django1/django/db/models/sql/where.py

423 lines
16 KiB
Python

"""
Code to manage the creation and SQL rendering of 'where' constraints.
"""
import collections
import datetime
from itertools import repeat
from django.conf import settings
from django.db.models.fields import DateTimeField, Field
from django.db.models.sql.datastructures import EmptyResultSet, Empty
from django.db.models.sql.aggregates import Aggregate
from django.utils.six.moves import xrange
from django.utils import timezone
from django.utils import tree
# 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).
A child is usually a tuple of:
(Constraint(alias, targetcol, field), lookup_type, value)
where value can be either raw Python value, or Query, ExpressionNode or
something else knowing how to turn itself into SQL.
However, a child could also be any class with as_sql() and either
relabeled_clone() method or relabel_aliases() and clone() methods. The
second alternative should be used if the alias is not the only mutable
variable.
"""
default = AND
def _prepare_data(self, data):
"""
Prepare data for addition to the 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)):
return data
obj, lookup_type, value = data
if isinstance(value, collections.Iterator):
# Consume any generators immediately, so that we can determine
# emptiness and transform any non-empty values correctly.
value = list(value)
# The "value_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)
or (isinstance(obj.field, DateTimeField) and lookup_type != 'isnull')):
value_annotation = datetime.datetime
elif hasattr(value, 'value_annotation'):
value_annotation = value.value_annotation
else:
value_annotation = bool(value)
if hasattr(obj, "prepare"):
value = obj.prepare(lookup_type, value)
return (obj, lookup_type, value_annotation, value)
def as_sql(self, qn, connection):
"""
Returns the SQL version of the where clause and the value to be
substituted in. Returns '', [] if this node matches everything,
None, [] if this node is empty, and raises EmptyResultSet if this
node can't match anything.
"""
# Note that the logic here is made slightly more complex than
# necessary because there are two kind of empty nodes: Nodes
# containing 0 children, and nodes that are known to match everything.
# A match-everything node is different than empty node (which also
# technically matches everything) for backwards compatibility reasons.
# Refs #5261.
result = []
result_params = []
everything_childs, nothing_childs = 0, 0
non_empty_childs = len(self.children)
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:
nothing_childs += 1
else:
if sql:
result.append(sql)
result_params.extend(params)
else:
if sql is None:
# Skip empty childs totally.
non_empty_childs -= 1
continue
everything_childs += 1
# Check if this node matches nothing or everything.
# First check the amount of full nodes and empty nodes
# to make this node empty/full.
if self.connector == AND:
full_needed, empty_needed = non_empty_childs, 1
else:
full_needed, empty_needed = 1, non_empty_childs
# Now, check if this node is full/empty using the
# counts.
if empty_needed - nothing_childs <= 0:
if self.negated:
return '', []
else:
raise EmptyResultSet
if full_needed - everything_childs <= 0:
if self.negated:
raise EmptyResultSet
else:
return '', []
if non_empty_childs == 0:
# All the child nodes were empty, so this one is empty, too.
return None, []
conn = ' %s ' % self.connector
sql_string = conn.join(result)
if sql_string:
if self.negated:
# Some backends (Oracle at least) need parentheses
# around the inner SQL in the negated case, even if the
# inner SQL contains just a single expression.
sql_string = 'NOT (%s)' % sql_string
elif len(result) > 1:
sql_string = '(%s)' % sql_string
return sql_string, result_params
def get_cols(self):
cols = []
for child in self.children:
if hasattr(child, 'get_cols'):
cols.extend(child.get_cols())
else:
if isinstance(child[0], Constraint):
cols.append((child[0].alias, child[0].col))
if hasattr(child[3], 'get_cols'):
cols.extend(child[3].get_cols())
return cols
def make_atom(self, child, qn, connection):
"""
Turn a tuple (Constraint(table_alias, column_name, db_type),
lookup_type, value_annotation, params) into valid SQL.
The first item of the tuple may also be an Aggregate.
Returns the string for the SQL fragment and the parameters to use for
it.
"""
lvalue, lookup_type, value_annotation, params_or_value = child
field_internal_type = lvalue.field.get_internal_type() if lvalue.field else None
if isinstance(lvalue, Constraint):
try:
lvalue, params = lvalue.process(lookup_type, params_or_value, connection)
except EmptyShortCircuit:
raise EmptyResultSet
elif isinstance(lvalue, Aggregate):
params = lvalue.field.get_db_prep_lookup(lookup_type, params_or_value, connection)
else:
raise TypeError("'make_atom' expects a Constraint or an Aggregate "
"as the first item of its 'child' argument.")
if isinstance(lvalue, tuple):
# A direct database column lookup.
field_sql, field_params = self.sql_for_columns(lvalue, qn, connection, field_internal_type), []
else:
# A smart object with an as_sql() method.
field_sql, field_params = lvalue.as_sql(qn, connection)
is_datetime_field = value_annotation is datetime.datetime
cast_sql = connection.ops.datetime_cast_sql() if is_datetime_field else '%s'
if hasattr(params, 'as_sql'):
extra, params = params.as_sql(qn, connection)
cast_sql = ''
else:
extra = ''
params = field_params + params
if (len(params) == 1 and params[0] == '' and lookup_type == 'exact'
and connection.features.interprets_empty_strings_as_nulls):
lookup_type = 'isnull'
value_annotation = 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_annotation:
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 is_datetime_field and lookup_type in ('month', 'day', 'week_day',
'hour', 'minute', 'second'):
tzname = timezone.get_current_timezone_name() if settings.USE_TZ else None
sql, tz_params = connection.ops.datetime_extract_sql(lookup_type, field_sql, tzname)
return ('%s = %%s' % sql, tz_params + 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':
assert value_annotation in (True, False), "Invalid value_annotation for isnull"
return ('%s IS %sNULL' % (field_sql, ('' if value_annotation else 'NOT ')), ())
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, internal_type=None):
"""
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") and a list of parameters.
"""
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, internal_type) % lhs
def relabel_aliases(self, change_map):
"""
Relabels the alias values of any children. 'change_map' is a dictionary
mapping old (current) alias values to the new values.
"""
for pos, child in enumerate(self.children):
if hasattr(child, 'relabel_aliases'):
# For example another WhereNode
child.relabel_aliases(change_map)
elif isinstance(child, (list, tuple)):
# tuple starting with Constraint
child = (child[0].relabeled_clone(change_map),) + child[1:]
if hasattr(child[3], 'relabeled_clone'):
child = (child[0], child[1], child[2]) + (
child[3].relabeled_clone(change_map),)
self.children[pos] = child
def clone(self):
"""
Creates a clone of the tree. Must only be called on root nodes (nodes
with empty subtree_parents). Childs must be either (Contraint, lookup,
value) tuples, or objects supporting .clone().
"""
clone = self.__class__._new_instance(
children=[], connector=self.connector, negated=self.negated)
for child in self.children:
if hasattr(child, 'clone'):
clone.children.append(child.clone())
else:
clone.children.append(child)
return clone
class EmptyWhere(WhereNode):
def add(self, data, connector):
return
def as_sql(self, qn=None, connection=None):
raise EmptyResultSet
class EverythingNode(object):
"""
A node that matches everything.
"""
def as_sql(self, qn=None, connection=None):
return '', []
class NothingNode(object):
"""
A node that matches nothing.
"""
def as_sql(self, qn=None, connection=None):
raise EmptyResultSet
class ExtraWhere(object):
def __init__(self, sqls, params):
self.sqls = sqls
self.params = params
def as_sql(self, qn=None, connection=None):
sqls = ["(%s)" % sql for sql in self.sqls]
return " AND ".join(sqls), list(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 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 relabeled_clone(self, change_map):
if self.alias not in change_map:
return self
else:
new = Empty()
new.__class__ = self.__class__
new.alias, new.col, new.field = change_map[self.alias], self.col, self.field
return new
class SubqueryConstraint(object):
def __init__(self, alias, columns, targets, query_object):
self.alias = alias
self.columns = columns
self.targets = targets
self.query_object = query_object
def as_sql(self, qn, connection):
query = self.query_object
# QuerySet was sent
if hasattr(query, 'values'):
if query._db and connection.alias != query._db:
raise ValueError("Can't do subqueries with queries on different DBs.")
# Do not override already existing values.
if not hasattr(query, 'field_names'):
query = query.values(*self.targets)
else:
query = query._clone()
query = query.query
query.clear_ordering(True)
query_compiler = query.get_compiler(connection=connection)
return query_compiler.as_subquery_condition(self.alias, self.columns, qn)
def relabel_aliases(self, change_map):
self.alias = change_map.get(self.alias, self.alias)
def clone(self):
return self.__class__(
self.alias, self.columns, self.targets,
self.query_object)