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# sql/default_comparator.py
# Copyright (C) 2005-2016 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
"""Default implementation of SQL comparison operations.
"""
from .. import exc, util
from . import type_api
from . import operators
from .elements import BindParameter, True_, False_, BinaryExpression, \
Null, _const_expr, _clause_element_as_expr, \
ClauseList, ColumnElement, TextClause, UnaryExpression, \
collate, _is_literal, _literal_as_text, ClauseElement, and_, or_
from .selectable import SelectBase, Alias, Selectable, ScalarSelect
def _boolean_compare(expr, op, obj, negate=None, reverse=False,
_python_is_types=(util.NoneType, bool),
result_type = None,
**kwargs):
if result_type is None:
result_type = type_api.BOOLEANTYPE
if isinstance(obj, _python_is_types + (Null, True_, False_)):
# allow x ==/!= True/False to be treated as a literal.
# this comes out to "== / != true/false" or "1/0" if those
# constants aren't supported and works on all platforms
if op in (operators.eq, operators.ne) and \
isinstance(obj, (bool, True_, False_)):
return BinaryExpression(expr,
_literal_as_text(obj),
op,
type_=result_type,
negate=negate, modifiers=kwargs)
else:
# all other None/True/False uses IS, IS NOT
if op in (operators.eq, operators.is_):
return BinaryExpression(expr, _const_expr(obj),
operators.is_,
negate=operators.isnot)
elif op in (operators.ne, operators.isnot):
return BinaryExpression(expr, _const_expr(obj),
operators.isnot,
negate=operators.is_)
else:
raise exc.ArgumentError(
"Only '=', '!=', 'is_()', 'isnot()' operators can "
"be used with None/True/False")
else:
obj = _check_literal(expr, op, obj)
if reverse:
return BinaryExpression(obj,
expr,
op,
type_=result_type,
negate=negate, modifiers=kwargs)
else:
return BinaryExpression(expr,
obj,
op,
type_=result_type,
negate=negate, modifiers=kwargs)
def _binary_operate(expr, op, obj, reverse=False, result_type=None,
**kw):
obj = _check_literal(expr, op, obj)
if reverse:
left, right = obj, expr
else:
left, right = expr, obj
if result_type is None:
op, result_type = left.comparator._adapt_expression(
op, right.comparator)
return BinaryExpression(
left, right, op, type_=result_type, modifiers=kw)
def _conjunction_operate(expr, op, other, **kw):
if op is operators.and_:
return and_(expr, other)
elif op is operators.or_:
return or_(expr, other)
else:
raise NotImplementedError()
def _scalar(expr, op, fn, **kw):
return fn(expr)
def _in_impl(expr, op, seq_or_selectable, negate_op, **kw):
seq_or_selectable = _clause_element_as_expr(seq_or_selectable)
if isinstance(seq_or_selectable, ScalarSelect):
return _boolean_compare(expr, op, seq_or_selectable,
negate=negate_op)
elif isinstance(seq_or_selectable, SelectBase):
# TODO: if we ever want to support (x, y, z) IN (select x,
# y, z from table), we would need a multi-column version of
# as_scalar() to produce a multi- column selectable that
# does not export itself as a FROM clause
return _boolean_compare(
expr, op, seq_or_selectable.as_scalar(),
negate=negate_op, **kw)
elif isinstance(seq_or_selectable, (Selectable, TextClause)):
return _boolean_compare(expr, op, seq_or_selectable,
negate=negate_op, **kw)
elif isinstance(seq_or_selectable, ClauseElement):
raise exc.InvalidRequestError(
'in_() accepts'
' either a list of expressions '
'or a selectable: %r' % seq_or_selectable)
# Handle non selectable arguments as sequences
args = []
for o in seq_or_selectable:
if not _is_literal(o):
if not isinstance(o, operators.ColumnOperators):
raise exc.InvalidRequestError(
'in_() accepts'
' either a list of expressions '
'or a selectable: %r' % o)
elif o is None:
o = Null()
else:
o = expr._bind_param(op, o)
args.append(o)
if len(args) == 0:
# Special case handling for empty IN's, behave like
# comparison against zero row selectable. We use != to
# build the contradiction as it handles NULL values
# appropriately, i.e. "not (x IN ())" should not return NULL
# values for x.
util.warn('The IN-predicate on "%s" was invoked with an '
'empty sequence. This results in a '
'contradiction, which nonetheless can be '
'expensive to evaluate. Consider alternative '
'strategies for improved performance.' % expr)
if op is operators.in_op:
return expr != expr
else:
return expr == expr
return _boolean_compare(expr, op,
ClauseList(*args).self_group(against=op),
negate=negate_op)
def _unsupported_impl(expr, op, *arg, **kw):
raise NotImplementedError("Operator '%s' is not supported on "
"this expression" % op.__name__)
def _inv_impl(expr, op, **kw):
"""See :meth:`.ColumnOperators.__inv__`."""
if hasattr(expr, 'negation_clause'):
return expr.negation_clause
else:
return expr._negate()
def _neg_impl(expr, op, **kw):
"""See :meth:`.ColumnOperators.__neg__`."""
return UnaryExpression(expr, operator=operators.neg, type_=expr.type)
def _match_impl(expr, op, other, **kw):
"""See :meth:`.ColumnOperators.match`."""
return _boolean_compare(
expr, operators.match_op,
_check_literal(
expr, operators.match_op, other),
result_type=type_api.MATCHTYPE,
negate=operators.notmatch_op
if op is operators.match_op else operators.match_op,
**kw
)
def _distinct_impl(expr, op, **kw):
"""See :meth:`.ColumnOperators.distinct`."""
return UnaryExpression(expr, operator=operators.distinct_op,
type_=expr.type)
def _between_impl(expr, op, cleft, cright, **kw):
"""See :meth:`.ColumnOperators.between`."""
return BinaryExpression(
expr,
ClauseList(
_check_literal(expr, operators.and_, cleft),
_check_literal(expr, operators.and_, cright),
operator=operators.and_,
group=False, group_contents=False),
op,
negate=operators.notbetween_op
if op is operators.between_op
else operators.between_op,
modifiers=kw)
def _collate_impl(expr, op, other, **kw):
return collate(expr, other)
# a mapping of operators with the method they use, along with
# their negated operator for comparison operators
operator_lookup = {
"and_": (_conjunction_operate,),
"or_": (_conjunction_operate,),
"inv": (_inv_impl,),
"add": (_binary_operate,),
"mul": (_binary_operate,),
"sub": (_binary_operate,),
"div": (_binary_operate,),
"mod": (_binary_operate,),
"truediv": (_binary_operate,),
"custom_op": (_binary_operate,),
"concat_op": (_binary_operate,),
"lt": (_boolean_compare, operators.ge),
"le": (_boolean_compare, operators.gt),
"ne": (_boolean_compare, operators.eq),
"gt": (_boolean_compare, operators.le),
"ge": (_boolean_compare, operators.lt),
"eq": (_boolean_compare, operators.ne),
"like_op": (_boolean_compare, operators.notlike_op),
"ilike_op": (_boolean_compare, operators.notilike_op),
"notlike_op": (_boolean_compare, operators.like_op),
"notilike_op": (_boolean_compare, operators.ilike_op),
"contains_op": (_boolean_compare, operators.notcontains_op),
"startswith_op": (_boolean_compare, operators.notstartswith_op),
"endswith_op": (_boolean_compare, operators.notendswith_op),
"desc_op": (_scalar, UnaryExpression._create_desc),
"asc_op": (_scalar, UnaryExpression._create_asc),
"nullsfirst_op": (_scalar, UnaryExpression._create_nullsfirst),
"nullslast_op": (_scalar, UnaryExpression._create_nullslast),
"in_op": (_in_impl, operators.notin_op),
"notin_op": (_in_impl, operators.in_op),
"is_": (_boolean_compare, operators.is_),
"isnot": (_boolean_compare, operators.isnot),
"collate": (_collate_impl,),
"match_op": (_match_impl,),
"notmatch_op": (_match_impl,),
"distinct_op": (_distinct_impl,),
"between_op": (_between_impl, ),
"notbetween_op": (_between_impl, ),
"neg": (_neg_impl,),
"getitem": (_unsupported_impl,),
"lshift": (_unsupported_impl,),
"rshift": (_unsupported_impl,),
"contains": (_unsupported_impl,),
}
def _check_literal(expr, operator, other):
if isinstance(other, (ColumnElement, TextClause)):
if isinstance(other, BindParameter) and \
other.type._isnull:
other = other._clone()
other.type = expr.type
return other
elif hasattr(other, '__clause_element__'):
other = other.__clause_element__()
elif isinstance(other, type_api.TypeEngine.Comparator):
other = other.expr
if isinstance(other, (SelectBase, Alias)):
return other.as_scalar()
elif not isinstance(other, (ColumnElement, TextClause)):
return expr._bind_param(operator, other)
else:
return other
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