309 lines
11 KiB
Python
309 lines
11 KiB
Python
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# sql/default_comparator.py
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# Copyright (C) 2005-2017 the SQLAlchemy authors and contributors
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# <see AUTHORS file>
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#
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# This module is part of SQLAlchemy and is released under
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# the MIT License: http://www.opensource.org/licenses/mit-license.php
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"""Default implementation of SQL comparison operations.
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"""
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from .. import exc, util
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from . import type_api
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from . import operators
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from .elements import BindParameter, True_, False_, BinaryExpression, \
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Null, _const_expr, _clause_element_as_expr, \
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ClauseList, ColumnElement, TextClause, UnaryExpression, \
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collate, _is_literal, _literal_as_text, ClauseElement, and_, or_, \
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Slice, Visitable, _literal_as_binds
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from .selectable import SelectBase, Alias, Selectable, ScalarSelect
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def _boolean_compare(expr, op, obj, negate=None, reverse=False,
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_python_is_types=(util.NoneType, bool),
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result_type = None,
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**kwargs):
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if result_type is None:
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result_type = type_api.BOOLEANTYPE
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if isinstance(obj, _python_is_types + (Null, True_, False_)):
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# allow x ==/!= True/False to be treated as a literal.
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# this comes out to "== / != true/false" or "1/0" if those
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# constants aren't supported and works on all platforms
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if op in (operators.eq, operators.ne) and \
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isinstance(obj, (bool, True_, False_)):
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return BinaryExpression(expr,
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_literal_as_text(obj),
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op,
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type_=result_type,
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negate=negate, modifiers=kwargs)
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elif op in (operators.is_distinct_from, operators.isnot_distinct_from):
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return BinaryExpression(expr,
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_literal_as_text(obj),
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op,
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type_=result_type,
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negate=negate, modifiers=kwargs)
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else:
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# all other None/True/False uses IS, IS NOT
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if op in (operators.eq, operators.is_):
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return BinaryExpression(expr, _const_expr(obj),
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operators.is_,
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negate=operators.isnot)
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elif op in (operators.ne, operators.isnot):
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return BinaryExpression(expr, _const_expr(obj),
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operators.isnot,
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negate=operators.is_)
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else:
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raise exc.ArgumentError(
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"Only '=', '!=', 'is_()', 'isnot()', "
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"'is_distinct_from()', 'isnot_distinct_from()' "
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"operators can be used with None/True/False")
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else:
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obj = _check_literal(expr, op, obj)
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if reverse:
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return BinaryExpression(obj,
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expr,
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op,
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type_=result_type,
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negate=negate, modifiers=kwargs)
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else:
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return BinaryExpression(expr,
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obj,
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op,
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type_=result_type,
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negate=negate, modifiers=kwargs)
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def _binary_operate(expr, op, obj, reverse=False, result_type=None,
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**kw):
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obj = _check_literal(expr, op, obj)
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if reverse:
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left, right = obj, expr
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else:
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left, right = expr, obj
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if result_type is None:
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op, result_type = left.comparator._adapt_expression(
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op, right.comparator)
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return BinaryExpression(
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left, right, op, type_=result_type, modifiers=kw)
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def _conjunction_operate(expr, op, other, **kw):
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if op is operators.and_:
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return and_(expr, other)
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elif op is operators.or_:
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return or_(expr, other)
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else:
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raise NotImplementedError()
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def _scalar(expr, op, fn, **kw):
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return fn(expr)
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def _in_impl(expr, op, seq_or_selectable, negate_op, **kw):
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seq_or_selectable = _clause_element_as_expr(seq_or_selectable)
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if isinstance(seq_or_selectable, ScalarSelect):
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return _boolean_compare(expr, op, seq_or_selectable,
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negate=negate_op)
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elif isinstance(seq_or_selectable, SelectBase):
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# TODO: if we ever want to support (x, y, z) IN (select x,
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# y, z from table), we would need a multi-column version of
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# as_scalar() to produce a multi- column selectable that
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# does not export itself as a FROM clause
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return _boolean_compare(
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expr, op, seq_or_selectable.as_scalar(),
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negate=negate_op, **kw)
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elif isinstance(seq_or_selectable, (Selectable, TextClause)):
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return _boolean_compare(expr, op, seq_or_selectable,
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negate=negate_op, **kw)
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elif isinstance(seq_or_selectable, ClauseElement):
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raise exc.InvalidRequestError(
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'in_() accepts'
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' either a list of expressions '
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'or a selectable: %r' % seq_or_selectable)
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# Handle non selectable arguments as sequences
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args = []
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for o in seq_or_selectable:
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if not _is_literal(o):
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if not isinstance(o, operators.ColumnOperators):
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raise exc.InvalidRequestError(
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'in_() accepts'
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' either a list of expressions '
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'or a selectable: %r' % o)
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elif o is None:
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o = Null()
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else:
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o = expr._bind_param(op, o)
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args.append(o)
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if len(args) == 0:
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# Special case handling for empty IN's, behave like
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# comparison against zero row selectable. We use != to
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# build the contradiction as it handles NULL values
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# appropriately, i.e. "not (x IN ())" should not return NULL
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# values for x.
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util.warn('The IN-predicate on "%s" was invoked with an '
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'empty sequence. This results in a '
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'contradiction, which nonetheless can be '
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'expensive to evaluate. Consider alternative '
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'strategies for improved performance.' % expr)
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if op is operators.in_op:
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return expr != expr
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else:
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return expr == expr
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return _boolean_compare(expr, op,
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ClauseList(*args).self_group(against=op),
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negate=negate_op)
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def _getitem_impl(expr, op, other, **kw):
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if isinstance(expr.type, type_api.INDEXABLE):
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other = _check_literal(expr, op, other)
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return _binary_operate(expr, op, other, **kw)
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else:
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_unsupported_impl(expr, op, other, **kw)
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def _unsupported_impl(expr, op, *arg, **kw):
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raise NotImplementedError("Operator '%s' is not supported on "
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"this expression" % op.__name__)
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def _inv_impl(expr, op, **kw):
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"""See :meth:`.ColumnOperators.__inv__`."""
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if hasattr(expr, 'negation_clause'):
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return expr.negation_clause
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else:
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return expr._negate()
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def _neg_impl(expr, op, **kw):
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"""See :meth:`.ColumnOperators.__neg__`."""
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return UnaryExpression(expr, operator=operators.neg, type_=expr.type)
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def _match_impl(expr, op, other, **kw):
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"""See :meth:`.ColumnOperators.match`."""
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return _boolean_compare(
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expr, operators.match_op,
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_check_literal(
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expr, operators.match_op, other),
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result_type=type_api.MATCHTYPE,
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negate=operators.notmatch_op
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if op is operators.match_op else operators.match_op,
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**kw
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)
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def _distinct_impl(expr, op, **kw):
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"""See :meth:`.ColumnOperators.distinct`."""
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return UnaryExpression(expr, operator=operators.distinct_op,
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type_=expr.type)
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def _between_impl(expr, op, cleft, cright, **kw):
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"""See :meth:`.ColumnOperators.between`."""
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return BinaryExpression(
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expr,
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ClauseList(
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_check_literal(expr, operators.and_, cleft),
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_check_literal(expr, operators.and_, cright),
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operator=operators.and_,
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group=False, group_contents=False),
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op,
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negate=operators.notbetween_op
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if op is operators.between_op
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else operators.between_op,
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modifiers=kw)
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def _collate_impl(expr, op, other, **kw):
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return collate(expr, other)
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# a mapping of operators with the method they use, along with
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# their negated operator for comparison operators
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operator_lookup = {
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"and_": (_conjunction_operate,),
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"or_": (_conjunction_operate,),
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"inv": (_inv_impl,),
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"add": (_binary_operate,),
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"mul": (_binary_operate,),
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"sub": (_binary_operate,),
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"div": (_binary_operate,),
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"mod": (_binary_operate,),
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"truediv": (_binary_operate,),
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"custom_op": (_binary_operate,),
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"json_path_getitem_op": (_binary_operate, ),
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"json_getitem_op": (_binary_operate, ),
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"concat_op": (_binary_operate,),
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"lt": (_boolean_compare, operators.ge),
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"le": (_boolean_compare, operators.gt),
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"ne": (_boolean_compare, operators.eq),
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"gt": (_boolean_compare, operators.le),
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"ge": (_boolean_compare, operators.lt),
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"eq": (_boolean_compare, operators.ne),
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"is_distinct_from": (_boolean_compare, operators.isnot_distinct_from),
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"isnot_distinct_from": (_boolean_compare, operators.is_distinct_from),
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"like_op": (_boolean_compare, operators.notlike_op),
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"ilike_op": (_boolean_compare, operators.notilike_op),
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"notlike_op": (_boolean_compare, operators.like_op),
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"notilike_op": (_boolean_compare, operators.ilike_op),
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"contains_op": (_boolean_compare, operators.notcontains_op),
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"startswith_op": (_boolean_compare, operators.notstartswith_op),
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"endswith_op": (_boolean_compare, operators.notendswith_op),
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"desc_op": (_scalar, UnaryExpression._create_desc),
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"asc_op": (_scalar, UnaryExpression._create_asc),
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"nullsfirst_op": (_scalar, UnaryExpression._create_nullsfirst),
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"nullslast_op": (_scalar, UnaryExpression._create_nullslast),
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"in_op": (_in_impl, operators.notin_op),
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"notin_op": (_in_impl, operators.in_op),
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"is_": (_boolean_compare, operators.is_),
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"isnot": (_boolean_compare, operators.isnot),
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"collate": (_collate_impl,),
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"match_op": (_match_impl,),
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"notmatch_op": (_match_impl,),
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"distinct_op": (_distinct_impl,),
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"between_op": (_between_impl, ),
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"notbetween_op": (_between_impl, ),
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"neg": (_neg_impl,),
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"getitem": (_getitem_impl,),
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"lshift": (_unsupported_impl,),
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"rshift": (_unsupported_impl,),
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"contains": (_unsupported_impl,),
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}
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def _check_literal(expr, operator, other, bindparam_type=None):
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if isinstance(other, (ColumnElement, TextClause)):
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if isinstance(other, BindParameter) and \
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other.type._isnull:
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other = other._clone()
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other.type = expr.type
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return other
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elif hasattr(other, '__clause_element__'):
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other = other.__clause_element__()
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elif isinstance(other, type_api.TypeEngine.Comparator):
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other = other.expr
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if isinstance(other, (SelectBase, Alias)):
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return other.as_scalar()
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elif not isinstance(other, Visitable):
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return expr._bind_param(operator, other, type_=bindparam_type)
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else:
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return other
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