append('ORDER BY %s' % ', '.join(ordering))
+
+ # FIXME: Pull this out to make life easier for Oracle et al.
+ if with_limits:
+ if self.high_mark:
+ result.append('LIMIT %d' % (self.high_mark - self.low_mark))
+ if self.low_mark:
+ if not self.high_mark:
+ 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 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."
+
+ # 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[:]
+ self.extra_select = rhs.extra_select.copy()
+ 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 self.select_related and not self.related_select_cols:
+ self.fill_related_selections()
+
+ def get_columns(self, with_aliases=False):
+ """
+ Return 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 ambiguitity with nested queries.
+ """
+ qn = self.quote_name_unless_alias
+ qn2 = self.connection.ops.quote_name
+ result = ['(%s) AS %s' % (col, 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:
+ for col in self.select:
+ if isinstance(col, (list, tuple)):
+ r = '%s.%s' % (qn(col[0]), qn(col[1]))
+ if with_aliases and 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(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)
+ 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):
+ """
+ Computes the default columns for selecting every field in the base
+ model.
+
+ Returns a list of strings, quoted appropriately for use in SQL
+ directly, as well as a set of aliases used in the select statement.
+ """
+ result = []
+ table_alias = self.tables[0]
+ root_pk = self.model._meta.pk.column
+ seen = {None: table_alias}
+ qn = self.quote_name_unless_alias
+ qn2 = self.connection.ops.quote_name
+ aliases = set()
+ for field, model in self.model._meta.get_fields_with_model():
+ try:
+ alias = seen[model]
+ except KeyError:
+ alias = self.join((table_alias, model._meta.db_table,
+ root_pk, model._meta.pk.column))
+ seen[model] = alias
+ 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", for example (e.g. CountQuery).
+
+ 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)
+ if alias not in self.alias_map:
+ 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 = []
+ for col in self.group_by:
+ 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
+
+ def get_ordering(self):
+ """
+ Returns list representing the SQL elements in the "order by" clause.
+ 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 = []
+ 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 = []
+ ordering_aliases = []
+ if self.standard_ordering:
+ asc, desc = ORDER_DIR['ASC']
+ else:
+ asc, desc = ORDER_DIR['DESC']
+ 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))
+ continue
+ if '.' in field:
+ # This came in through an extra(order_by=...) addition. Pass it
+ # on verbatim.
+ col, order = get_order_dir(field, asc)
+ table, col = col.split('.', 1)
+ elt = '%s.%s' % (qn(table), col)
+ if not distinct or elt in select_aliases:
+ result.append('%s %s' % (elt, order))
+ 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):
+ elt = '%s.%s' % (qn(table), qn2(col))
+ if distinct and elt not in select_aliases:
+ ordering_aliases.append(elt)
+ result.append('%s %s' % (elt, order))
+ else:
+ col, order = get_order_dir(field, asc)
+ elt = qn(col)
+ if distinct and elt not in select_aliases:
+ ordering_aliases.append(elt)
+ result.append('%s %s' % (elt, order))
+ self.ordering_aliases = ordering_aliases
+ return result
+
+ 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 = self.setup_joins(pieces, opts,
+ alias, False)
+ alias = joins[-1]
+ col = target.column
+
+ # 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).
+ join = self.alias_map[alias]
+ if col == join[RHS_JOIN_COL]:
+ 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.alias_map[alias] = None
+ 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.
+ """
+ if ((unconditional or self.alias_map[alias][NULLABLE]) and
+ self.alias_map[alias] != self.LOUTER):
+ data = list(self.alias_map[alias])
+ data[JOIN_TYPE] = self.LOUTER
+ self.alias_map[alias] = tuple(data)
+
+ 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" and "where".
+ self.where.relabel_aliases(change_map)
+ for pos, col in enumerate(self.select):
+ if isinstance(col, (list, tuple)):
+ self.select[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
+
+ # 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.
+ """
+ assert ord(self.alias_prefix) < ord('Z')
+ self.alias_prefix = chr(ord(self.alias_prefix) + 1)
+ change_map = {}
+ prefix = self.alias_prefix
+ 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. Otherwise
+ 'reuse' must be a set and a new join is created unless one of the
+ aliases in `reuse` can be used.
+
+ 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 for this table".
+ exclusions = set(self.table_map[table]).difference(reuse)
+ 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:
+ 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 fill_related_selections(self, opts=None, root_alias=None, cur_depth=1,
+ used=None, requested=None, restricted=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()
+
+ # 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 f.rel or (restricted and f.name not in requested) or
+ (not restricted and f.null) or f.rel.parent_link):
+ continue
+ table = f.rel.to._meta.db_table
+ if model:
+ int_opts = opts
+ alias = root_alias
+ for int_model in opts.get_base_chain(model):
+ lhs_col = int_opts.parents[int_model].column
+ int_opts = int_model._meta
+ alias = self.join((alias, int_opts.db_table, lhs_col,
+ int_opts.pk.column), exclusions=used,
+ promote=f.null)
+ else:
+ alias = root_alias
+ alias = self.join((alias, table, f.column,
+ f.rel.get_related_field().column), exclusions=used,
+ promote=f.null)
+ used.add(alias)
+ self.related_select_cols.extend([(alias, f2.column)
+ for f2 in f.rel.to._meta.fields])
+ self.related_select_fields.extend(f.rel.to._meta.fields)
+ if restricted:
+ next = requested.get(f.name, {})
+ else:
+ next = False
+ self.fill_related_selections(f.rel.to._meta, alias, cur_depth + 1,
+ used, next, restricted)
+
+ def add_filter(self, filter_expr, connector=AND, negate=False, trim=False,
+ can_reuse=None):
+ """
+ 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.
+ """
+ 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()
+
+ # 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()
+
+ opts = self.get_meta()
+ alias = self.get_initial_alias()
+ allow_many = trim or not negate
+
+ try:
+ field, target, opts, join_list, last = self.setup_joins(parts, opts,
+ alias, True, allow_many, can_reuse=can_reuse)
+ except MultiJoin, e:
+ self.split_exclude(filter_expr, LOOKUP_SEP.join(parts[:e.level]))
+ return
+ 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]
+
+ if final > 1:
+ # An optimization: if the final join is against the same column as
+ # we are comparing against, we can go back one step in the join
+ # chain and compare against the lhs of the join instead. The result
+ # (potentially) involves one less table join.
+ join = self.alias_map[alias]
+ if col == join[RHS_JOIN_COL]:
+ 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()
+
+ if (lookup_type == 'isnull' and value is True and not negate and
+ final > 1):
+ # If the comparison is against NULL, we need to use a left outer
+ # join when connecting to the previous model. We make that
+ # adjustment here. We don't do this unless needed as it's less
+ # efficient at the database level.
+ self.promote_alias(join_list[penultimate])
+
+ 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()
+ for join in join_it:
+ table = table_it.next()
+ if join == table and self.alias_refcount[join] > 1:
+ continue
+ self.promote_alias(join)
+ if table != join:
+ self.promote_alias(table)
+ break
+ for join in join_it:
+ self.promote_alias(join)
+ for table in table_it:
+ # Some of these will have been promoted from the join_list, but
+ # that's harmless.
+ self.promote_alias(table)
+
+ self.where.add((alias, col, field, lookup_type, value), connector)
+ if negate:
+ for alias in join_list:
+ self.promote_alias(alias)
+ if final > 1 and lookup_type != 'isnull':
+ for alias in join_list:
+ if self.alias_map[alias] == self.LOUTER:
+ j_col = self.alias_map[alias][RHS_JOIN_COL]
+ entry = Node([(alias, j_col, None, 'isnull', True)])
+ entry.negate()
+ self.where.add(entry, AND)
+ break
+ if can_reuse is not None:
+ can_reuse.update(join_list)
+
+ 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 = set()
+ if hasattr(q_object, 'add_to_query'):
+ # Complex custom objects are responsible for adding themselves.
+ q_object.add_to_query(self, used_aliases)
+ return
+
+ 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 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)
+ connector = q_object.connector
+ if q_object.negated:
+ self.where.negate()
+ if subtree:
+ self.where.end_subtree()
+
+ def setup_joins(self, names, opts, alias, dupe_multis, allow_many=True,
+ allow_explicit_fk=False, can_reuse=None):
+ """
+ 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).
+
+ 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]
+ for pos, name in enumerate(names):
+ 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()
+ 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.
+ alias_list = []
+ for int_model in opts.get_base_chain(model):
+ lhs_col = opts.parents[int_model].column
+ opts = int_model._meta
+ alias = self.join((alias, opts.db_table, lhs_col,
+ opts.pk.column), exclusions=joins)
+ joins.append(alias)
+ cached_data = opts._join_cache.get(name)
+ orig_opts = opts
+
+ 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, joins, nullable=True, reuse=can_reuse)
+ alias = self.join((int_alias, table2, from_col2, to_col2),
+ dupe_multis, joins, 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=joins, 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, joins, nullable=True, reuse=can_reuse)
+ alias = self.join((int_alias, table2, from_col2, to_col2),
+ dupe_multis, joins, 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, joins, nullable=True, reuse=can_reuse)
+ joins.append(alias)
+
+ if pos != len(names) - 1:
+ raise FieldError("Join on field %r not permitted." % name)
+
+ return field, target, opts, joins, last
+
+ def split_exclude(self, filter_expr, prefix):
+ """
+ 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)
+ query.set_start(prefix)
+ query.clear_ordering(True)
+ self.add_filter(('%s__in' % prefix, query), negate=True, trim=True)
+
+ 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:
+ if self.high_mark:
+ self.high_mark = min(self.high_mark, self.low_mark + high)
+ else:
+ self.high_mark = self.low_mark + high
+ if low:
+ if self.high_mark:
+ 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 or self.high_mark)
+
+ 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 = 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]
+ for join in joins[1:]:
+ # Only nullable aliases are promoted, so we don't end up
+ # doing unnecessary left outer joins here.
+ self.promote_alias(join)
+ 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_select.keys()
+ names.sort()
+ raise FieldError("Cannot resolve keyword %r into field. "
+ "Choices are: %s" % (name, ", ".join(names)))
+
+ 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 add_count_column(self):
+ """
+ Converts the query to do count(...) or count(distinct(pk)) in order to
+ get its size.
+ """
+ # TODO: When group_by support is added, this needs to be adjusted so
+ # that it doesn't totally overwrite the select list.
+ if not self.distinct:
+ if not self.select:
+ select = Count()
+ else:
+ assert len(self.select) == 1, \
+ "Cannot add count col with multiple cols in 'select': %r" % self.select
+ select = Count(self.select[0])
+ else:
+ opts = self.model._meta
+ if not self.select:
+ select = Count((self.join((None, opts.db_table, None, None)),
+ opts.pk.column), True)
+ else:
+ # Because of SQL portability issues, multi-column, distinct
+ # counts need a sub-query -- see get_count() for details.
+ assert len(self.select) == 1, \
+ "Cannot add count col with multiple cols in 'select'."
+ select = Count(self.select[0], True)
+
+ # Distinct handling is done in Count(), so don't do it at this
+ # level.
+ self.distinct = False
+ self.select = [select]
+ self.select_fields = [None]
+ self.extra_select = {}
+ self.extra_select_params = ()
+
+ 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:
+ # The extra select might be ordered (because it will be accepting
+ # parameters).
+ if (isinstance(select, SortedDict) and
+ not isinstance(self.extra_select, SortedDict)):
+ self.extra_select = SortedDict(self.extra_select)
+ self.extra_select.update(select)
+ if select_params:
+ self.extra_select_params += tuple(select_params)
+ 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 trim_extra_select(self, names):
+ """
+ Removes any aliases in the extra_select dictionary that aren't in
+ 'names'.
+
+ This is needed if we are selecting certain values that don't incldue
+ all of the extra_select names.
+ """
+ for key in set(self.extra_select).difference(set(names)):
+ del self.extra_select[key]
+
+ 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 = self.setup_joins(
+ start.split(LOOKUP_SEP), opts, alias, False)
+ alias = joins[last[-1]]
+ self.select = [(alias, self.alias_map[alias][RHS_JOIN_COL])]
+ self.select_fields = [field]
+ self.start_meta = opts
+
+ # The call to setup_joins add an extra reference to everything in
+ # joins. So we need to unref everything once, and everything prior to
+ # the final join a second time.
+ for alias in joins:
+ self.unref_alias(alias)
+ for alias in joins[:last[-1]]:
+ self.unref_alias(alias)
+
+ 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 (no results expected, but
+ the cursor is returned, since it's used by subclasses such as
+ InsertQuery).
+ """
+ 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(results.ordering_aliases)]
+ return cursor.fetchone()
+
+ # The MULTI case.
+ if self.ordering_aliases:
+ return order_modified_iter(cursor, len(self.ordering_aliases),
+ self.connection.features.empty_fetchmany_value)
+ return iter((lambda: cursor.fetchmany(GET_ITERATOR_CHUNK_SIZE)),
+ self.connection.features.empty_fetchmany_value)
+
+# 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(Query)
+
+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):
+ """
+ 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 = {}
+
+dispatcher.connect(setup_join_cache, signal=signals.class_prepared)
+