diff options
Diffstat (limited to 'lib/sqlalchemy/sql/elements.py')
| -rw-r--r-- | lib/sqlalchemy/sql/elements.py | 450 |
1 files changed, 370 insertions, 80 deletions
diff --git a/lib/sqlalchemy/sql/elements.py b/lib/sqlalchemy/sql/elements.py index 27ecce2b0..70046c66b 100644 --- a/lib/sqlalchemy/sql/elements.py +++ b/lib/sqlalchemy/sql/elements.py @@ -124,67 +124,6 @@ def literal(value, type_=None): return BindParameter(None, value, type_=type_, unique=True) -def type_coerce(expression, type_): - """Associate a SQL expression with a particular type, without rendering - ``CAST``. - - E.g.:: - - from sqlalchemy import type_coerce - - stmt = select([type_coerce(log_table.date_string, StringDateTime())]) - - The above construct will produce SQL that is usually otherwise unaffected - by the :func:`.type_coerce` call:: - - SELECT date_string FROM log - - However, when result rows are fetched, the ``StringDateTime`` type - will be applied to result rows on behalf of the ``date_string`` column. - - A type that features bound-value handling will also have that behavior - take effect when literal values or :func:`.bindparam` constructs are - passed to :func:`.type_coerce` as targets. - For example, if a type implements the :meth:`.TypeEngine.bind_expression` - method or :meth:`.TypeEngine.bind_processor` method or equivalent, - these functions will take effect at statement compilation/execution time - when a literal value is passed, as in:: - - # bound-value handling of MyStringType will be applied to the - # literal value "some string" - stmt = select([type_coerce("some string", MyStringType)]) - - :func:`.type_coerce` is similar to the :func:`.cast` function, - except that it does not render the ``CAST`` expression in the resulting - statement. - - :param expression: A SQL expression, such as a :class:`.ColumnElement` - expression or a Python string which will be coerced into a bound literal - value. - - :param type_: A :class:`.TypeEngine` class or instance indicating - the type to which the expression is coerced. - - .. seealso:: - - :func:`.cast` - - """ - type_ = type_api.to_instance(type_) - - if hasattr(expression, '__clause_element__'): - return type_coerce(expression.__clause_element__(), type_) - elif isinstance(expression, BindParameter): - bp = expression._clone() - bp.type = type_ - return bp - elif not isinstance(expression, Visitable): - if expression is None: - return Null() - else: - return literal(expression, type_=type_) - else: - return Label(None, expression, type_=type_) def outparam(key, type_=None): @@ -700,6 +639,8 @@ class ColumnElement(operators.ColumnOperators, ClauseElement): self.type._type_affinity is type_api.BOOLEANTYPE._type_affinity): return AsBoolean(self, operators.istrue, operators.isfalse) + elif (against in (operators.any_op, operators.all_op)): + return Grouping(self) else: return self @@ -715,7 +656,14 @@ class ColumnElement(operators.ColumnOperators, ClauseElement): @util.memoized_property def comparator(self): - return self.type.comparator_factory(self) + try: + comparator_factory = self.type.comparator_factory + except AttributeError: + raise TypeError( + "Object %r associated with '.type' attribute " + "is not a TypeEngine class or object" % self.type) + else: + return comparator_factory(self) def __getattr__(self, key): try: @@ -837,6 +785,16 @@ class ColumnElement(operators.ColumnOperators, ClauseElement): else: return False + def cast(self, type_): + """Produce a type cast, i.e. ``CAST(<expression> AS <type>)``. + + This is a shortcut to the :func:`~.expression.cast` function. + + .. versionadded:: 1.0.7 + + """ + return Cast(self, type_) + def label(self, name): """Produce a column label, i.e. ``<columnname> AS <name>``. @@ -1128,8 +1086,7 @@ class BindParameter(ColumnElement): _compared_to_type.coerce_compared_value( _compared_to_operator, value) else: - self.type = type_api._type_map.get(type(value), - type_api.NULLTYPE) + self.type = type_api._resolve_value_to_type(value) elif isinstance(type_, type): self.type = type_() else: @@ -1144,8 +1101,7 @@ class BindParameter(ColumnElement): cloned.callable = None cloned.required = False if cloned.type is type_api.NULLTYPE: - cloned.type = type_api._type_map.get(type(value), - type_api.NULLTYPE) + cloned.type = type_api._resolve_value_to_type(value) return cloned @property @@ -1840,9 +1796,12 @@ class BooleanClauseList(ClauseList, ColumnElement): def _construct(cls, operator, continue_on, skip_on, *clauses, **kw): convert_clauses = [] - clauses = util.coerce_generator_arg(clauses) + clauses = [ + _expression_literal_as_text(clause) + for clause in + util.coerce_generator_arg(clauses) + ] for clause in clauses: - clause = _expression_literal_as_text(clause) if isinstance(clause, continue_on): continue @@ -2327,6 +2286,109 @@ class Cast(ColumnElement): return self.clause._from_objects +class TypeCoerce(ColumnElement): + """Represent a Python-side type-coercion wrapper. + + :class:`.TypeCoerce` supplies the :func:`.expression.type_coerce` + function; see that function for usage details. + + .. versionchanged:: 1.1 The :func:`.type_coerce` function now produces + a persistent :class:`.TypeCoerce` wrapper object rather than + translating the given object in place. + + .. seealso:: + + :func:`.expression.type_coerce` + + """ + + __visit_name__ = 'type_coerce' + + def __init__(self, expression, type_): + """Associate a SQL expression with a particular type, without rendering + ``CAST``. + + E.g.:: + + from sqlalchemy import type_coerce + + stmt = select([ + type_coerce(log_table.date_string, StringDateTime()) + ]) + + The above construct will produce a :class:`.TypeCoerce` object, which + renders SQL that labels the expression, but otherwise does not + modify its value on the SQL side:: + + SELECT date_string AS anon_1 FROM log + + When result rows are fetched, the ``StringDateTime`` type + will be applied to result rows on behalf of the ``date_string`` column. + The rationale for the "anon_1" label is so that the type-coerced + column remains separate in the list of result columns vs. other + type-coerced or direct values of the target column. In order to + provide a named label for the expression, use + :meth:`.ColumnElement.label`:: + + stmt = select([ + type_coerce( + log_table.date_string, StringDateTime()).label('date') + ]) + + + A type that features bound-value handling will also have that behavior + take effect when literal values or :func:`.bindparam` constructs are + passed to :func:`.type_coerce` as targets. + For example, if a type implements the + :meth:`.TypeEngine.bind_expression` + method or :meth:`.TypeEngine.bind_processor` method or equivalent, + these functions will take effect at statement compilation/execution + time when a literal value is passed, as in:: + + # bound-value handling of MyStringType will be applied to the + # literal value "some string" + stmt = select([type_coerce("some string", MyStringType)]) + + :func:`.type_coerce` is similar to the :func:`.cast` function, + except that it does not render the ``CAST`` expression in the resulting + statement. + + :param expression: A SQL expression, such as a :class:`.ColumnElement` + expression or a Python string which will be coerced into a bound + literal value. + + :param type_: A :class:`.TypeEngine` class or instance indicating + the type to which the expression is coerced. + + .. seealso:: + + :func:`.cast` + + """ + self.type = type_api.to_instance(type_) + self.clause = _literal_as_binds(expression, type_=self.type) + + def _copy_internals(self, clone=_clone, **kw): + self.clause = clone(self.clause, **kw) + self.__dict__.pop('typed_expression', None) + + def get_children(self, **kwargs): + return self.clause, + + @property + def _from_objects(self): + return self.clause._from_objects + + @util.memoized_property + def typed_expression(self): + if isinstance(self.clause, BindParameter): + bp = self.clause._clone() + bp.type = self.type + return bp + else: + return self.clause + + class Extract(ColumnElement): """Represent a SQL EXTRACT clause, ``extract(field FROM expr)``.""" @@ -2668,6 +2730,91 @@ class UnaryExpression(ColumnElement): return self +class CollectionAggregate(UnaryExpression): + """Forms the basis for right-hand collection operator modifiers + ANY and ALL. + + The ANY and ALL keywords are available in different ways on different + backends. On Postgresql, they only work for an ARRAY type. On + MySQL, they only work for subqueries. + + """ + @classmethod + def _create_any(cls, expr): + """Produce an ANY expression. + + This may apply to an array type for some dialects (e.g. postgresql), + or to a subquery for others (e.g. mysql). e.g.:: + + # postgresql '5 = ANY (somearray)' + expr = 5 == any_(mytable.c.somearray) + + # mysql '5 = ANY (SELECT value FROM table)' + expr = 5 == any_(select([table.c.value])) + + .. versionadded:: 1.1 + + .. seealso:: + + :func:`.expression.all_` + + """ + + expr = _literal_as_binds(expr) + + if expr.is_selectable and hasattr(expr, 'as_scalar'): + expr = expr.as_scalar() + expr = expr.self_group() + return CollectionAggregate( + expr, operator=operators.any_op, + type_=type_api.NULLTYPE, wraps_column_expression=False) + + @classmethod + def _create_all(cls, expr): + """Produce an ALL expression. + + This may apply to an array type for some dialects (e.g. postgresql), + or to a subquery for others (e.g. mysql). e.g.:: + + # postgresql '5 = ALL (somearray)' + expr = 5 == all_(mytable.c.somearray) + + # mysql '5 = ALL (SELECT value FROM table)' + expr = 5 == all_(select([table.c.value])) + + .. versionadded:: 1.1 + + .. seealso:: + + :func:`.expression.any_` + + """ + + expr = _literal_as_binds(expr) + if expr.is_selectable and hasattr(expr, 'as_scalar'): + expr = expr.as_scalar() + expr = expr.self_group() + return CollectionAggregate( + expr, operator=operators.all_op, + type_=type_api.NULLTYPE, wraps_column_expression=False) + + # operate and reverse_operate are hardwired to + # dispatch onto the type comparator directly, so that we can + # ensure "reversed" behavior. + def operate(self, op, *other, **kwargs): + if not operators.is_comparison(op): + raise exc.ArgumentError( + "Only comparison operators may be used with ANY/ALL") + kwargs['reverse'] = True + return self.comparator.operate(operators.mirror(op), *other, **kwargs) + + def reverse_operate(self, op, other, **kwargs): + # comparison operators should never call reverse_operate + assert not operators.is_comparison(op) + raise exc.ArgumentError( + "Only comparison operators may be used with ANY/ALL") + + class AsBoolean(UnaryExpression): def __init__(self, element, operator, negate): @@ -2779,6 +2926,32 @@ class BinaryExpression(ColumnElement): return super(BinaryExpression, self)._negate() +class Slice(ColumnElement): + """Represent SQL for a Python array-slice object. + + This is not a specific SQL construct at this level, but + may be interpreted by specific dialects, e.g. Postgresql. + + """ + __visit_name__ = 'slice' + + def __init__(self, start, stop, step): + self.start = start + self.stop = stop + self.step = step + self.type = type_api.NULLTYPE + + def self_group(self, against=None): + assert against is operator.getitem + return self + + +class IndexExpression(BinaryExpression): + """Represent the class of expressions that are like an "index" operation. + """ + pass + + class Grouping(ColumnElement): """Represent a grouping within a column expression""" @@ -2839,21 +3012,21 @@ class Over(ColumnElement): order_by = None partition_by = None - def __init__(self, func, partition_by=None, order_by=None): + def __init__(self, element, partition_by=None, order_by=None): """Produce an :class:`.Over` object against a function. Used against aggregate or so-called "window" functions, for database backends that support window functions. - E.g.:: + :func:`~.expression.over` is usually called using + the :meth:`.FunctionElement.over` method, e.g.:: - from sqlalchemy import over - over(func.row_number(), order_by='x') + func.row_number().over(order_by='x') - Would produce "ROW_NUMBER() OVER(ORDER BY x)". + Would produce ``ROW_NUMBER() OVER(ORDER BY x)``. - :param func: a :class:`.FunctionElement` construct, typically - generated by :data:`~.expression.func`. + :param element: a :class:`.FunctionElement`, :class:`.WithinGroup`, + or other compatible construct. :param partition_by: a column element or string, or a list of such, that will be used as the PARTITION BY clause of the OVER construct. @@ -2866,8 +3039,14 @@ class Over(ColumnElement): .. versionadded:: 0.7 + .. seealso:: + + :data:`.expression.func` + + :func:`.expression.within_group` + """ - self.func = func + self.element = element if order_by is not None: self.order_by = ClauseList( *util.to_list(order_by), @@ -2877,17 +3056,29 @@ class Over(ColumnElement): *util.to_list(partition_by), _literal_as_text=_literal_as_label_reference) + @property + def func(self): + """the element referred to by this :class:`.Over` + clause. + + .. deprecated:: 1.1 the ``func`` element has been renamed to + ``.element``. The two attributes are synonymous though + ``.func`` is read-only. + + """ + return self.element + @util.memoized_property def type(self): - return self.func.type + return self.element.type def get_children(self, **kwargs): return [c for c in - (self.func, self.partition_by, self.order_by) + (self.element, self.partition_by, self.order_by) if c is not None] def _copy_internals(self, clone=_clone, **kw): - self.func = clone(self.func, **kw) + self.element = clone(self.element, **kw) if self.partition_by is not None: self.partition_by = clone(self.partition_by, **kw) if self.order_by is not None: @@ -2897,7 +3088,106 @@ class Over(ColumnElement): def _from_objects(self): return list(itertools.chain( *[c._from_objects for c in - (self.func, self.partition_by, self.order_by) + (self.element, self.partition_by, self.order_by) + if c is not None] + )) + + +class WithinGroup(ColumnElement): + """Represent a WITHIN GROUP (ORDER BY) clause. + + This is a special operator against so-called + so-called "ordered set aggregate" and "hypothetical + set aggregate" functions, including ``percentile_cont()``, + ``rank()``, ``dense_rank()``, etc. + + It's supported only by certain database backends, such as PostgreSQL, + Oracle and MS SQL Server. + + The :class:`.WithinGroup` consturct extracts its type from the + method :meth:`.FunctionElement.within_group_type`. If this returns + ``None``, the function's ``.type`` is used. + + """ + __visit_name__ = 'withingroup' + + order_by = None + + def __init__(self, element, *order_by): + """Produce a :class:`.WithinGroup` object against a function. + + Used against so-called "ordered set aggregate" and "hypothetical + set aggregate" functions, including :class:`.percentile_cont`, + :class:`.rank`, :class:`.dense_rank`, etc. + + :func:`~.expression.within_group` is usually called using + the :meth:`.FunctionElement.within_group` method, e.g.:: + + from sqlalchemy import within_group + stmt = select([ + department.c.id, + func.percentile_cont(0.5).within_group( + department.c.salary.desc() + ) + ]) + + The above statement would produce SQL similar to + ``SELECT department.id, percentile_cont(0.5) + WITHIN GROUP (ORDER BY department.salary DESC)``. + + :param element: a :class:`.FunctionElement` construct, typically + generated by :data:`~.expression.func`. + :param \*order_by: one or more column elements that will be used + as the ORDER BY clause of the WITHIN GROUP construct. + + .. versionadded:: 1.1 + + .. seealso:: + + :data:`.expression.func` + + :func:`.expression.over` + + """ + self.element = element + if order_by is not None: + self.order_by = ClauseList( + *util.to_list(order_by), + _literal_as_text=_literal_as_label_reference) + + def over(self, partition_by=None, order_by=None): + """Produce an OVER clause against this :class:`.WithinGroup` + construct. + + This function has the same signature as that of + :meth:`.FunctionElement.over`. + + """ + return Over(self, partition_by=partition_by, order_by=order_by) + + @util.memoized_property + def type(self): + wgt = self.element.within_group_type(self) + if wgt is not None: + return wgt + else: + return self.element.type + + def get_children(self, **kwargs): + return [c for c in + (self.func, self.order_by) + if c is not None] + + def _copy_internals(self, clone=_clone, **kw): + self.element = clone(self.element, **kw) + if self.order_by is not None: + self.order_by = clone(self.order_by, **kw) + + @property + def _from_objects(self): + return list(itertools.chain( + *[c._from_objects for c in + (self.element, self.order_by) if c is not None] )) |