""" Code to manage the creation and SQL rendering of 'where' constraints. """ import datetime from itertools import repeat from django.utils import tree from django.db.models.fields import Field from django.db.models.query_utils import QueryWrapper from datastructures import EmptyResultSet, FullResultSet # Connection types AND = 'AND' OR = 'OR' class EmptyShortCircuit(Exception): """ Internal exception used to indicate that a "matches nothing" node should be added to the where-clause. """ pass class WhereNode(tree.Node): """ Used to represent the SQL where-clause. The class is tied to the Query class that created it (in order to create the correct SQL). The children in this tree are usually either Q-like objects or lists of [table_alias, field_name, db_type, lookup_type, value_annotation, params]. However, a child could also be any class with as_sql() and relabel_aliases() methods. """ default = AND def add(self, data, connector): """ Add a node to the where-tree. If the data is a list or tuple, it is expected to be of the form (obj, lookup_type, value), where obj is a Constraint object, and is then slightly munged before being stored (to avoid storing any reference to field objects). Otherwise, the 'data' is stored unchanged and can be any class with an 'as_sql()' method. """ if not isinstance(data, (list, tuple)): super(WhereNode, self).add(data, connector) return obj, lookup_type, value = data if hasattr(value, '__iter__') and hasattr(value, 'next'): # Consume any generators immediately, so that we can determine # emptiness and transform any non-empty values correctly. value = list(value) # The "annotation" parameter is used to pass auxilliary information # about the value(s) to the query construction. Specifically, datetime # and empty values need special handling. Other types could be used # here in the future (using Python types is suggested for consistency). if isinstance(value, datetime.datetime): annotation = datetime.datetime elif hasattr(value, 'value_annotation'): annotation = value.value_annotation else: annotation = bool(value) if hasattr(obj, "prepare"): value = obj.prepare(lookup_type, value) super(WhereNode, self).add((obj, lookup_type, annotation, value), connector) return super(WhereNode, self).add((obj, lookup_type, annotation, value), connector) def as_sql(self, qn, connection): """ Returns the SQL version of the where clause and the value to be substituted in. Returns None, None if this node is empty. If 'node' is provided, that is the root of the SQL generation (generally not needed except by the internal implementation for recursion). """ if not self.children: return None, [] result = [] result_params = [] empty = True for child in self.children: try: if hasattr(child, 'as_sql'): sql, params = child.as_sql(qn=qn, connection=connection) else: # A leaf node in the tree. sql, params = self.make_atom(child, qn, connection) except EmptyResultSet: if self.connector == AND and not self.negated: # We can bail out early in this particular case (only). raise elif self.negated: empty = False continue except FullResultSet: if self.connector == OR: if self.negated: empty = True break # We match everything. No need for any constraints. return '', [] if self.negated: empty = True continue empty = False if sql: result.append(sql) result_params.extend(params) if empty: raise EmptyResultSet conn = ' %s ' % self.connector sql_string = conn.join(result) if sql_string: if self.negated: sql_string = 'NOT (%s)' % sql_string elif len(self.children) != 1: sql_string = '(%s)' % sql_string return sql_string, result_params def make_atom(self, child, qn, connection): """ Turn a tuple (table_alias, column_name, db_type, lookup_type, value_annot, params) into valid SQL. Returns the string for the SQL fragment and the parameters to use for it. """ lvalue, lookup_type, value_annot, params_or_value = child if hasattr(lvalue, 'process'): try: lvalue, params = lvalue.process(lookup_type, params_or_value, connection) except EmptyShortCircuit: raise EmptyResultSet else: params = Field().get_db_prep_lookup(lookup_type, params_or_value, connection=connection, prepared=True) if isinstance(lvalue, tuple): # A direct database column lookup. field_sql = self.sql_for_columns(lvalue, qn, connection) else: # A smart object with an as_sql() method. field_sql = lvalue.as_sql(qn, connection) if value_annot is datetime.datetime: cast_sql = connection.ops.datetime_cast_sql() else: cast_sql = '%s' if hasattr(params, 'as_sql'): extra, params = params.as_sql(qn, connection) cast_sql = '' else: extra = '' if (len(params) == 1 and params[0] == '' and lookup_type == 'exact' and connection.features.interprets_empty_strings_as_nulls): lookup_type = 'isnull' value_annot = True if lookup_type in connection.operators: format = "%s %%s %%s" % (connection.ops.lookup_cast(lookup_type),) return (format % (field_sql, connection.operators[lookup_type] % cast_sql, extra), params) if lookup_type == 'in': if not value_annot: raise EmptyResultSet if extra: return ('%s IN %s' % (field_sql, extra), params) max_in_list_size = connection.ops.max_in_list_size() if max_in_list_size and len(params) > max_in_list_size: # Break up the params list into an OR of manageable chunks. in_clause_elements = ['('] for offset in xrange(0, len(params), max_in_list_size): if offset > 0: in_clause_elements.append(' OR ') in_clause_elements.append('%s IN (' % field_sql) group_size = min(len(params) - offset, max_in_list_size) param_group = ', '.join(repeat('%s', group_size)) in_clause_elements.append(param_group) in_clause_elements.append(')') in_clause_elements.append(')') return ''.join(in_clause_elements), params else: return ('%s IN (%s)' % (field_sql, ', '.join(repeat('%s', len(params)))), params) elif lookup_type in ('range', 'year'): return ('%s BETWEEN %%s and %%s' % field_sql, params) elif lookup_type in ('month', 'day', 'week_day'): return ('%s = %%s' % connection.ops.date_extract_sql(lookup_type, field_sql), params) elif lookup_type == 'isnull': return ('%s IS %sNULL' % (field_sql, (not value_annot and 'NOT ' or '')), ()) elif lookup_type == 'search': return (connection.ops.fulltext_search_sql(field_sql), params) elif lookup_type in ('regex', 'iregex'): return connection.ops.regex_lookup(lookup_type) % (field_sql, cast_sql), params raise TypeError('Invalid lookup_type: %r' % lookup_type) def sql_for_columns(self, data, qn, connection): """ Returns the SQL fragment used for the left-hand side of a column constraint (for example, the "T1.foo" portion in the clause "WHERE ... T1.foo = 6"). """ table_alias, name, db_type = data if table_alias: lhs = '%s.%s' % (qn(table_alias), qn(name)) else: lhs = qn(name) return connection.ops.field_cast_sql(db_type) % lhs def relabel_aliases(self, change_map, node=None): """ Relabels the alias values of any children. 'change_map' is a dictionary mapping old (current) alias values to the new values. """ if not node: node = self for pos, child in enumerate(node.children): if hasattr(child, 'relabel_aliases'): child.relabel_aliases(change_map) elif isinstance(child, tree.Node): self.relabel_aliases(change_map, child) elif isinstance(child, (list, tuple)): if isinstance(child[0], (list, tuple)): elt = list(child[0]) if elt[0] in change_map: elt[0] = change_map[elt[0]] node.children[pos] = (tuple(elt),) + child[1:] else: child[0].relabel_aliases(change_map) # Check if the query value also requires relabelling if hasattr(child[3], 'relabel_aliases'): child[3].relabel_aliases(change_map) class EverythingNode(object): """ A node that matches everything. """ def as_sql(self, qn=None, connection=None): raise FullResultSet def relabel_aliases(self, change_map, node=None): return class NothingNode(object): """ A node that matches nothing. """ def as_sql(self, qn=None, connection=None): raise EmptyResultSet def relabel_aliases(self, change_map, node=None): return class ExtraWhere(object): def __init__(self, sqls, params): self.sqls = sqls self.params = params def as_sql(self, qn=None, connection=None): return " AND ".join(self.sqls), tuple(self.params or ()) class Constraint(object): """ An object that can be passed to WhereNode.add() and knows how to pre-process itself prior to including in the WhereNode. """ def __init__(self, alias, col, field): self.alias, self.col, self.field = alias, col, field def __getstate__(self): """Save the state of the Constraint for pickling. Fields aren't necessarily pickleable, because they can have callable default values. So, instead of pickling the field store a reference so we can restore it manually """ obj_dict = self.__dict__.copy() if self.field: obj_dict['model'] = self.field.model obj_dict['field_name'] = self.field.name del obj_dict['field'] return obj_dict def __setstate__(self, data): """Restore the constraint """ model = data.pop('model', None) field_name = data.pop('field_name', None) self.__dict__.update(data) if model is not None: self.field = model._meta.get_field(field_name) else: self.field = None def prepare(self, lookup_type, value): if self.field: return self.field.get_prep_lookup(lookup_type, value) return value def process(self, lookup_type, value, connection): """ Returns a tuple of data suitable for inclusion in a WhereNode instance. """ # Because of circular imports, we need to import this here. from django.db.models.base import ObjectDoesNotExist try: if self.field: params = self.field.get_db_prep_lookup(lookup_type, value, connection=connection, prepared=True) db_type = self.field.db_type(connection=connection) else: # This branch is used at times when we add a comparison to NULL # (we don't really want to waste time looking up the associated # field object at the calling location). params = Field().get_db_prep_lookup(lookup_type, value, connection=connection, prepared=True) db_type = None except ObjectDoesNotExist: raise EmptyShortCircuit return (self.alias, self.col, db_type), params def relabel_aliases(self, change_map): if self.alias in change_map: self.alias = change_map[self.alias]