import copy import datetime import inspect from decimal import Decimal from django.core.exceptions import EmptyResultSet, FieldError from django.db import connection from django.db.models import fields from django.db.models.constants import LOOKUP_SEP from django.db.models.query_utils import Q from django.db.utils import NotSupportedError from django.utils.deconstruct import deconstructible from django.utils.functional import cached_property from django.utils.hashable import make_hashable class SQLiteNumericMixin: """ Some expressions with output_field=DecimalField() must be cast to numeric to be properly filtered. """ def as_sqlite(self, compiler, connection, **extra_context): sql, params = self.as_sql(compiler, connection, **extra_context) try: if self.output_field.get_internal_type() == 'DecimalField': sql = 'CAST(%s AS NUMERIC)' % sql except FieldError: pass return sql, params class Combinable: """ Provide the ability to combine one or two objects with some connector. For example F('foo') + F('bar'). """ # Arithmetic connectors ADD = '+' SUB = '-' MUL = '*' DIV = '/' POW = '^' # The following is a quoted % operator - it is quoted because it can be # used in strings that also have parameter substitution. MOD = '%%' # Bitwise operators - note that these are generated by .bitand() # and .bitor(), the '&' and '|' are reserved for boolean operator # usage. BITAND = '&' BITOR = '|' BITLEFTSHIFT = '<<' BITRIGHTSHIFT = '>>' def _combine(self, other, connector, reversed): if not hasattr(other, 'resolve_expression'): # everything must be resolvable to an expression if isinstance(other, datetime.timedelta): other = DurationValue(other, output_field=fields.DurationField()) else: other = Value(other) if reversed: return CombinedExpression(other, connector, self) return CombinedExpression(self, connector, other) ############# # OPERATORS # ############# def __neg__(self): return self._combine(-1, self.MUL, False) def __add__(self, other): return self._combine(other, self.ADD, False) def __sub__(self, other): return self._combine(other, self.SUB, False) def __mul__(self, other): return self._combine(other, self.MUL, False) def __truediv__(self, other): return self._combine(other, self.DIV, False) def __mod__(self, other): return self._combine(other, self.MOD, False) def __pow__(self, other): return self._combine(other, self.POW, False) def __and__(self, other): if getattr(self, 'conditional', False) and getattr(other, 'conditional', False): return Q(self) & Q(other) raise NotImplementedError( "Use .bitand() and .bitor() for bitwise logical operations." ) def bitand(self, other): return self._combine(other, self.BITAND, False) def bitleftshift(self, other): return self._combine(other, self.BITLEFTSHIFT, False) def bitrightshift(self, other): return self._combine(other, self.BITRIGHTSHIFT, False) def __or__(self, other): if getattr(self, 'conditional', False) and getattr(other, 'conditional', False): return Q(self) | Q(other) raise NotImplementedError( "Use .bitand() and .bitor() for bitwise logical operations." ) def bitor(self, other): return self._combine(other, self.BITOR, False) def __radd__(self, other): return self._combine(other, self.ADD, True) def __rsub__(self, other): return self._combine(other, self.SUB, True) def __rmul__(self, other): return self._combine(other, self.MUL, True) def __rtruediv__(self, other): return self._combine(other, self.DIV, True) def __rmod__(self, other): return self._combine(other, self.MOD, True) def __rpow__(self, other): return self._combine(other, self.POW, True) def __rand__(self, other): raise NotImplementedError( "Use .bitand() and .bitor() for bitwise logical operations." ) def __ror__(self, other): raise NotImplementedError( "Use .bitand() and .bitor() for bitwise logical operations." ) @deconstructible class BaseExpression: """Base class for all query expressions.""" # aggregate specific fields is_summary = False _output_field_resolved_to_none = False # Can the expression be used in a WHERE clause? filterable = True # Can the expression can be used as a source expression in Window? window_compatible = False def __init__(self, output_field=None): if output_field is not None: self.output_field = output_field def __getstate__(self): state = self.__dict__.copy() state.pop('convert_value', None) return state def get_db_converters(self, connection): return ( [] if self.convert_value is self._convert_value_noop else [self.convert_value] ) + self.output_field.get_db_converters(connection) def get_source_expressions(self): return [] def set_source_expressions(self, exprs): assert not exprs def _parse_expressions(self, *expressions): return [ arg if hasattr(arg, 'resolve_expression') else ( F(arg) if isinstance(arg, str) else Value(arg) ) for arg in expressions ] def as_sql(self, compiler, connection): """ Responsible for returning a (sql, [params]) tuple to be included in the current query. Different backends can provide their own implementation, by providing an `as_{vendor}` method and patching the Expression: ``` def override_as_sql(self, compiler, connection): # custom logic return super().as_sql(compiler, connection) setattr(Expression, 'as_' + connection.vendor, override_as_sql) ``` Arguments: * compiler: the query compiler responsible for generating the query. Must have a compile method, returning a (sql, [params]) tuple. Calling compiler(value) will return a quoted `value`. * connection: the database connection used for the current query. Return: (sql, params) Where `sql` is a string containing ordered sql parameters to be replaced with the elements of the list `params`. """ raise NotImplementedError("Subclasses must implement as_sql()") @cached_property def contains_aggregate(self): return any(expr and expr.contains_aggregate for expr in self.get_source_expressions()) @cached_property def contains_over_clause(self): return any(expr and expr.contains_over_clause for expr in self.get_source_expressions()) @cached_property def contains_column_references(self): return any(expr and expr.contains_column_references for expr in self.get_source_expressions()) def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False): """ Provide the chance to do any preprocessing or validation before being added to the query. Arguments: * query: the backend query implementation * allow_joins: boolean allowing or denying use of joins in this query * reuse: a set of reusable joins for multijoins * summarize: a terminal aggregate clause * for_save: whether this expression about to be used in a save or update Return: an Expression to be added to the query. """ c = self.copy() c.is_summary = summarize c.set_source_expressions([ expr.resolve_expression(query, allow_joins, reuse, summarize) if expr else None for expr in c.get_source_expressions() ]) return c @property def conditional(self): return isinstance(self.output_field, fields.BooleanField) @property def field(self): return self.output_field @cached_property def output_field(self): """Return the output type of this expressions.""" output_field = self._resolve_output_field() if output_field is None: self._output_field_resolved_to_none = True raise FieldError('Cannot resolve expression type, unknown output_field') return output_field @cached_property def _output_field_or_none(self): """ Return the output field of this expression, or None if _resolve_output_field() didn't return an output type. """ try: return self.output_field except FieldError: if not self._output_field_resolved_to_none: raise def _resolve_output_field(self): """ Attempt to infer the output type of the expression. If the output fields of all source fields match then, simply infer the same type here. This isn't always correct, but it makes sense most of the time. Consider the difference between `2 + 2` and `2 / 3`. Inferring the type here is a convenience for the common case. The user should supply their own output_field with more complex computations. If a source's output field resolves to None, exclude it from this check. If all sources are None, then an error is raised higher up the stack in the output_field property. """ sources_iter = (source for source in self.get_source_fields() if source is not None) for output_field in sources_iter: for source in sources_iter: if not isinstance(output_field, source.__class__): raise FieldError( 'Expression contains mixed types: %s, %s. You must ' 'set output_field.' % ( output_field.__class__.__name__, source.__class__.__name__, ) ) return output_field @staticmethod def _convert_value_noop(value, expression, connection): return value @cached_property def convert_value(self): """ Expressions provide their own converters because users have the option of manually specifying the output_field which may be a different type from the one the database returns. """ field = self.output_field internal_type = field.get_internal_type() if internal_type == 'FloatField': return lambda value, expression, connection: None if value is None else float(value) elif internal_type.endswith('IntegerField'): return lambda value, expression, connection: None if value is None else int(value) elif internal_type == 'DecimalField': return lambda value, expression, connection: None if value is None else Decimal(value) return self._convert_value_noop def get_lookup(self, lookup): return self.output_field.get_lookup(lookup) def get_transform(self, name): return self.output_field.get_transform(name) def relabeled_clone(self, change_map): clone = self.copy() clone.set_source_expressions([ e.relabeled_clone(change_map) if e is not None else None for e in self.get_source_expressions() ]) return clone def copy(self): return copy.copy(self) def get_group_by_cols(self, alias=None): if not self.contains_aggregate: return [self] cols = [] for source in self.get_source_expressions(): cols.extend(source.get_group_by_cols()) return cols def get_source_fields(self): """Return the underlying field types used by this aggregate.""" return [e._output_field_or_none for e in self.get_source_expressions()] def asc(self, **kwargs): return OrderBy(self, **kwargs) def desc(self, **kwargs): return OrderBy(self, descending=True, **kwargs) def reverse_ordering(self): return self def flatten(self): """ Recursively yield this expression and all subexpressions, in depth-first order. """ yield self for expr in self.get_source_expressions(): if expr: yield from expr.flatten() def select_format(self, compiler, sql, params): """ Custom format for select clauses. For example, EXISTS expressions need to be wrapped in CASE WHEN on Oracle. """ return self.output_field.select_format(compiler, sql, params) @cached_property def identity(self): constructor_signature = inspect.signature(self.__init__) args, kwargs = self._constructor_args signature = constructor_signature.bind_partial(*args, **kwargs) signature.apply_defaults() arguments = signature.arguments.items() identity = [self.__class__] for arg, value in arguments: if isinstance(value, fields.Field): if value.name and value.model: value = (value.model._meta.label, value.name) else: value = type(value) else: value = make_hashable(value) identity.append((arg, value)) return tuple(identity) def __eq__(self, other): return isinstance(other, BaseExpression) and other.identity == self.identity def __hash__(self): return hash(self.identity) class Expression(BaseExpression, Combinable): """An expression that can be combined with other expressions.""" pass class CombinedExpression(SQLiteNumericMixin, Expression): def __init__(self, lhs, connector, rhs, output_field=None): super().__init__(output_field=output_field) self.connector = connector self.lhs = lhs self.rhs = rhs def __repr__(self): return "<{}: {}>".format(self.__class__.__name__, self) def __str__(self): return "{} {} {}".format(self.lhs, self.connector, self.rhs) def get_source_expressions(self): return [self.lhs, self.rhs] def set_source_expressions(self, exprs): self.lhs, self.rhs = exprs def as_sql(self, compiler, connection): try: lhs_output = self.lhs.output_field except FieldError: lhs_output = None try: rhs_output = self.rhs.output_field except FieldError: rhs_output = None if (not connection.features.has_native_duration_field and ((lhs_output and lhs_output.get_internal_type() == 'DurationField') or (rhs_output and rhs_output.get_internal_type() == 'DurationField'))): return DurationExpression(self.lhs, self.connector, self.rhs).as_sql(compiler, connection) if (lhs_output and rhs_output and self.connector == self.SUB and lhs_output.get_internal_type() in {'DateField', 'DateTimeField', 'TimeField'} and lhs_output.get_internal_type() == rhs_output.get_internal_type()): return TemporalSubtraction(self.lhs, self.rhs).as_sql(compiler, connection) expressions = [] expression_params = [] sql, params = compiler.compile(self.lhs) expressions.append(sql) expression_params.extend(params) sql, params = compiler.compile(self.rhs) expressions.append(sql) expression_params.extend(params) # order of precedence expression_wrapper = '(%s)' sql = connection.ops.combine_expression(self.connector, expressions) return expression_wrapper % sql, expression_params def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False): c = self.copy() c.is_summary = summarize c.lhs = c.lhs.resolve_expression(query, allow_joins, reuse, summarize, for_save) c.rhs = c.rhs.resolve_expression(query, allow_joins, reuse, summarize, for_save) return c class DurationExpression(CombinedExpression): def compile(self, side, compiler, connection): if not isinstance(side, DurationValue): try: output = side.output_field except FieldError: pass else: if output.get_internal_type() == 'DurationField': sql, params = compiler.compile(side) return connection.ops.format_for_duration_arithmetic(sql), params return compiler.compile(side) def as_sql(self, compiler, connection): connection.ops.check_expression_support(self) expressions = [] expression_params = [] sql, params = self.compile(self.lhs, compiler, connection) expressions.append(sql) expression_params.extend(params) sql, params = self.compile(self.rhs, compiler, connection) expressions.append(sql) expression_params.extend(params) # order of precedence expression_wrapper = '(%s)' sql = connection.ops.combine_duration_expression(self.connector, expressions) return expression_wrapper % sql, expression_params class TemporalSubtraction(CombinedExpression): output_field = fields.DurationField() def __init__(self, lhs, rhs): super().__init__(lhs, self.SUB, rhs) def as_sql(self, compiler, connection): connection.ops.check_expression_support(self) lhs = compiler.compile(self.lhs) rhs = compiler.compile(self.rhs) return connection.ops.subtract_temporals(self.lhs.output_field.get_internal_type(), lhs, rhs) @deconstructible class F(Combinable): """An object capable of resolving references to existing query objects.""" def __init__(self, name): """ Arguments: * name: the name of the field this expression references """ self.name = name def __repr__(self): return "{}({})".format(self.__class__.__name__, self.name) def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False, simple_col=False): return query.resolve_ref(self.name, allow_joins, reuse, summarize, simple_col) def asc(self, **kwargs): return OrderBy(self, **kwargs) def desc(self, **kwargs): return OrderBy(self, descending=True, **kwargs) def __eq__(self, other): return self.__class__ == other.__class__ and self.name == other.name def __hash__(self): return hash(self.name) class ResolvedOuterRef(F): """ An object that contains a reference to an outer query. In this case, the reference to the outer query has been resolved because the inner query has been used as a subquery. """ contains_aggregate = False def as_sql(self, *args, **kwargs): raise ValueError( 'This queryset contains a reference to an outer query and may ' 'only be used in a subquery.' ) def resolve_expression(self, *args, **kwargs): col = super().resolve_expression(*args, **kwargs) # FIXME: Rename possibly_multivalued to multivalued and fix detection # for non-multivalued JOINs (e.g. foreign key fields). This should take # into account only many-to-many and one-to-many relationships. col.possibly_multivalued = LOOKUP_SEP in self.name return col def relabeled_clone(self, relabels): return self class OuterRef(F): def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False, simple_col=False): if isinstance(self.name, self.__class__): return self.name return ResolvedOuterRef(self.name) class Func(SQLiteNumericMixin, Expression): """An SQL function call.""" function = None template = '%(function)s(%(expressions)s)' arg_joiner = ', ' arity = None # The number of arguments the function accepts. def __init__(self, *expressions, output_field=None, **extra): if self.arity is not None and len(expressions) != self.arity: raise TypeError( "'%s' takes exactly %s %s (%s given)" % ( self.__class__.__name__, self.arity, "argument" if self.arity == 1 else "arguments", len(expressions), ) ) super().__init__(output_field=output_field) self.source_expressions = self._parse_expressions(*expressions) self.extra = extra def __repr__(self): args = self.arg_joiner.join(str(arg) for arg in self.source_expressions) extra = {**self.extra, **self._get_repr_options()} if extra: extra = ', '.join(str(key) + '=' + str(val) for key, val in sorted(extra.items())) return "{}({}, {})".format(self.__class__.__name__, args, extra) return "{}({})".format(self.__class__.__name__, args) def _get_repr_options(self): """Return a dict of extra __init__() options to include in the repr.""" return {} def get_source_expressions(self): return self.source_expressions def set_source_expressions(self, exprs): self.source_expressions = exprs def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False): c = self.copy() c.is_summary = summarize for pos, arg in enumerate(c.source_expressions): c.source_expressions[pos] = arg.resolve_expression(query, allow_joins, reuse, summarize, for_save) return c def as_sql(self, compiler, connection, function=None, template=None, arg_joiner=None, **extra_context): connection.ops.check_expression_support(self) sql_parts = [] params = [] for arg in self.source_expressions: arg_sql, arg_params = compiler.compile(arg) sql_parts.append(arg_sql) params.extend(arg_params) data = {**self.extra, **extra_context} # Use the first supplied value in this order: the parameter to this # method, a value supplied in __init__()'s **extra (the value in # `data`), or the value defined on the class. if function is not None: data['function'] = function else: data.setdefault('function', self.function) template = template or data.get('template', self.template) arg_joiner = arg_joiner or data.get('arg_joiner', self.arg_joiner) data['expressions'] = data['field'] = arg_joiner.join(sql_parts) return template % data, params def copy(self): copy = super().copy() copy.source_expressions = self.source_expressions[:] copy.extra = self.extra.copy() return copy class Value(Expression): """Represent a wrapped value as a node within an expression.""" def __init__(self, value, output_field=None): """ Arguments: * value: the value this expression represents. The value will be added into the sql parameter list and properly quoted. * output_field: an instance of the model field type that this expression will return, such as IntegerField() or CharField(). """ super().__init__(output_field=output_field) self.value = value def __repr__(self): return "{}({})".format(self.__class__.__name__, self.value) def as_sql(self, compiler, connection): connection.ops.check_expression_support(self) val = self.value output_field = self._output_field_or_none if output_field is not None: if self.for_save: val = output_field.get_db_prep_save(val, connection=connection) else: val = output_field.get_db_prep_value(val, connection=connection) if hasattr(output_field, 'get_placeholder'): return output_field.get_placeholder(val, compiler, connection), [val] if val is None: # cx_Oracle does not always convert None to the appropriate # NULL type (like in case expressions using numbers), so we # use a literal SQL NULL return 'NULL', [] return '%s', [val] def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False): c = super().resolve_expression(query, allow_joins, reuse, summarize, for_save) c.for_save = for_save return c def get_group_by_cols(self, alias=None): return [] class DurationValue(Value): def as_sql(self, compiler, connection): connection.ops.check_expression_support(self) if connection.features.has_native_duration_field: return super().as_sql(compiler, connection) return connection.ops.date_interval_sql(self.value), [] class RawSQL(Expression): def __init__(self, sql, params, output_field=None): if output_field is None: output_field = fields.Field() self.sql, self.params = sql, params super().__init__(output_field=output_field) def __repr__(self): return "{}({}, {})".format(self.__class__.__name__, self.sql, self.params) def as_sql(self, compiler, connection): return '(%s)' % self.sql, self.params def get_group_by_cols(self, alias=None): return [self] def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False): # Resolve parents fields used in raw SQL. for parent in query.model._meta.get_parent_list(): for parent_field in parent._meta.local_fields: _, column_name = parent_field.get_attname_column() if column_name.lower() in self.sql.lower(): query.resolve_ref(parent_field.name, allow_joins, reuse, summarize) break return super().resolve_expression(query, allow_joins, reuse, summarize, for_save) class Star(Expression): def __repr__(self): return "'*'" def as_sql(self, compiler, connection): return '*', [] class Random(Expression): output_field = fields.FloatField() def __repr__(self): return "Random()" def as_sql(self, compiler, connection): return connection.ops.random_function_sql(), [] class Col(Expression): contains_column_references = True possibly_multivalued = False def __init__(self, alias, target, output_field=None): if output_field is None: output_field = target super().__init__(output_field=output_field) self.alias, self.target = alias, target def __repr__(self): return "{}({}, {})".format( self.__class__.__name__, self.alias, self.target) def as_sql(self, compiler, connection): qn = compiler.quote_name_unless_alias return "%s.%s" % (qn(self.alias), qn(self.target.column)), [] def relabeled_clone(self, relabels): return self.__class__(relabels.get(self.alias, self.alias), self.target, self.output_field) def get_group_by_cols(self, alias=None): return [self] def get_db_converters(self, connection): if self.target == self.output_field: return self.output_field.get_db_converters(connection) return (self.output_field.get_db_converters(connection) + self.target.get_db_converters(connection)) class SimpleCol(Expression): """ Represents the SQL of a column name without the table name. This variant of Col doesn't include the table name (or an alias) to avoid a syntax error in check constraints. """ contains_column_references = True def __init__(self, target, output_field=None): if output_field is None: output_field = target super().__init__(output_field=output_field) self.target = target def __repr__(self): return '{}({})'.format(self.__class__.__name__, self.target) def as_sql(self, compiler, connection): qn = compiler.quote_name_unless_alias return qn(self.target.column), [] def get_group_by_cols(self, alias=None): return [self] def get_db_converters(self, connection): if self.target == self.output_field: return self.output_field.get_db_converters(connection) return ( self.output_field.get_db_converters(connection) + self.target.get_db_converters(connection) ) class Ref(Expression): """ Reference to column alias of the query. For example, Ref('sum_cost') in qs.annotate(sum_cost=Sum('cost')) query. """ def __init__(self, refs, source): super().__init__() self.refs, self.source = refs, source def __repr__(self): return "{}({}, {})".format(self.__class__.__name__, self.refs, self.source) def get_source_expressions(self): return [self.source] def set_source_expressions(self, exprs): self.source, = exprs def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False): # The sub-expression `source` has already been resolved, as this is # just a reference to the name of `source`. return self def relabeled_clone(self, relabels): return self def as_sql(self, compiler, connection): return connection.ops.quote_name(self.refs), [] def get_group_by_cols(self, alias=None): return [self] class ExpressionList(Func): """ An expression containing multiple expressions. Can be used to provide a list of expressions as an argument to another expression, like an ordering clause. """ template = '%(expressions)s' def __init__(self, *expressions, **extra): if not expressions: raise ValueError('%s requires at least one expression.' % self.__class__.__name__) super().__init__(*expressions, **extra) def __str__(self): return self.arg_joiner.join(str(arg) for arg in self.source_expressions) class ExpressionWrapper(Expression): """ An expression that can wrap another expression so that it can provide extra context to the inner expression, such as the output_field. """ def __init__(self, expression, output_field): super().__init__(output_field=output_field) self.expression = expression def set_source_expressions(self, exprs): self.expression = exprs[0] def get_source_expressions(self): return [self.expression] def as_sql(self, compiler, connection): return self.expression.as_sql(compiler, connection) def __repr__(self): return "{}({})".format(self.__class__.__name__, self.expression) class When(Expression): template = 'WHEN %(condition)s THEN %(result)s' # This isn't a complete conditional expression, must be used in Case(). conditional = False def __init__(self, condition=None, then=None, **lookups): if lookups and condition is None: condition, lookups = Q(**lookups), None if condition is None or not getattr(condition, 'conditional', False) or lookups: raise TypeError( 'When() supports a Q object, a boolean expression, or lookups ' 'as a condition.' ) if isinstance(condition, Q) and not condition: raise ValueError("An empty Q() can't be used as a When() condition.") super().__init__(output_field=None) self.condition = condition self.result = self._parse_expressions(then)[0] def __str__(self): return "WHEN %r THEN %r" % (self.condition, self.result) def __repr__(self): return "<%s: %s>" % (self.__class__.__name__, self) def get_source_expressions(self): return [self.condition, self.result] def set_source_expressions(self, exprs): self.condition, self.result = exprs def get_source_fields(self): # We're only interested in the fields of the result expressions. return [self.result._output_field_or_none] def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False): c = self.copy() c.is_summary = summarize if hasattr(c.condition, 'resolve_expression'): c.condition = c.condition.resolve_expression(query, allow_joins, reuse, summarize, False) c.result = c.result.resolve_expression(query, allow_joins, reuse, summarize, for_save) return c def as_sql(self, compiler, connection, template=None, **extra_context): connection.ops.check_expression_support(self) template_params = extra_context sql_params = [] condition_sql, condition_params = compiler.compile(self.condition) template_params['condition'] = condition_sql sql_params.extend(condition_params) result_sql, result_params = compiler.compile(self.result) template_params['result'] = result_sql sql_params.extend(result_params) template = template or self.template return template % template_params, sql_params def get_group_by_cols(self, alias=None): # This is not a complete expression and cannot be used in GROUP BY. cols = [] for source in self.get_source_expressions(): cols.extend(source.get_group_by_cols()) return cols class Case(Expression): """ An SQL searched CASE expression: CASE WHEN n > 0 THEN 'positive' WHEN n < 0 THEN 'negative' ELSE 'zero' END """ template = 'CASE %(cases)s ELSE %(default)s END' case_joiner = ' ' def __init__(self, *cases, default=None, output_field=None, **extra): if not all(isinstance(case, When) for case in cases): raise TypeError("Positional arguments must all be When objects.") super().__init__(output_field) self.cases = list(cases) self.default = self._parse_expressions(default)[0] self.extra = extra def __str__(self): return "CASE %s, ELSE %r" % (', '.join(str(c) for c in self.cases), self.default) def __repr__(self): return "<%s: %s>" % (self.__class__.__name__, self) def get_source_expressions(self): return self.cases + [self.default] def set_source_expressions(self, exprs): *self.cases, self.default = exprs def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False): c = self.copy() c.is_summary = summarize for pos, case in enumerate(c.cases): c.cases[pos] = case.resolve_expression(query, allow_joins, reuse, summarize, for_save) c.default = c.default.resolve_expression(query, allow_joins, reuse, summarize, for_save) return c def copy(self): c = super().copy() c.cases = c.cases[:] return c def as_sql(self, compiler, connection, template=None, case_joiner=None, **extra_context): connection.ops.check_expression_support(self) if not self.cases: return compiler.compile(self.default) template_params = {**self.extra, **extra_context} case_parts = [] sql_params = [] for case in self.cases: try: case_sql, case_params = compiler.compile(case) except EmptyResultSet: continue case_parts.append(case_sql) sql_params.extend(case_params) default_sql, default_params = compiler.compile(self.default) if not case_parts: return default_sql, default_params case_joiner = case_joiner or self.case_joiner template_params['cases'] = case_joiner.join(case_parts) template_params['default'] = default_sql sql_params.extend(default_params) template = template or template_params.get('template', self.template) sql = template % template_params if self._output_field_or_none is not None: sql = connection.ops.unification_cast_sql(self.output_field) % sql return sql, sql_params class Subquery(Expression): """ An explicit subquery. It may contain OuterRef() references to the outer query which will be resolved when it is applied to that query. """ template = '(%(subquery)s)' contains_aggregate = False def __init__(self, queryset, output_field=None, **extra): self.query = queryset.query self.extra = extra # Prevent the QuerySet from being evaluated. self.queryset = queryset._chain(_result_cache=[], prefetch_done=True) super().__init__(output_field) def __getstate__(self): state = super().__getstate__() args, kwargs = state['_constructor_args'] if args: args = (self.queryset, *args[1:]) else: kwargs['queryset'] = self.queryset state['_constructor_args'] = args, kwargs return state def get_source_expressions(self): return [self.query] def set_source_expressions(self, exprs): self.query = exprs[0] def _resolve_output_field(self): return self.query.output_field def copy(self): clone = super().copy() clone.query = clone.query.clone() return clone @property def external_aliases(self): return self.query.external_aliases def as_sql(self, compiler, connection, template=None, **extra_context): connection.ops.check_expression_support(self) template_params = {**self.extra, **extra_context} subquery_sql, sql_params = self.query.as_sql(compiler, connection) template_params['subquery'] = subquery_sql[1:-1] template = template or template_params.get('template', self.template) sql = template % template_params return sql, sql_params def get_group_by_cols(self, alias=None): if alias: return [Ref(alias, self)] external_cols = self.query.get_external_cols() if any(col.possibly_multivalued for col in external_cols): return [self] return external_cols class Exists(Subquery): template = 'EXISTS(%(subquery)s)' output_field = fields.BooleanField() def __init__(self, queryset, negated=False, **kwargs): # As a performance optimization, remove ordering since EXISTS doesn't # care about it, just whether or not a row matches. queryset = queryset.order_by() self.negated = negated super().__init__(queryset, **kwargs) def __invert__(self): clone = self.copy() clone.negated = not self.negated return clone def as_sql(self, compiler, connection, template=None, **extra_context): sql, params = super().as_sql(compiler, connection, template, **extra_context) if self.negated: sql = 'NOT {}'.format(sql) return sql, params def select_format(self, compiler, sql, params): # Wrap EXISTS() with a CASE WHEN expression if a database backend # (e.g. Oracle) doesn't support boolean expression in SELECT or GROUP # BY list. if not compiler.connection.features.supports_boolean_expr_in_select_clause: sql = 'CASE WHEN {} THEN 1 ELSE 0 END'.format(sql) return sql, params class OrderBy(BaseExpression): template = '%(expression)s %(ordering)s' conditional = False def __init__(self, expression, descending=False, nulls_first=False, nulls_last=False): if nulls_first and nulls_last: raise ValueError('nulls_first and nulls_last are mutually exclusive') self.nulls_first = nulls_first self.nulls_last = nulls_last self.descending = descending if not hasattr(expression, 'resolve_expression'): raise ValueError('expression must be an expression type') self.expression = expression def __repr__(self): return "{}({}, descending={})".format( self.__class__.__name__, self.expression, self.descending) def set_source_expressions(self, exprs): self.expression = exprs[0] def get_source_expressions(self): return [self.expression] def as_sql(self, compiler, connection, template=None, **extra_context): if not template: if self.nulls_last: template = '%s NULLS LAST' % self.template elif self.nulls_first: template = '%s NULLS FIRST' % self.template connection.ops.check_expression_support(self) expression_sql, params = compiler.compile(self.expression) placeholders = { 'expression': expression_sql, 'ordering': 'DESC' if self.descending else 'ASC', **extra_context, } template = template or self.template params *= template.count('%(expression)s') return (template % placeholders).rstrip(), params def as_sqlite(self, compiler, connection): template = None if self.nulls_last: template = '%(expression)s IS NULL, %(expression)s %(ordering)s' elif self.nulls_first: template = '%(expression)s IS NOT NULL, %(expression)s %(ordering)s' return self.as_sql(compiler, connection, template=template) def as_mysql(self, compiler, connection): template = None if self.nulls_last: template = 'IF(ISNULL(%(expression)s),1,0), %(expression)s %(ordering)s ' elif self.nulls_first: template = 'IF(ISNULL(%(expression)s),0,1), %(expression)s %(ordering)s ' return self.as_sql(compiler, connection, template=template) def as_oracle(self, compiler, connection): # Oracle doesn't allow ORDER BY EXISTS() unless it's wrapped in # a CASE WHEN. if isinstance(self.expression, Exists): copy = self.copy() copy.expression = Case( When(self.expression, then=True), default=False, output_field=fields.BooleanField(), ) return copy.as_sql(compiler, connection) return self.as_sql(compiler, connection) def get_group_by_cols(self, alias=None): cols = [] for source in self.get_source_expressions(): cols.extend(source.get_group_by_cols()) return cols def reverse_ordering(self): self.descending = not self.descending if self.nulls_first or self.nulls_last: self.nulls_first = not self.nulls_first self.nulls_last = not self.nulls_last return self def asc(self): self.descending = False def desc(self): self.descending = True class Window(Expression): template = '%(expression)s OVER (%(window)s)' # Although the main expression may either be an aggregate or an # expression with an aggregate function, the GROUP BY that will # be introduced in the query as a result is not desired. contains_aggregate = False contains_over_clause = True filterable = False def __init__(self, expression, partition_by=None, order_by=None, frame=None, output_field=None): self.partition_by = partition_by self.order_by = order_by self.frame = frame if not getattr(expression, 'window_compatible', False): raise ValueError( "Expression '%s' isn't compatible with OVER clauses." % expression.__class__.__name__ ) if self.partition_by is not None: if not isinstance(self.partition_by, (tuple, list)): self.partition_by = (self.partition_by,) self.partition_by = ExpressionList(*self.partition_by) if self.order_by is not None: if isinstance(self.order_by, (list, tuple)): self.order_by = ExpressionList(*self.order_by) elif not isinstance(self.order_by, BaseExpression): raise ValueError( 'order_by must be either an Expression or a sequence of ' 'expressions.' ) super().__init__(output_field=output_field) self.source_expression = self._parse_expressions(expression)[0] def _resolve_output_field(self): return self.source_expression.output_field def get_source_expressions(self): return [self.source_expression, self.partition_by, self.order_by, self.frame] def set_source_expressions(self, exprs): self.source_expression, self.partition_by, self.order_by, self.frame = exprs def as_sql(self, compiler, connection, template=None): connection.ops.check_expression_support(self) if not connection.features.supports_over_clause: raise NotSupportedError('This backend does not support window expressions.') expr_sql, params = compiler.compile(self.source_expression) window_sql, window_params = [], [] if self.partition_by is not None: sql_expr, sql_params = self.partition_by.as_sql( compiler=compiler, connection=connection, template='PARTITION BY %(expressions)s', ) window_sql.extend(sql_expr) window_params.extend(sql_params) if self.order_by is not None: window_sql.append(' ORDER BY ') order_sql, order_params = compiler.compile(self.order_by) window_sql.extend(order_sql) window_params.extend(order_params) if self.frame: frame_sql, frame_params = compiler.compile(self.frame) window_sql.append(' ' + frame_sql) window_params.extend(frame_params) params.extend(window_params) template = template or self.template return template % { 'expression': expr_sql, 'window': ''.join(window_sql).strip() }, params def __str__(self): return '{} OVER ({}{}{})'.format( str(self.source_expression), 'PARTITION BY ' + str(self.partition_by) if self.partition_by else '', 'ORDER BY ' + str(self.order_by) if self.order_by else '', str(self.frame or ''), ) def __repr__(self): return '<%s: %s>' % (self.__class__.__name__, self) def get_group_by_cols(self, alias=None): return [] class WindowFrame(Expression): """ Model the frame clause in window expressions. There are two types of frame clauses which are subclasses, however, all processing and validation (by no means intended to be complete) is done here. Thus, providing an end for a frame is optional (the default is UNBOUNDED FOLLOWING, which is the last row in the frame). """ template = '%(frame_type)s BETWEEN %(start)s AND %(end)s' def __init__(self, start=None, end=None): self.start = Value(start) self.end = Value(end) def set_source_expressions(self, exprs): self.start, self.end = exprs def get_source_expressions(self): return [self.start, self.end] def as_sql(self, compiler, connection): connection.ops.check_expression_support(self) start, end = self.window_frame_start_end(connection, self.start.value, self.end.value) return self.template % { 'frame_type': self.frame_type, 'start': start, 'end': end, }, [] def __repr__(self): return '<%s: %s>' % (self.__class__.__name__, self) def get_group_by_cols(self, alias=None): return [] def __str__(self): if self.start.value is not None and self.start.value < 0: start = '%d %s' % (abs(self.start.value), connection.ops.PRECEDING) elif self.start.value is not None and self.start.value == 0: start = connection.ops.CURRENT_ROW else: start = connection.ops.UNBOUNDED_PRECEDING if self.end.value is not None and self.end.value > 0: end = '%d %s' % (self.end.value, connection.ops.FOLLOWING) elif self.end.value is not None and self.end.value == 0: end = connection.ops.CURRENT_ROW else: end = connection.ops.UNBOUNDED_FOLLOWING return self.template % { 'frame_type': self.frame_type, 'start': start, 'end': end, } def window_frame_start_end(self, connection, start, end): raise NotImplementedError('Subclasses must implement window_frame_start_end().') class RowRange(WindowFrame): frame_type = 'ROWS' def window_frame_start_end(self, connection, start, end): return connection.ops.window_frame_rows_start_end(start, end) class ValueRange(WindowFrame): frame_type = 'RANGE' def window_frame_start_end(self, connection, start, end): return connection.ops.window_frame_range_start_end(start, end)