"""
Code to manage the creation and SQL rendering of 'where' constraints.
"""
import datetime
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 (alias, col_name, field_obj, lookup_type,
value), which is then slightly munged before being stored (to avoid
storing any reference to field objects). Otherwise, the 'data' is
stored unchanged and can be anything 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)
return ('%s IN (%s)' % (field_sql, ', '.join(['%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]
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