""" 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 collections import OrderedDict import copy from django.utils.encoding import force_text from django.utils.tree import Node from django.utils import six from django.db import connections, DEFAULT_DB_ALIAS from django.db.models.constants import LOOKUP_SEP from django.db.models.aggregates import refs_aggregate from django.db.models.expressions import ExpressionNode from django.db.models.fields import FieldDoesNotExist from django.db.models.query_utils import Q from django.db.models.related import PathInfo from django.db.models.sql import aggregates as base_aggregates_module from django.db.models.sql.constants import (QUERY_TERMS, ORDER_DIR, SINGLE, ORDER_PATTERN, JoinInfo, SelectInfo) from django.db.models.sql.datastructures import EmptyResultSet, Empty, MultiJoin, Col from django.db.models.sql.expressions import SQLEvaluator from django.db.models.sql.where import (WhereNode, Constraint, EverythingNode, ExtraWhere, AND, OR, EmptyWhere) from django.core.exceptions import FieldError __all__ = ['Query', 'RawQuery'] class RawQuery(object): """ A single raw SQL query """ def __init__(self, sql, using, params=None): self.params = params or () self.sql = sql self.using = using self.cursor = None # Mirror some properties of a normal query so that # the compiler can be used to process results. self.low_mark, self.high_mark = 0, None # Used for offset/limit self.extra_select = {} self.aggregate_select = {} def clone(self, using): return RawQuery(self.sql, using, params=self.params) def convert_values(self, value, field, connection): """Convert the database-returned value into a type that is consistent across database backends. By default, this defers to the underlying backend operations, but it can be overridden by Query classes for specific backends. """ return connection.ops.convert_values(value, field) def get_columns(self): if self.cursor is None: self._execute_query() converter = connections[self.using].introspection.table_name_converter return [converter(column_meta[0]) for column_meta in self.cursor.description] def __iter__(self): # Always execute a new query for a new iterator. # This could be optimized with a cache at the expense of RAM. self._execute_query() if not connections[self.using].features.can_use_chunked_reads: # If the database can't use chunked reads we need to make sure we # evaluate the entire query up front. result = list(self.cursor) else: result = self.cursor return iter(result) def __repr__(self): return "" % (self.sql % tuple(self.params)) def _execute_query(self): self.cursor = connections[self.using].cursor() self.cursor.execute(self.sql, self.params) class Query(object): """ A single SQL query. """ # SQL join types. These are part of the class because their string forms # vary from database to database and can be customised by a subclass. INNER = 'INNER JOIN' LOUTER = 'LEFT OUTER JOIN' alias_prefix = 'T' subq_aliases = frozenset([alias_prefix]) query_terms = QUERY_TERMS aggregates_module = base_aggregates_module compiler = 'SQLCompiler' def __init__(self, model, where=WhereNode): self.model = model self.alias_refcount = {} # alias_map is the most important data structure regarding joins. # It's used for recording which joins exist in the query and what # type they are. The key is the alias of the joined table (possibly # the table name) and the value is JoinInfo from constants.py. self.alias_map = {} self.table_map = {} # Maps table names to list of aliases. self.join_map = {} self.default_cols = True self.default_ordering = True self.standard_ordering = True self.used_aliases = set() self.filter_is_sticky = False self.included_inherited_models = {} # SQL-related attributes # Select and related select clauses as SelectInfo instances. # The select is used for cases where we want to set up the select # clause to contain other than default fields (values(), annotate(), # subqueries...) self.select = [] # The related_select_cols is used for columns needed for # select_related - this is populated in compile stage. self.related_select_cols = [] 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.distinct_fields = [] self.select_for_update = False self.select_for_update_nowait = False self.select_related = False # SQL aggregate-related attributes # The _aggregates will be an OrderedDict when used. Due to the cost # of creating OrderedDict this attribute is created lazily (in # self.aggregates property). self._aggregates = None # 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. # The _extra attribute is an OrderedDict, lazily created similarly to # .aggregates self._extra = None # Maps col_alias -> (col_sql, params). self.extra_select_mask = None self._extra_select_cache = None self.extra_tables = () self.extra_order_by = () # A tuple that is a set of model field names and either True, if these # are the fields to defer, or False if these are the only fields to # load. self.deferred_loading = (set(), True) @property def extra(self): if self._extra is None: self._extra = OrderedDict() return self._extra @property def aggregates(self): if self._aggregates is None: self._aggregates = OrderedDict() return self._aggregates def __str__(self): """ Returns the query as a string of SQL with the parameter values substituted in (use sql_with_params() to see the unsubstituted string). Parameter values won't necessarily be quoted correctly, since that is done by the database interface at execution time. """ sql, params = self.sql_with_params() return sql % params def sql_with_params(self): """ Returns the query as an SQL string and the parameters that will be subsituted into the query. """ return self.get_compiler(DEFAULT_DB_ALIAS).as_sql() def __deepcopy__(self, memo): result = self.clone(memo=memo) memo[id(self)] = result return result def prepare(self): return self def get_compiler(self, using=None, connection=None): if using is None and connection is None: raise ValueError("Need either using or connection") if using: connection = connections[using] # Check that the compiler will be able to execute the query for alias, aggregate in self.aggregate_select.items(): connection.ops.check_aggregate_support(aggregate) return connection.ops.compiler(self.compiler)(self, connection, using) def get_meta(self): """ Returns the Options instance (the model._meta) from which to start processing. Normally, this is self.model._meta, but it can be changed by subclasses. """ return self.model._meta def clone(self, klass=None, memo=None, **kwargs): """ Creates a copy of the current instance. The 'kwargs' parameter can be used by clients to update attributes after copying has taken place. """ obj = Empty() obj.__class__ = klass or self.__class__ obj.model = self.model obj.alias_refcount = self.alias_refcount.copy() obj.alias_map = self.alias_map.copy() obj.table_map = self.table_map.copy() obj.join_map = self.join_map.copy() obj.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.select = self.select[:] obj.related_select_cols = [] obj.tables = self.tables[:] obj.where = self.where.clone() 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 = self.having.clone() obj.order_by = self.order_by[:] obj.low_mark, obj.high_mark = self.low_mark, self.high_mark obj.distinct = self.distinct obj.distinct_fields = self.distinct_fields[:] obj.select_for_update = self.select_for_update obj.select_for_update_nowait = self.select_for_update_nowait obj.select_related = self.select_related obj.related_select_cols = [] obj._aggregates = self._aggregates.copy() if self._aggregates is not None else None if self.aggregate_select_mask is None: obj.aggregate_select_mask = None else: obj.aggregate_select_mask = self.aggregate_select_mask.copy() # _aggregate_select_cache cannot be copied, as doing so breaks the # (necessary) state in which both aggregates and # _aggregate_select_cache point to the same underlying objects. # It will get re-populated in the cloned queryset the next time it's # used. obj._aggregate_select_cache = None obj.max_depth = self.max_depth obj._extra = self._extra.copy() if self._extra is not None else None if self.extra_select_mask is None: obj.extra_select_mask = None else: obj.extra_select_mask = self.extra_select_mask.copy() if self._extra_select_cache is None: obj._extra_select_cache = None else: obj._extra_select_cache = self._extra_select_cache.copy() obj.extra_tables = self.extra_tables obj.extra_order_by = self.extra_order_by obj.deferred_loading = copy.copy(self.deferred_loading[0]), self.deferred_loading[1] 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 if 'alias_prefix' in self.__dict__: obj.alias_prefix = self.alias_prefix if 'subq_aliases' in self.__dict__: obj.subq_aliases = self.subq_aliases.copy() obj.__dict__.update(kwargs) if hasattr(obj, '_setup_query'): obj._setup_query() return obj def convert_values(self, value, field, connection): """Convert the database-returned value into a type that is consistent across database backends. By default, this defers to the underlying backend operations, but it can be overridden by Query classes for specific backends. """ return connection.ops.convert_values(value, field) def resolve_aggregate(self, value, aggregate, connection): """Resolve the value of aggregates returned by the database to consistent (and reasonable) types. This is required because of the predisposition of certain backends to return Decimal and long types when they are not needed. """ if value is None: if aggregate.is_ordinal: return 0 # Return None as-is return value elif aggregate.is_ordinal: # Any ordinal aggregate (e.g., count) returns an int return int(value) elif aggregate.is_computed: # Any computed aggregate (e.g., avg) returns a float return float(value) else: # Return value depends on the type of the field being processed. return self.convert_values(value, aggregate.field, connection) def get_aggregation(self, using, force_subq=False): """ 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 or force_subq: from django.db.models.sql.subqueries import AggregateQuery query = AggregateQuery(self.model) obj = self.clone() if not force_subq: # In forced subq case the ordering and limits will likely # affect the results. obj.clear_ordering(True) obj.clear_limits() obj.select_for_update = False obj.select_related = False obj.related_select_cols = [] relabels = dict((t, 'subquery') for t in self.tables) # 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.aggregates[alias] = aggregate.relabeled_clone(relabels) del obj.aggregate_select[alias] try: query.add_subquery(obj, using) except EmptyResultSet: return dict( (alias, None) for alias in query.aggregate_select ) else: query = self self.select = [] self.default_cols = False self._extra = {} self.remove_inherited_models() query.clear_ordering(True) query.clear_limits() query.select_for_update = False query.select_related = False query.related_select_cols = [] result = query.get_compiler(using).execute_sql(SINGLE) if result is None: result = [None for q in query.aggregate_select.items()] return dict( (alias, self.resolve_aggregate(val, aggregate, connection=connections[using])) for (alias, aggregate), val in zip(query.aggregate_select.items(), result) ) def get_count(self, using): """ Performs a COUNT() query using the current filter constraints. """ obj = self.clone() if len(self.select) > 1 or self.aggregate_select or (self.distinct and self.distinct_fields): # If a select clause exists, then the query has already started to # specify the columns that are to be returned. # In this case, we need to use a subquery to evaluate the count. from django.db.models.sql.subqueries import AggregateQuery subquery = obj subquery.clear_ordering(True) subquery.clear_limits() obj = AggregateQuery(obj.model) try: obj.add_subquery(subquery, using=using) except EmptyResultSet: # add_subquery evaluates the query, if it's an EmptyResultSet # then there are can be no results, and therefore there the # count is obviously 0 return 0 obj.add_count_column() number = obj.get_aggregation(using=using)[None] # Apply offset and limit constraints manually, since using LIMIT/OFFSET # in SQL (in variants that provide them) doesn't change the COUNT # output. number = max(0, number - self.low_mark) if self.high_mark is not None: number = min(number, self.high_mark - self.low_mark) return number def has_results(self, using): q = self.clone() if not q.distinct: q.clear_select_clause() q.clear_ordering(True) q.set_limits(high=1) compiler = q.get_compiler(using=using) return compiler.has_results() 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." assert self.distinct_fields == rhs.distinct_fields, \ "Cannot combine queries with different distinct fields." self.remove_inherited_models() # Work out how to relabel the rhs aliases, if necessary. change_map = {} conjunction = (connector == AND) # Determine which existing joins can be reused. When combining the # query with AND we must recreate all joins for m2m filters. When # combining with OR we can reuse joins. The reason is that in AND # case a single row can't fulfill a condition like: # revrel__col=1 & revrel__col=2 # But, there might be two different related rows matching this # condition. In OR case a single True is enough, so single row is # enough, too. # # Note that we will be creating duplicate joins for non-m2m joins in # the AND case. The results will be correct but this creates too many # joins. This is something that could be fixed later on. reuse = set() if conjunction else set(self.tables) # Base table must be present in the query - this is the same # table on both sides. self.get_initial_alias() joinpromoter = JoinPromoter(connector, 2) joinpromoter.add_votes( j for j in self.alias_map if self.alias_map[j].join_type == self.INNER) rhs_votes = set() # Now, add the joins from rhs query into the new query (skipping base # table). for alias in rhs.tables[1:]: table, _, join_type, lhs, join_cols, nullable, join_field = rhs.alias_map[alias] # If the left side of the join was already relabeled, use the # updated alias. lhs = change_map.get(lhs, lhs) new_alias = self.join( (lhs, table, join_cols), reuse=reuse, nullable=nullable, join_field=join_field) if join_type == self.INNER: rhs_votes.add(new_alias) # We can't reuse the same join again in the query. If we have two # distinct joins for the same connection in rhs query, then the # combined query must have two joins, too. reuse.discard(new_alias) change_map[alias] = new_alias if not rhs.alias_refcount[alias]: # The alias was unused in the rhs query. Unref it so that it # will be unused in the new query, too. We have to add and # unref the alias so that join promotion has information of # the join type for the unused alias. self.unref_alias(new_alias) joinpromoter.add_votes(rhs_votes) joinpromoter.update_join_types(self) # Now relabel a copy of the rhs where-clause and add it to the current # one. if rhs.where: w = rhs.where.clone() 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, field in rhs.select: if isinstance(col, (list, tuple)): new_col = change_map.get(col[0], col[0]), col[1] self.select.append(SelectInfo(new_col, field)) else: new_col = col.relabeled_clone(change_map) self.select.append(SelectInfo(new_col, field)) if connector == OR: # It would be nice to be able to handle this, but the queries don't # really make sense (or return consistent value sets). Not worth # the extra complexity when you can write a real query instead. if self._extra and rhs._extra: raise ValueError("When merging querysets using 'or', you " "cannot have extra(select=...) on both sides.") self.extra.update(rhs.extra) extra_select_mask = set() if self.extra_select_mask is not None: extra_select_mask.update(self.extra_select_mask) if rhs.extra_select_mask is not None: extra_select_mask.update(rhs.extra_select_mask) if extra_select_mask: self.set_extra_mask(extra_select_mask) self.extra_tables += rhs.extra_tables # Ordering uses the 'rhs' ordering, unless it has none, in which case # the current ordering is used. self.order_by = rhs.order_by[:] if rhs.order_by else self.order_by self.extra_order_by = rhs.extra_order_by or self.extra_order_by def deferred_to_data(self, target, callback): """ Converts the self.deferred_loading data structure to an alternate data structure, describing the field that *will* be loaded. This is used to compute the columns to select from the database and also by the QuerySet class to work out which fields are being initialised on each model. Models that have all their fields included aren't mentioned in the result, only those that have field restrictions in place. The "target" parameter is the instance that is populated (in place). The "callback" is a function that is called whenever a (model, field) pair need to be added to "target". It accepts three parameters: "target", and the model and list of fields being added for that model. """ field_names, defer = self.deferred_loading if not field_names: return orig_opts = self.get_meta() seen = {} must_include = {orig_opts.concrete_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] if is_reverse_o2o(source): cur_model = source.model else: cur_model = source.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 # (if it's not a reverse relation) to the things we select. if not is_reverse_o2o(source): 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 if not is_reverse_o2o(field): 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 six.iteritems(seen): for field, m in model._meta.get_fields_with_model(): if field in values: continue add_to_dict(workset, m or model, field) for model, values in six.iteritems(must_include): # 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 six.iteritems(workset): callback(target, model, values) else: for model, values in six.iteritems(must_include): 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 six.iteritems(seen): callback(target, model, values) def deferred_to_columns_cb(self, target, model, fields): """ Callback used by deferred_to_columns(). The "target" parameter should be a set instance. """ table = model._meta.db_table if table not in target: target[table] = set() for field in fields: target[table].add(field.column) def table_alias(self, table_name, create=False): """ Returns a table alias for the given table_name and whether this is a new alias or not. If 'create' is true, a new alias is always created. Otherwise, the most recently created alias for the table (if one exists) is reused. """ current = self.table_map.get(table_name) if not create and current: alias = current[0] self.alias_refcount[alias] += 1 return alias, False # Create a new alias for this table. if current: alias = '%s%d' % (self.alias_prefix, len(self.alias_map) + 1) current.append(alias) else: # The first occurence of a table uses the table name directly. alias = table_name self.table_map[alias] = [alias] self.alias_refcount[alias] = 1 self.tables.append(alias) return alias, True def ref_alias(self, alias): """ Increases the reference count for this alias. """ self.alias_refcount[alias] += 1 def unref_alias(self, alias, amount=1): """ Decreases the reference count for this alias. """ self.alias_refcount[alias] -= amount def promote_joins(self, aliases): """ Promotes recursively the join type of given aliases and its children to an outer join. If 'unconditional' is False, the join is only promoted if it is nullable or the parent join is an outer join. The children promotion is done to avoid join chains that contain a LOUTER b INNER c. So, if we have currently a INNER b INNER c and a->b is promoted, then we must also promote b->c automatically, or otherwise the promotion of a->b doesn't actually change anything in the query results. """ aliases = list(aliases) while aliases: alias = aliases.pop(0) if self.alias_map[alias].join_cols[0][1] is None: # This is the base table (first FROM entry) - this table # isn't really joined at all in the query, so we should not # alter its join type. continue # Only the first alias (skipped above) should have None join_type assert self.alias_map[alias].join_type is not None parent_alias = self.alias_map[alias].lhs_alias parent_louter = ( parent_alias and self.alias_map[parent_alias].join_type == self.LOUTER) already_louter = self.alias_map[alias].join_type == self.LOUTER if ((self.alias_map[alias].nullable or parent_louter) and not already_louter): data = self.alias_map[alias]._replace(join_type=self.LOUTER) self.alias_map[alias] = data # Join type of 'alias' changed, so re-examine all aliases that # refer to this one. aliases.extend( join for join in self.alias_map.keys() if (self.alias_map[join].lhs_alias == alias and join not in aliases)) def demote_joins(self, aliases): """ Change join type from LOUTER to INNER for all joins in aliases. Similarly to promote_joins(), this method must ensure no join chains containing first an outer, then an inner join are generated. If we are demoting b->c join in chain a LOUTER b LOUTER c then we must demote a->b automatically, or otherwise the demotion of b->c doesn't actually change anything in the query results. . """ aliases = list(aliases) while aliases: alias = aliases.pop(0) if self.alias_map[alias].join_type == self.LOUTER: self.alias_map[alias] = self.alias_map[alias]._replace(join_type=self.INNER) parent_alias = self.alias_map[alias].lhs_alias if self.alias_map[parent_alias].join_type == self.INNER: aliases.append(parent_alias) def reset_refcounts(self, to_counts): """ This method will reset reference counts for aliases so that they match the value passed in :param to_counts:. """ for alias, cur_refcount in self.alias_refcount.copy().items(): unref_amount = cur_refcount - to_counts.get(alias, 0) self.unref_alias(alias, unref_amount) 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() def relabel_column(col): if isinstance(col, (list, tuple)): old_alias = col[0] return (change_map.get(old_alias, old_alias), col[1]) else: return col.relabeled_clone(change_map) # 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) if self.group_by: self.group_by = [relabel_column(col) for col in self.group_by] self.select = [SelectInfo(relabel_column(s.col), s.field) for s in self.select] if self._aggregates: self._aggregates = OrderedDict( (key, relabel_column(col)) for key, col in self._aggregates.items()) # 2. Rename the alias in the internal table/alias datastructures. for ident, aliases in self.join_map.items(): del self.join_map[ident] aliases = tuple(change_map.get(a, a) for a in aliases) ident = (change_map.get(ident[0], ident[0]),) + ident[1:] self.join_map[ident] = aliases for old_alias, new_alias in six.iteritems(change_map): alias_data = self.alias_map[old_alias] alias_data = alias_data._replace(rhs_alias=new_alias) self.alias_refcount[new_alias] = self.alias_refcount[old_alias] del self.alias_refcount[old_alias] self.alias_map[new_alias] = 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 six.iteritems(self.alias_map): lhs = data.lhs_alias if lhs in change_map: data = data._replace(lhs_alias=change_map[lhs]) self.alias_map[alias] = data def bump_prefix(self, outer_query): """ Changes the alias prefix to the next letter in the alphabet in a way that the outer query's aliases and this query's aliases will not conflict. Even tables that previously had no alias will get an alias after this call. """ if self.alias_prefix != outer_query.alias_prefix: # No clashes between self and outer query should be possible. return self.alias_prefix = chr(ord(self.alias_prefix) + 1) while self.alias_prefix in self.subq_aliases: self.alias_prefix = chr(ord(self.alias_prefix) + 1) assert self.alias_prefix < 'Z' self.subq_aliases = self.subq_aliases.union([self.alias_prefix]) outer_query.subq_aliases = outer_query.subq_aliases.union(self.subq_aliases) change_map = OrderedDict() for pos, alias in enumerate(self.tables): new_alias = '%s%d' % (self.alias_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.get_meta().db_table, None)) return alias def count_active_tables(self): """ Returns the number of tables in this query with a non-zero reference count. Note that after execution, the reference counts are zeroed, so tables added in compiler will not be seen by this method. """ return len([1 for count in self.alias_refcount.values() if count]) def join(self, connection, reuse=None, nullable=False, join_field=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, join_cols) where 'lhs' is either an existing table alias or a table name. 'join_cols' is a tuple of tuples containing columns to join on ((l_id1, r_id1), (l_id2, r_id2)). The join corresponds to the SQL equivalent of:: lhs.l_id1 = table.r_id1 AND lhs.l_id2 = table.r_id2 The 'reuse' parameter can be either None which means all joins (matching the connection) are reusable, or it can be a set containing the aliases that can be reused. A join is always created as LOUTER if the lhs alias is LOUTER to make sure we do not generate chains like t1 LOUTER t2 INNER t3. All new joins are created as LOUTER if nullable is True. If 'nullable' is True, the join can potentially involve NULL values and is a candidate for promotion (to "left outer") when combining querysets. The 'join_field' is the field we are joining along (if any). """ lhs, table, join_cols = connection assert lhs is None or join_field is not None existing = self.join_map.get(connection, ()) if reuse is None: reuse = existing else: reuse = [a for a in existing if a in reuse] for alias in reuse: if join_field and self.alias_map[alias].join_field != join_field: # The join_map doesn't contain join_field (mainly because # fields in Query structs are problematic in pickling), so # check that the existing join is created using the same # join_field used for the under work join. continue self.ref_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 self.alias_map[lhs].join_type == self.LOUTER or nullable: join_type = self.LOUTER else: join_type = self.INNER join = JoinInfo(table, alias, join_type, lhs, join_cols or ((None, None),), nullable, join_field) self.alias_map[alias] = join if connection in self.join_map: self.join_map[connection] += (alias,) else: self.join_map[connection] = (alias,) 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.get_meta() root_alias = self.tables[0] seen = {None: root_alias} for field, model in opts.get_fields_with_model(): if model not in seen: self.join_parent_model(opts, model, root_alias, seen) self.included_inherited_models = seen def join_parent_model(self, opts, model, alias, seen): """ Makes sure the given 'model' is joined in the query. If 'model' isn't a parent of 'opts' or if it is None this method is a no-op. The 'alias' is the root alias for starting the join, 'seen' is a dict of model -> alias of existing joins. It must also contain a mapping of None -> some alias. This will be returned in the no-op case. """ if model in seen: return seen[model] chain = opts.get_base_chain(model) if chain is None: return alias curr_opts = opts for int_model in chain: if int_model in seen: return seen[int_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 curr_opts.parents[int_model]: curr_opts = int_model._meta continue link_field = curr_opts.get_ancestor_link(int_model) _, _, _, joins, _ = self.setup_joins( [link_field.name], curr_opts, alias) curr_opts = int_model._meta alias = seen[int_model] = joins[-1] return alias or seen[None] def remove_inherited_models(self): """ Undoes the effects of setup_inherited_models(). Should be called whenever select columns (self.select) are set explicitly. """ for key, alias in self.included_inherited_models.items(): if key: self.unref_alias(alias) self.included_inherited_models = {} def add_aggregate(self, aggregate, model, alias, is_summary): """ Adds a single aggregate expression to the Query """ opts = model._meta field_list = aggregate.lookup.split(LOOKUP_SEP) if len(field_list) == 1 and self._aggregates and aggregate.lookup in self.aggregates: # Aggregate is over an annotation field_name = field_list[0] col = field_name source = self.aggregates[field_name] if not is_summary: raise FieldError("Cannot compute %s('%s'): '%s' is an aggregate" % ( aggregate.name, field_name, field_name)) elif ((len(field_list) > 1) or (field_list[0] not in [i.name for i in opts.fields]) or self.group_by is None or not is_summary): # If: # - the field descriptor has more than one part (foo__bar), or # - the field descriptor is referencing an m2m/m2o field, or # - this is a reference to a model field (possibly inherited), or # - this is an annotation over a model field # then we need to explore the joins that are required. # Join promotion note - we must not remove any rows here, so use # outer join if there isn't any existing join. field, sources, opts, join_list, path = self.setup_joins( field_list, opts, self.get_initial_alias()) # Process the join chain to see if it can be trimmed targets, _, join_list = self.trim_joins(sources, join_list, path) col = targets[0].column source = sources[0] 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 # We want to have the alias in SELECT clause even if mask is set. self.append_aggregate_mask([alias]) # Add the aggregate to the query aggregate.add_to_query(self, alias, col=col, source=source, is_summary=is_summary) def prepare_lookup_value(self, value, lookup_type, can_reuse): # Interpret '__exact=None' as the sql 'is NULL'; otherwise, reject all # uses of None as a query value. if value is None: if lookup_type != 'exact': raise ValueError("Cannot use None as a query value") lookup_type = 'isnull' value = True elif callable(value): value = value() elif isinstance(value, ExpressionNode): # If value is a query expression, evaluate it value = SQLEvaluator(value, self, reuse=can_reuse) if hasattr(value, 'query') and hasattr(value.query, 'bump_prefix'): value = value._clone() value.query.bump_prefix(self) if hasattr(value, 'bump_prefix'): value = value.clone() value.bump_prefix(self) # For Oracle '' is equivalent to null. The check needs to be done # at this stage because join promotion can't be done at compiler # stage. Using DEFAULT_DB_ALIAS isn't nice, but it is the best we # can do here. Similar thing is done in is_nullable(), too. if (connections[DEFAULT_DB_ALIAS].features.interprets_empty_strings_as_nulls and lookup_type == 'exact' and value == ''): value = True lookup_type = 'isnull' return value, lookup_type def solve_lookup_type(self, lookup): """ Solve the lookup type from the lookup (eg: 'foobar__id__icontains') """ lookup_type = 'exact' # Default lookup type lookup_parts = lookup.split(LOOKUP_SEP) num_parts = len(lookup_parts) if (len(lookup_parts) > 1 and lookup_parts[-1] in self.query_terms and (not self._aggregates or lookup not in self._aggregates)): # Traverse the lookup query to distinguish related fields from # lookup types. lookup_model = self.model for counter, field_name in enumerate(lookup_parts): try: lookup_field = lookup_model._meta.get_field(field_name) except FieldDoesNotExist: # Not a field. Bail out. lookup_type = lookup_parts.pop() break # Unless we're at the end of the list of lookups, let's attempt # to continue traversing relations. if (counter + 1) < num_parts: try: lookup_model = lookup_field.rel.to except AttributeError: # Not a related field. Bail out. lookup_type = lookup_parts.pop() break return lookup_type, lookup_parts def build_filter(self, filter_expr, branch_negated=False, current_negated=False, can_reuse=None, connector=AND): """ Builds a WhereNode for a single filter clause, but doesn't add it to this Query. Query.add_q() will then add this filter to the where or having Node. The 'branch_negated' tells us if the current branch contains any negations. This will be used to determine if subqueries are needed. The 'current_negated' is used to determine if the current filter is negated or not and this will be used to determine if IS NULL filtering is needed. The difference between current_netageted and branch_negated is that branch_negated is set on first negation, but current_negated is flipped for each negation. Note that add_filter will not do any negating itself, that is done upper in the code by add_q(). The 'can_reuse' is a set of reusable joins for multijoins. The method will create a filter clause that can be added to the current query. However, if the filter isn't added to the query then the caller is responsible for unreffing the joins used. """ arg, value = filter_expr lookup_type, parts = self.solve_lookup_type(arg) if not parts: raise FieldError("Cannot parse keyword query %r" % arg) # Work out the lookup type and remove it from the end of 'parts', # if necessary. value, lookup_type = self.prepare_lookup_value(value, lookup_type, can_reuse) used_joins = getattr(value, '_used_joins', []) clause = self.where_class() if self._aggregates: for alias, aggregate in self.aggregates.items(): if alias in (parts[0], LOOKUP_SEP.join(parts)): clause.add((aggregate, lookup_type, value), AND) return clause, [] opts = self.get_meta() alias = self.get_initial_alias() allow_many = not branch_negated try: field, sources, opts, join_list, path = self.setup_joins( parts, opts, alias, can_reuse, allow_many) except MultiJoin as e: return self.split_exclude(filter_expr, LOOKUP_SEP.join(parts[:e.level]), can_reuse, e.names_with_path) if can_reuse is not None: can_reuse.update(join_list) used_joins = set(used_joins).union(set(join_list)) # Process the join list to see if we can remove any non-needed joins from # the far end (fewer tables in a query is better). targets, alias, join_list = self.trim_joins(sources, join_list, path) if hasattr(field, 'get_lookup_constraint'): constraint = field.get_lookup_constraint(self.where_class, alias, targets, sources, lookup_type, value) else: constraint = (Constraint(alias, targets[0].column, field), lookup_type, value) clause.add(constraint, AND) require_outer = lookup_type == 'isnull' and value is True and not current_negated if current_negated and (lookup_type != 'isnull' or value is False): require_outer = True if (lookup_type != 'isnull' and ( self.is_nullable(targets[0]) or self.alias_map[join_list[-1]].join_type == self.LOUTER)): # The condition added here will be SQL like this: # NOT (col IS NOT NULL), where the first NOT is added in # upper layers of code. The reason for addition is that if col # is null, then col != someval will result in SQL "unknown" # which isn't the same as in Python. The Python None handling # is wanted, and it can be gotten by # (col IS NULL OR col != someval) # <=> # NOT (col IS NOT NULL AND col = someval). clause.add((Constraint(alias, targets[0].column, None), 'isnull', False), AND) return clause, used_joins if not require_outer else () def add_filter(self, filter_clause): self.add_q(Q(**{filter_clause[0]: filter_clause[1]})) def need_having(self, obj): """ Returns whether or not all elements of this q_object need to be put together in the HAVING clause. """ if not self._aggregates: return False if not isinstance(obj, Node): return (refs_aggregate(obj[0].split(LOOKUP_SEP), self.aggregates) or (hasattr(obj[1], 'contains_aggregate') and obj[1].contains_aggregate(self.aggregates))) return any(self.need_having(c) for c in obj.children) def split_having_parts(self, q_object, negated=False): """ Returns a list of q_objects which need to go into the having clause instead of the where clause. Removes the splitted out nodes from the given q_object. Note that the q_object is altered, so cloning it is needed. """ having_parts = [] for c in q_object.children[:]: # When constucting the having nodes we need to take care to # preserve the negation status from the upper parts of the tree if isinstance(c, Node): # For each negated child, flip the in_negated flag. in_negated = c.negated ^ negated if c.connector == OR and self.need_having(c): # A subtree starting from OR clause must go into having in # whole if any part of that tree references an aggregate. q_object.children.remove(c) having_parts.append(c) c.negated = in_negated else: having_parts.extend( self.split_having_parts(c, in_negated)[1]) elif self.need_having(c): q_object.children.remove(c) new_q = self.where_class(children=[c], negated=negated) having_parts.append(new_q) return q_object, having_parts def add_q(self, q_object): """ A preprocessor for the internal _add_q(). Responsible for splitting the given q_object into where and having parts and setting up some internal variables. """ if not self.need_having(q_object): where_part, having_parts = q_object, [] else: where_part, having_parts = self.split_having_parts( q_object.clone(), q_object.negated) # For join promotion this case is doing an AND for the added q_object # and existing conditions. So, any existing inner join forces the join # type to remain inner. Exsting outer joins can however be demoted. # (Consider case where rel_a is LOUTER and rel_a__col=1 is added - if # rel_a doesn't produce any rows, then the whole condition must fail. # So, demotion is OK. existing_inner = set( (a for a in self.alias_map if self.alias_map[a].join_type == self.INNER)) clause, require_inner = self._add_q(where_part, self.used_aliases) self.where.add(clause, AND) for hp in having_parts: clause, _ = self._add_q(hp, self.used_aliases) self.having.add(clause, AND) self.demote_joins(existing_inner) def _add_q(self, q_object, used_aliases, branch_negated=False, current_negated=False): """ Adds a Q-object to the current filter. """ connector = q_object.connector current_negated = current_negated ^ q_object.negated branch_negated = branch_negated or q_object.negated # Note that if the connector happens to match what we have already in # the tree, the add will be a no-op. target_clause = self.where_class(connector=connector, negated=q_object.negated) joinpromoter = JoinPromoter(q_object.connector, len(q_object.children)) for child in q_object.children: if isinstance(child, Node): child_clause, needed_inner = self._add_q( child, used_aliases, branch_negated, current_negated) joinpromoter.add_votes(needed_inner) else: child_clause, needed_inner = self.build_filter( child, can_reuse=used_aliases, branch_negated=branch_negated, current_negated=current_negated, connector=connector) joinpromoter.add_votes(needed_inner) target_clause.add(child_clause, connector) needed_inner = joinpromoter.update_join_types(self) return target_clause, needed_inner def names_to_path(self, names, opts, allow_many): """ Walks the names path and turns them PathInfo tuples. Note that a single name in 'names' can generate multiple PathInfos (m2m for example). 'names' is the path of names to travle, 'opts' is the model Options we start the name resolving from, 'allow_many' is as for setup_joins(). Returns a list of PathInfo tuples. In addition returns the final field (the last used join field), and target (which is a field guaranteed to contain the same value as the final field). """ path, names_with_path = [], [] for pos, name in enumerate(names): if name == 'pk': name = opts.pk.name try: field, model, direct, m2m = opts.get_field_by_name(name) except FieldDoesNotExist: available = opts.get_all_field_names() + list(self.aggregate_select) raise FieldError("Cannot resolve keyword %r into field. " "Choices are: %s" % (name, ", ".join(available))) # Check if we need any joins for concrete inheritance cases (the # field lives in parent, but we are currently in one of its # children) 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 = opts.concrete_model for int_model in opts.get_base_chain(model): if int_model is proxied_model: opts = int_model._meta else: final_field = opts.parents[int_model] targets = (final_field.rel.get_related_field(),) opts = int_model._meta path.append(PathInfo(final_field.model._meta, opts, targets, final_field, False, True)) if hasattr(field, 'get_path_info'): pathinfos = field.get_path_info() if not allow_many: for inner_pos, p in enumerate(pathinfos): if p.m2m: names_with_path.append((name, pathinfos[0:inner_pos + 1])) raise MultiJoin(pos + 1, names_with_path) last = pathinfos[-1] path.extend(pathinfos) final_field = last.join_field opts = last.to_opts targets = last.target_fields names_with_path.append((name, pathinfos)) else: # Local non-relational field. final_field = field targets = (field,) break 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 path, final_field, targets def setup_joins(self, names, opts, alias, can_reuse=None, allow_many=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 starting from), 'alias' is the alias for the table to start the joining from. The 'can_reuse' defines the reverse foreign key joins we can reuse. It can be None in which case all joins are reusable or a set of aliases that can be reused. Note that non-reverse foreign keys are always reusable when using setup_joins(). If 'allow_many' is False, then any reverse foreign key seen will generate a MultiJoin exception. Returns the final field involved in the joins, the target field (used for any 'where' constraint), the final 'opts' value, the joins and the field path travelled to generate the joins. The target field is the field containing the concrete value. Final field can be something different, for example foreign key pointing to that value. Final field is needed for example in some value conversions (convert 'obj' in fk__id=obj to pk val using the foreign key field for example). """ joins = [alias] # First, generate the path for the names path, final_field, targets = self.names_to_path( names, opts, allow_many) # Then, add the path to the query's joins. Note that we can't trim # joins at this stage - we will need the information about join type # of the trimmed joins. for pos, join in enumerate(path): opts = join.to_opts if join.direct: nullable = self.is_nullable(join.join_field) else: nullable = True connection = alias, opts.db_table, join.join_field.get_joining_columns() reuse = can_reuse if join.m2m else None alias = self.join( connection, reuse=reuse, nullable=nullable, join_field=join.join_field) joins.append(alias) if hasattr(final_field, 'field'): final_field = final_field.field return final_field, targets, opts, joins, path def trim_joins(self, targets, joins, path): """ The 'target' parameter is the final field being joined to, 'joins' is the full list of join aliases. The 'path' contain the PathInfos used to create the joins. Returns the final target field and table alias and the new active joins. We will always trim any direct join if we have the target column available already in the previous table. Reverse joins can't be trimmed as we don't know if there is anything on the other side of the join. """ joins = joins[:] for pos, info in enumerate(reversed(path)): if len(joins) == 1 or not info.direct: break join_targets = set(t.column for t in info.join_field.foreign_related_fields) cur_targets = set(t.column for t in targets) if not cur_targets.issubset(join_targets): break targets = tuple(r[0] for r in info.join_field.related_fields if r[1].column in cur_targets) self.unref_alias(joins.pop()) return targets, joins[-1], joins def split_exclude(self, filter_expr, prefix, can_reuse, names_with_path): """ 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. As an example we could have original filter ~Q(child__name='foo'). We would get here with filter_expr = child__name, prefix = child and can_reuse is a set of joins usable for filters in the original query. We will turn this into equivalent of: WHERE NOT (pk IN (SELECT parent_id FROM thetable WHERE name = 'foo' AND parent_id IS NOT NULL)) It might be worth it to consider using WHERE NOT EXISTS as that has saner null handling, and is easier for the backend's optimizer to handle. """ # Generate the inner query. query = Query(self.model) query.add_filter(filter_expr) query.clear_ordering(True) # Try to have as simple as possible subquery -> trim leading joins from # the subquery. trimmed_prefix, contains_louter = query.trim_start(names_with_path) query.remove_inherited_models() # Add extra check to make sure the selected field will not be null # since we are adding a IN clause. This prevents the # database from tripping over IN (...,NULL,...) selects and returning # nothing alias, col = query.select[0].col if self.is_nullable(query.select[0].field): query.where.add((Constraint(alias, col, query.select[0].field), 'isnull', False), AND) if alias in can_reuse: pk = query.select[0].field.model._meta.pk # Need to add a restriction so that outer query's filters are in effect for # the subquery, too. query.bump_prefix(self) query.where.add( (Constraint(query.select[0].col[0], pk.column, pk), 'exact', Col(alias, pk.column)), AND ) condition, needed_inner = self.build_filter( ('%s__in' % trimmed_prefix, query), current_negated=True, branch_negated=True, can_reuse=can_reuse) if contains_louter: or_null_condition, _ = self.build_filter( ('%s__isnull' % trimmed_prefix, True), current_negated=True, branch_negated=True, can_reuse=can_reuse) condition.add(or_null_condition, OR) # Note that the end result will be: # (outercol NOT IN innerq AND outercol IS NOT NULL) OR outercol IS NULL. # This might look crazy but due to how IN works, this seems to be # correct. If the IS NOT NULL check is removed then outercol NOT # IN will return UNKNOWN. If the IS NULL check is removed, then if # outercol IS NULL we will not match the row. return condition, needed_inner def set_empty(self): self.where = EmptyWhere() self.having = EmptyWhere() def is_empty(self): return isinstance(self.where, EmptyWhere) or isinstance(self.having, EmptyWhere) 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_clause(self): """ Removes all fields from SELECT clause. """ self.select = [] self.default_cols = False self.select_related = False self.set_extra_mask(()) self.set_aggregate_mask(()) 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 = [] def add_distinct_fields(self, *field_names): """ Adds and resolves the given fields to the query's "distinct on" clause. """ self.distinct_fields = field_names self.distinct = True 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: # Join promotion note - we must not remove any rows here, so # if there is no existing joins, use outer join. field, targets, u2, joins, path = self.setup_joins( name.split(LOOKUP_SEP), opts, alias, can_reuse=None, allow_many=allow_m2m) targets, final_alias, joins = self.trim_joins(targets, joins, path) for target in targets: self.select.append(SelectInfo((final_alias, target.column), target)) except MultiJoin: raise FieldError("Invalid field name: '%s'" % name) except FieldError: if LOOKUP_SEP in name: # For lookups spanning over relationships, show the error # from the model on which the lookup failed. raise else: names = sorted(opts.get_all_field_names() + list(self.extra) + list(self.aggregate_select)) 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): """ Removes any ordering settings. If 'force_empty' is True, there will be no ordering in the resulting query (not even the model's default). """ self.order_by = [] self.extra_order_by = () if force_empty: self.default_ordering = False def set_group_by(self): """ Expands the GROUP BY clause required by the query. This will usually be the set of all non-aggregate fields in the return data. If the database backend supports grouping by the primary key, and the query would be equivalent, the optimization will be made automatically. """ self.group_by = [] for col, _ in self.select: self.group_by.append(col) 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].col) else: opts = self.get_meta() if not self.select: count = self.aggregates_module.Count( (self.join((None, opts.db_table, 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].col, 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). """ if isinstance(self.select_related, bool): field_dict = {} else: field_dict = self.select_related 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 = [] 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 = OrderedDict() if select_params: param_iter = iter(select_params) else: param_iter = iter([]) for name, entry in select.items(): entry = force_text(entry) entry_params = [] pos = entry.find("%s") while pos != -1: entry_params.append(next(param_iter)) pos = entry.find("%s", pos + 2) select_pairs[name] = (entry, entry_params) # This is order preserving, since self.extra_select is an OrderedDict. self.extra.update(select_pairs) if where or params: self.where.add(ExtraWhere(where, params), AND) if tables: self.extra_tables += tuple(tables) if order_by: self.extra_order_by = order_by def clear_deferred_loading(self): """ Remove any fields from the deferred loading set. """ self.deferred_loading = (set(), True) def add_deferred_loading(self, field_names): """ Add the given list of model field names to the set of fields to exclude from loading from the database when automatic column selection is done. The new field names are added to any existing field names that are deferred (or removed from any existing field names that are marked as the only ones for immediate loading). """ # Fields on related models are stored in the literal double-underscore # format, so that we can use a set datastructure. We do the foo__bar # splitting and handling when computing the SQL colum names (as part of # get_columns()). existing, defer = self.deferred_loading if defer: # Add to existing deferred names. self.deferred_loading = existing.union(field_names), True else: # Remove names from the set of any existing "immediate load" names. self.deferred_loading = existing.difference(field_names), False def add_immediate_loading(self, field_names): """ Add the given list of model field names to the set of fields to retrieve when the SQL is executed ("immediate loading" fields). The field names replace any existing immediate loading field names. If there are field names already specified for deferred loading, those names are removed from the new field_names before storing the new names for immediate loading. (That is, immediate loading overrides any existing immediate values, but respects existing deferrals.) """ existing, defer = self.deferred_loading field_names = set(field_names) if 'pk' in field_names: field_names.remove('pk') field_names.add(self.get_meta().pk.name) if defer: # Remove any existing deferred names from the current set before # setting the new names. self.deferred_loading = field_names.difference(existing), False else: # Replace any existing "immediate load" field names. self.deferred_loading = 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. """ # We cache this because we call this function multiple times # (compiler.fill_related_selections, query.iterator) try: return self._loaded_field_names_cache except AttributeError: collection = {} self.deferred_to_data(collection, self.get_loaded_field_names_cb) self._loaded_field_names_cache = collection 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 append_aggregate_mask(self, names): if self.aggregate_select_mask is not None: self.set_aggregate_mask(set(names).union(self.aggregate_select_mask)) 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 @property def aggregate_select(self): """The OrderedDict 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 not self._aggregates: return {} elif self.aggregate_select_mask is not None: self._aggregate_select_cache = OrderedDict( (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 @property def extra_select(self): if self._extra_select_cache is not None: return self._extra_select_cache if not self._extra: return {} elif self.extra_select_mask is not None: self._extra_select_cache = OrderedDict( (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 def trim_start(self, names_with_path): """ Trims joins from the start of the join path. The candidates for trim are the PathInfos in names_with_path structure that are m2m joins. Also sets the select column so the start matches the join. This method is meant to be used for generating the subquery joins & cols in split_exclude(). Returns a lookup usable for doing outerq.filter(lookup=self). Returns also if the joins in the prefix contain a LEFT OUTER join. _""" all_paths = [] for _, paths in names_with_path: all_paths.extend(paths) contains_louter = False for pos, path in enumerate(all_paths): if path.m2m: break if self.alias_map[self.tables[pos + 1]].join_type == self.LOUTER: contains_louter = True self.unref_alias(self.tables[pos]) # The path.join_field is a Rel, lets get the other side's field join_field = path.join_field.field # Build the filter prefix. trimmed_prefix = [] paths_in_prefix = pos for name, path in names_with_path: if paths_in_prefix - len(path) < 0: break trimmed_prefix.append(name) paths_in_prefix -= len(path) trimmed_prefix.append( join_field.foreign_related_fields[0].name) trimmed_prefix = LOOKUP_SEP.join(trimmed_prefix) # Lets still see if we can trim the first join from the inner query # (that is, self). We can't do this for LEFT JOINs because we would # miss those rows that have nothing on the outer side. if self.alias_map[self.tables[pos + 1]].join_type != self.LOUTER: select_fields = [r[0] for r in join_field.related_fields] select_alias = self.tables[pos + 1] self.unref_alias(self.tables[pos]) extra_restriction = join_field.get_extra_restriction( self.where_class, None, self.tables[pos + 1]) if extra_restriction: self.where.add(extra_restriction, AND) else: # TODO: It might be possible to trim more joins from the start of the # inner query if it happens to have a longer join chain containing the # values in select_fields. Lets punt this one for now. select_fields = [r[1] for r in join_field.related_fields] select_alias = self.tables[pos] self.select = [SelectInfo((select_alias, f.column), f) for f in select_fields] return trimmed_prefix, contains_louter def is_nullable(self, field): """ A helper to check if the given field should be treated as nullable. Some backends treat '' as null and Django treats such fields as nullable for those backends. In such situations field.null can be False even if we should treat the field as nullable. """ # We need to use DEFAULT_DB_ALIAS here, as QuerySet does not have # (nor should it have) knowledge of which connection is going to be # used. The proper fix would be to defer all decisions where # is_nullable() is needed to the compiler stage, but that is not easy # to do currently. if ((connections[DEFAULT_DB_ALIAS].features.interprets_empty_strings_as_nulls) and field.empty_strings_allowed): return True else: return field.null 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 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 is_reverse_o2o(field): """ A little helper to check if the given field is reverse-o2o. The field is expected to be some sort of relation field or related object. """ return not hasattr(field, 'rel') and field.field.unique def alias_diff(refcounts_before, refcounts_after): """ Given the before and after copies of refcounts works out which aliases have been added to the after copy. """ # Use -1 as default value so that any join that is created, then trimmed # is seen as added. return set(t for t in refcounts_after if refcounts_after[t] > refcounts_before.get(t, -1)) class JoinPromoter(object): """ A class to abstract away join promotion problems for complex filter conditions. """ def __init__(self, connector, num_children): self.connector = connector self.num_children = num_children # Maps of table alias to how many times it is seen as required for # inner and/or outer joins. self.outer_votes = {} self.inner_votes = {} def add_votes(self, inner_votes): """ Add single vote per item to self.inner_votes. Parameter can be any iterable. """ for voted in inner_votes: self.inner_votes[voted] = self.inner_votes.get(voted, 0) + 1 def update_join_types(self, query): """ Change join types so that the generated query is as efficient as possible, but still correct. So, change as many joins as possible to INNER, but don't make OUTER joins INNER if that could remove results from the query. """ to_promote = set() to_demote = set() for table, votes in self.inner_votes.items(): # We must use outer joins in OR case when the join isn't contained # in all of the joins. Otherwise the INNER JOIN itself could remove # valid results. Consider the case where a model with rel_a and # rel_b relations is queried with rel_a__col=1 | rel_b__col=2. Now, # if rel_a join doesn't produce any results is null (for example # reverse foreign key or null value in direct foreign key), and # there is a matching row in rel_b with col=2, then an INNER join # to rel_a would remove a valid match from the query. So, we need # to promote any existing INNER to LOUTER (it is possible this # promotion in turn will be demoted later on). if self.connector == 'OR' and votes < self.num_children: to_promote.add(table) # If connector is AND and there is a filter that can match only # when there is a joinable row, then use INNER. For example, in # rel_a__col=1 & rel_b__col=2, if either of the rels produce NULL # as join output, then the col=1 or col=2 can't match (as # NULL=anything is always false). # For the OR case, if all children voted for a join to be inner, # then we can use INNER for the join. For example: # (rel_a__col__icontains=Alex | rel_a__col__icontains=Russell) # then if rel_a doesn't produce any rows, the whole condition # can't match. Hence we can safely use INNER join. if self.connector == 'AND' or (self.connector == 'OR' and votes == self.num_children): to_demote.add(table) # Finally, what happens in cases where we have: # (rel_a__col=1|rel_b__col=2) & rel_a__col__gte=0 # Now, we first generate the OR clause, and promote joins for it # in the first if branch above. Both rel_a and rel_b are promoted # to LOUTER joins. After that we do the AND case. The OR case # voted no inner joins but the rel_a__col__gte=0 votes inner join # for rel_a. We demote it back to INNER join (in AND case a single # vote is enough). The demotion is OK, if rel_a doesn't produce # rows, then the rel_a__col__gte=0 clause can't be true, and thus # the whole clause must be false. So, it is safe to use INNER # join. # Note that in this example we could just as well have the __gte # clause and the OR clause swapped. Or we could replace the __gte # clause with a OR clause containing rel_a__col=1|rel_a__col=2, # and again we could safely demote to INNER. query.promote_joins(to_promote) query.demote_joins(to_demote) return to_demote