# sql/traversals.py
# Copyright (C) 2005-2022 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: https://www.opensource.org/licenses/mit-license.php
# mypy: allow-untyped-defs, allow-untyped-calls

from __future__ import annotations

from collections import deque
import collections.abc as collections_abc
import itertools
from itertools import zip_longest
import operator
import typing
from typing import Any
from typing import Callable
from typing import Deque
from typing import Dict
from typing import Iterable
from typing import Optional
from typing import Set
from typing import Tuple
from typing import Type
from typing import TypeVar

from . import operators
from .cache_key import HasCacheKey
from .visitors import _TraverseInternalsType
from .visitors import anon_map
from .visitors import ExternallyTraversible
from .visitors import HasTraversalDispatch
from .visitors import HasTraverseInternals
from .. import util
from ..util import langhelpers

SKIP_TRAVERSE = util.symbol("skip_traverse")
COMPARE_FAILED = False
COMPARE_SUCCEEDED = True


def compare(obj1: Any, obj2: Any, **kw: Any) -> bool:
    strategy: TraversalComparatorStrategy
    if kw.get("use_proxies", False):
        strategy = ColIdentityComparatorStrategy()
    else:
        strategy = TraversalComparatorStrategy()

    return strategy.compare(obj1, obj2, **kw)


def _preconfigure_traversals(target_hierarchy: Type[Any]) -> None:
    for cls in util.walk_subclasses(target_hierarchy):
        if hasattr(cls, "_generate_cache_attrs") and hasattr(
            cls, "_traverse_internals"
        ):
            cls._generate_cache_attrs()  # type: ignore
            _copy_internals.generate_dispatch(
                cls,  # type: ignore
                cls._traverse_internals,  # type: ignore
                "_generated_copy_internals_traversal",
            )
            _get_children.generate_dispatch(
                cls,  # type: ignore
                cls._traverse_internals,  # type: ignore
                "_generated_get_children_traversal",
            )


SelfHasShallowCopy = TypeVar("SelfHasShallowCopy", bound="HasShallowCopy")


class HasShallowCopy(HasTraverseInternals):
    """attribute-wide operations that are useful for classes that use
    __slots__ and therefore can't operate on their attributes in a dictionary.


    """

    __slots__ = ()

    if typing.TYPE_CHECKING:

        def _generated_shallow_copy_traversal(
            self: SelfHasShallowCopy, other: SelfHasShallowCopy
        ) -> None:
            ...

        def _generated_shallow_from_dict_traversal(
            self, d: Dict[str, Any]
        ) -> None:
            ...

        def _generated_shallow_to_dict_traversal(self) -> Dict[str, Any]:
            ...

    @classmethod
    def _generate_shallow_copy(
        cls: Type[SelfHasShallowCopy],
        internal_dispatch: _TraverseInternalsType,
        method_name: str,
    ) -> Callable[[SelfHasShallowCopy, SelfHasShallowCopy], None]:
        code = "\n".join(
            f"    other.{attrname} = self.{attrname}"
            for attrname, _ in internal_dispatch
        )
        meth_text = f"def {method_name}(self, other):\n{code}\n"
        return langhelpers._exec_code_in_env(meth_text, {}, method_name)

    @classmethod
    def _generate_shallow_to_dict(
        cls: Type[SelfHasShallowCopy],
        internal_dispatch: _TraverseInternalsType,
        method_name: str,
    ) -> Callable[[SelfHasShallowCopy], Dict[str, Any]]:
        code = ",\n".join(
            f"    '{attrname}': self.{attrname}"
            for attrname, _ in internal_dispatch
        )
        meth_text = f"def {method_name}(self):\n    return {{{code}}}\n"
        return langhelpers._exec_code_in_env(meth_text, {}, method_name)

    @classmethod
    def _generate_shallow_from_dict(
        cls: Type[SelfHasShallowCopy],
        internal_dispatch: _TraverseInternalsType,
        method_name: str,
    ) -> Callable[[SelfHasShallowCopy, Dict[str, Any]], None]:
        code = "\n".join(
            f"    self.{attrname} = d['{attrname}']"
            for attrname, _ in internal_dispatch
        )
        meth_text = f"def {method_name}(self, d):\n{code}\n"
        return langhelpers._exec_code_in_env(meth_text, {}, method_name)

    def _shallow_from_dict(self, d: Dict[str, Any]) -> None:
        cls = self.__class__

        shallow_from_dict: Callable[[HasShallowCopy, Dict[str, Any]], None]
        try:
            shallow_from_dict = cls.__dict__[
                "_generated_shallow_from_dict_traversal"
            ]
        except KeyError:
            shallow_from_dict = self._generate_shallow_from_dict(
                cls._traverse_internals,
                "_generated_shallow_from_dict_traversal",
            )

            cls._generated_shallow_from_dict_traversal = shallow_from_dict  # type: ignore  # noqa: E501

        shallow_from_dict(self, d)

    def _shallow_to_dict(self) -> Dict[str, Any]:
        cls = self.__class__

        shallow_to_dict: Callable[[HasShallowCopy], Dict[str, Any]]

        try:
            shallow_to_dict = cls.__dict__[
                "_generated_shallow_to_dict_traversal"
            ]
        except KeyError:
            shallow_to_dict = self._generate_shallow_to_dict(
                cls._traverse_internals, "_generated_shallow_to_dict_traversal"
            )

            cls._generated_shallow_to_dict_traversal = shallow_to_dict  # type: ignore  # noqa: E501
        return shallow_to_dict(self)

    def _shallow_copy_to(
        self: SelfHasShallowCopy, other: SelfHasShallowCopy
    ) -> None:
        cls = self.__class__

        shallow_copy: Callable[[SelfHasShallowCopy, SelfHasShallowCopy], None]
        try:
            shallow_copy = cls.__dict__["_generated_shallow_copy_traversal"]
        except KeyError:
            shallow_copy = self._generate_shallow_copy(
                cls._traverse_internals, "_generated_shallow_copy_traversal"
            )

            cls._generated_shallow_copy_traversal = shallow_copy  # type: ignore  # noqa: E501
        shallow_copy(self, other)

    def _clone(self: SelfHasShallowCopy, **kw: Any) -> SelfHasShallowCopy:
        """Create a shallow copy"""
        c = self.__class__.__new__(self.__class__)
        self._shallow_copy_to(c)
        return c


SelfGenerativeOnTraversal = TypeVar(
    "SelfGenerativeOnTraversal", bound="GenerativeOnTraversal"
)


class GenerativeOnTraversal(HasShallowCopy):
    """Supplies Generative behavior but making use of traversals to shallow
    copy.

    .. seealso::

        :class:`sqlalchemy.sql.base.Generative`


    """

    __slots__ = ()

    def _generate(
        self: SelfGenerativeOnTraversal,
    ) -> SelfGenerativeOnTraversal:
        cls = self.__class__
        s = cls.__new__(cls)
        self._shallow_copy_to(s)
        return s


def _clone(element, **kw):
    return element._clone()


class HasCopyInternals(HasTraverseInternals):
    __slots__ = ()

    def _clone(self, **kw):
        raise NotImplementedError()

    def _copy_internals(
        self, *, omit_attrs: Iterable[str] = (), **kw: Any
    ) -> None:
        """Reassign internal elements to be clones of themselves.

        Called during a copy-and-traverse operation on newly
        shallow-copied elements to create a deep copy.

        The given clone function should be used, which may be applying
        additional transformations to the element (i.e. replacement
        traversal, cloned traversal, annotations).

        """

        try:
            traverse_internals = self._traverse_internals
        except AttributeError:
            # user-defined classes may not have a _traverse_internals
            return

        for attrname, obj, meth in _copy_internals.run_generated_dispatch(
            self, traverse_internals, "_generated_copy_internals_traversal"
        ):
            if attrname in omit_attrs:
                continue

            if obj is not None:
                result = meth(attrname, self, obj, **kw)
                if result is not None:
                    setattr(self, attrname, result)


class _CopyInternalsTraversal(HasTraversalDispatch):
    """Generate a _copy_internals internal traversal dispatch for classes
    with a _traverse_internals collection."""

    def visit_clauseelement(
        self, attrname, parent, element, clone=_clone, **kw
    ):
        return clone(element, **kw)

    def visit_clauseelement_list(
        self, attrname, parent, element, clone=_clone, **kw
    ):
        return [clone(clause, **kw) for clause in element]

    def visit_clauseelement_tuple(
        self, attrname, parent, element, clone=_clone, **kw
    ):
        return tuple([clone(clause, **kw) for clause in element])

    def visit_executable_options(
        self, attrname, parent, element, clone=_clone, **kw
    ):
        return tuple([clone(clause, **kw) for clause in element])

    def visit_clauseelement_unordered_set(
        self, attrname, parent, element, clone=_clone, **kw
    ):
        return {clone(clause, **kw) for clause in element}

    def visit_clauseelement_tuples(
        self, attrname, parent, element, clone=_clone, **kw
    ):
        return [
            tuple(clone(tup_elem, **kw) for tup_elem in elem)
            for elem in element
        ]

    def visit_string_clauseelement_dict(
        self, attrname, parent, element, clone=_clone, **kw
    ):
        return {key: clone(value, **kw) for key, value in element.items()}

    def visit_setup_join_tuple(
        self, attrname, parent, element, clone=_clone, **kw
    ):
        return tuple(
            (
                clone(target, **kw) if target is not None else None,
                clone(onclause, **kw) if onclause is not None else None,
                clone(from_, **kw) if from_ is not None else None,
                flags,
            )
            for (target, onclause, from_, flags) in element
        )

    def visit_memoized_select_entities(self, attrname, parent, element, **kw):
        return self.visit_clauseelement_tuple(attrname, parent, element, **kw)

    def visit_dml_ordered_values(
        self, attrname, parent, element, clone=_clone, **kw
    ):
        # sequence of 2-tuples
        return [
            (
                clone(key, **kw)
                if hasattr(key, "__clause_element__")
                else key,
                clone(value, **kw),
            )
            for key, value in element
        ]

    def visit_dml_values(self, attrname, parent, element, clone=_clone, **kw):
        return {
            (
                clone(key, **kw) if hasattr(key, "__clause_element__") else key
            ): clone(value, **kw)
            for key, value in element.items()
        }

    def visit_dml_multi_values(
        self, attrname, parent, element, clone=_clone, **kw
    ):
        # sequence of sequences, each sequence contains a list/dict/tuple

        def copy(elem):
            if isinstance(elem, (list, tuple)):
                return [
                    clone(value, **kw)
                    if hasattr(value, "__clause_element__")
                    else value
                    for value in elem
                ]
            elif isinstance(elem, dict):
                return {
                    (
                        clone(key, **kw)
                        if hasattr(key, "__clause_element__")
                        else key
                    ): (
                        clone(value, **kw)
                        if hasattr(value, "__clause_element__")
                        else value
                    )
                    for key, value in elem.items()
                }
            else:
                # TODO: use abc classes
                assert False

        return [
            [copy(sub_element) for sub_element in sequence]
            for sequence in element
        ]

    def visit_propagate_attrs(
        self, attrname, parent, element, clone=_clone, **kw
    ):
        return element


_copy_internals = _CopyInternalsTraversal()


def _flatten_clauseelement(element):
    while hasattr(element, "__clause_element__") and not getattr(
        element, "is_clause_element", False
    ):
        element = element.__clause_element__()

    return element


class _GetChildrenTraversal(HasTraversalDispatch):
    """Generate a _children_traversal internal traversal dispatch for classes
    with a _traverse_internals collection."""

    def visit_has_cache_key(self, element, **kw):
        # the GetChildren traversal refers explicitly to ClauseElement
        # structures.  Within these, a plain HasCacheKey is not a
        # ClauseElement, so don't include these.
        return ()

    def visit_clauseelement(self, element, **kw):
        return (element,)

    def visit_clauseelement_list(self, element, **kw):
        return element

    def visit_clauseelement_tuple(self, element, **kw):
        return element

    def visit_clauseelement_tuples(self, element, **kw):
        return itertools.chain.from_iterable(element)

    def visit_fromclause_canonical_column_collection(self, element, **kw):
        return ()

    def visit_string_clauseelement_dict(self, element, **kw):
        return element.values()

    def visit_fromclause_ordered_set(self, element, **kw):
        return element

    def visit_clauseelement_unordered_set(self, element, **kw):
        return element

    def visit_setup_join_tuple(self, element, **kw):
        for (target, onclause, from_, flags) in element:
            if from_ is not None:
                yield from_

            if not isinstance(target, str):
                yield _flatten_clauseelement(target)

            if onclause is not None and not isinstance(onclause, str):
                yield _flatten_clauseelement(onclause)

    def visit_memoized_select_entities(self, element, **kw):
        return self.visit_clauseelement_tuple(element, **kw)

    def visit_dml_ordered_values(self, element, **kw):
        for k, v in element:
            if hasattr(k, "__clause_element__"):
                yield k
            yield v

    def visit_dml_values(self, element, **kw):
        expr_values = {k for k in element if hasattr(k, "__clause_element__")}
        str_values = expr_values.symmetric_difference(element)

        for k in sorted(str_values):
            yield element[k]
        for k in expr_values:
            yield k
            yield element[k]

    def visit_dml_multi_values(self, element, **kw):
        return ()

    def visit_propagate_attrs(self, element, **kw):
        return ()


_get_children = _GetChildrenTraversal()


@util.preload_module("sqlalchemy.sql.elements")
def _resolve_name_for_compare(element, name, anon_map, **kw):
    if isinstance(name, util.preloaded.sql_elements._anonymous_label):
        name = name.apply_map(anon_map)

    return name


class TraversalComparatorStrategy(HasTraversalDispatch, util.MemoizedSlots):
    __slots__ = "stack", "cache", "anon_map"

    def __init__(self):
        self.stack: Deque[
            Tuple[
                Optional[ExternallyTraversible],
                Optional[ExternallyTraversible],
            ]
        ] = deque()
        self.cache = set()

    def _memoized_attr_anon_map(self):
        return (anon_map(), anon_map())

    def compare(
        self,
        obj1: ExternallyTraversible,
        obj2: ExternallyTraversible,
        **kw: Any,
    ) -> bool:
        stack = self.stack
        cache = self.cache

        compare_annotations = kw.get("compare_annotations", False)

        stack.append((obj1, obj2))

        while stack:
            left, right = stack.popleft()

            if left is right:
                continue
            elif left is None or right is None:
                # we know they are different so no match
                return False
            elif (left, right) in cache:
                continue
            cache.add((left, right))

            visit_name = left.__visit_name__
            if visit_name != right.__visit_name__:
                return False

            meth = getattr(self, "compare_%s" % visit_name, None)

            if meth:
                attributes_compared = meth(left, right, **kw)
                if attributes_compared is COMPARE_FAILED:
                    return False
                elif attributes_compared is SKIP_TRAVERSE:
                    continue

                # attributes_compared is returned as a list of attribute
                # names that were "handled" by the comparison method above.
                # remaining attribute names in the _traverse_internals
                # will be compared.
            else:
                attributes_compared = ()

            for (
                (left_attrname, left_visit_sym),
                (right_attrname, right_visit_sym),
            ) in zip_longest(
                left._traverse_internals,
                right._traverse_internals,
                fillvalue=(None, None),
            ):
                if not compare_annotations and (
                    (left_attrname == "_annotations")
                    or (right_attrname == "_annotations")
                ):
                    continue

                if (
                    left_attrname != right_attrname
                    or left_visit_sym is not right_visit_sym
                ):
                    return False
                elif left_attrname in attributes_compared:
                    continue

                assert left_visit_sym is not None
                assert left_attrname is not None
                assert right_attrname is not None

                dispatch = self.dispatch(left_visit_sym)
                assert dispatch is not None, (
                    f"{self.__class__} has no dispatch for "
                    f"'{self._dispatch_lookup[left_visit_sym]}'"
                )
                left_child = operator.attrgetter(left_attrname)(left)
                right_child = operator.attrgetter(right_attrname)(right)
                if left_child is None:
                    if right_child is not None:
                        return False
                    else:
                        continue

                comparison = dispatch(
                    left_attrname, left, left_child, right, right_child, **kw
                )
                if comparison is COMPARE_FAILED:
                    return False

        return True

    def compare_inner(self, obj1, obj2, **kw):
        comparator = self.__class__()
        return comparator.compare(obj1, obj2, **kw)

    def visit_has_cache_key(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        if left._gen_cache_key(self.anon_map[0], []) != right._gen_cache_key(
            self.anon_map[1], []
        ):
            return COMPARE_FAILED

    def visit_propagate_attrs(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        return self.compare_inner(
            left.get("plugin_subject", None), right.get("plugin_subject", None)
        )

    def visit_has_cache_key_list(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        for l, r in zip_longest(left, right, fillvalue=None):
            if l is None:
                if r is not None:
                    return COMPARE_FAILED
                else:
                    continue
            elif r is None:
                return COMPARE_FAILED

            if l._gen_cache_key(self.anon_map[0], []) != r._gen_cache_key(
                self.anon_map[1], []
            ):
                return COMPARE_FAILED

    def visit_executable_options(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        for l, r in zip_longest(left, right, fillvalue=None):
            if l is None:
                if r is not None:
                    return COMPARE_FAILED
                else:
                    continue
            elif r is None:
                return COMPARE_FAILED

            if (
                l._gen_cache_key(self.anon_map[0], [])
                if l._is_has_cache_key
                else l
            ) != (
                r._gen_cache_key(self.anon_map[1], [])
                if r._is_has_cache_key
                else r
            ):
                return COMPARE_FAILED

    def visit_clauseelement(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        self.stack.append((left, right))

    def visit_fromclause_canonical_column_collection(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        for lcol, rcol in zip_longest(left, right, fillvalue=None):
            self.stack.append((lcol, rcol))

    def visit_fromclause_derived_column_collection(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        pass

    def visit_string_clauseelement_dict(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        for lstr, rstr in zip_longest(
            sorted(left), sorted(right), fillvalue=None
        ):
            if lstr != rstr:
                return COMPARE_FAILED
            self.stack.append((left[lstr], right[rstr]))

    def visit_clauseelement_tuples(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        for ltup, rtup in zip_longest(left, right, fillvalue=None):
            if ltup is None or rtup is None:
                return COMPARE_FAILED

            for l, r in zip_longest(ltup, rtup, fillvalue=None):
                self.stack.append((l, r))

    def visit_clauseelement_list(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        for l, r in zip_longest(left, right, fillvalue=None):
            self.stack.append((l, r))

    def visit_clauseelement_tuple(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        for l, r in zip_longest(left, right, fillvalue=None):
            self.stack.append((l, r))

    def _compare_unordered_sequences(self, seq1, seq2, **kw):
        if seq1 is None:
            return seq2 is None

        completed: Set[object] = set()
        for clause in seq1:
            for other_clause in set(seq2).difference(completed):
                if self.compare_inner(clause, other_clause, **kw):
                    completed.add(other_clause)
                    break
        return len(completed) == len(seq1) == len(seq2)

    def visit_clauseelement_unordered_set(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        return self._compare_unordered_sequences(left, right, **kw)

    def visit_fromclause_ordered_set(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        for l, r in zip_longest(left, right, fillvalue=None):
            self.stack.append((l, r))

    def visit_string(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        return left == right

    def visit_string_list(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        return left == right

    def visit_string_multi_dict(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):

        for lk, rk in zip_longest(
            sorted(left.keys()), sorted(right.keys()), fillvalue=(None, None)
        ):
            if lk != rk:
                return COMPARE_FAILED

            lv, rv = left[lk], right[rk]

            lhc = isinstance(left, HasCacheKey)
            rhc = isinstance(right, HasCacheKey)
            if lhc and rhc:
                if lv._gen_cache_key(
                    self.anon_map[0], []
                ) != rv._gen_cache_key(self.anon_map[1], []):
                    return COMPARE_FAILED
            elif lhc != rhc:
                return COMPARE_FAILED
            elif lv != rv:
                return COMPARE_FAILED

    def visit_multi(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):

        lhc = isinstance(left, HasCacheKey)
        rhc = isinstance(right, HasCacheKey)
        if lhc and rhc:
            if left._gen_cache_key(
                self.anon_map[0], []
            ) != right._gen_cache_key(self.anon_map[1], []):
                return COMPARE_FAILED
        elif lhc != rhc:
            return COMPARE_FAILED
        else:
            return left == right

    def visit_anon_name(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        return _resolve_name_for_compare(
            left_parent, left, self.anon_map[0], **kw
        ) == _resolve_name_for_compare(
            right_parent, right, self.anon_map[1], **kw
        )

    def visit_boolean(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        return left == right

    def visit_operator(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        return left is right

    def visit_type(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        return left._compare_type_affinity(right)

    def visit_plain_dict(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        return left == right

    def visit_dialect_options(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        return left == right

    def visit_annotations_key(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        if left and right:
            return (
                left_parent._annotations_cache_key
                == right_parent._annotations_cache_key
            )
        else:
            return left == right

    def visit_with_context_options(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        return tuple((fn.__code__, c_key) for fn, c_key in left) == tuple(
            (fn.__code__, c_key) for fn, c_key in right
        )

    def visit_plain_obj(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        return left == right

    def visit_named_ddl_element(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        if left is None:
            if right is not None:
                return COMPARE_FAILED

        return left.name == right.name

    def visit_prefix_sequence(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        for (l_clause, l_str), (r_clause, r_str) in zip_longest(
            left, right, fillvalue=(None, None)
        ):
            if l_str != r_str:
                return COMPARE_FAILED
            else:
                self.stack.append((l_clause, r_clause))

    def visit_setup_join_tuple(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        # TODO: look at attrname for "legacy_join" and use different structure
        for (
            (l_target, l_onclause, l_from, l_flags),
            (r_target, r_onclause, r_from, r_flags),
        ) in zip_longest(left, right, fillvalue=(None, None, None, None)):
            if l_flags != r_flags:
                return COMPARE_FAILED
            self.stack.append((l_target, r_target))
            self.stack.append((l_onclause, r_onclause))
            self.stack.append((l_from, r_from))

    def visit_memoized_select_entities(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        return self.visit_clauseelement_tuple(
            attrname, left_parent, left, right_parent, right, **kw
        )

    def visit_table_hint_list(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        left_keys = sorted(left, key=lambda elem: (elem[0].fullname, elem[1]))
        right_keys = sorted(
            right, key=lambda elem: (elem[0].fullname, elem[1])
        )
        for (ltable, ldialect), (rtable, rdialect) in zip_longest(
            left_keys, right_keys, fillvalue=(None, None)
        ):
            if ldialect != rdialect:
                return COMPARE_FAILED
            elif left[(ltable, ldialect)] != right[(rtable, rdialect)]:
                return COMPARE_FAILED
            else:
                self.stack.append((ltable, rtable))

    def visit_statement_hint_list(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        return left == right

    def visit_unknown_structure(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        raise NotImplementedError()

    def visit_dml_ordered_values(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        # sequence of tuple pairs

        for (lk, lv), (rk, rv) in zip_longest(
            left, right, fillvalue=(None, None)
        ):
            if not self._compare_dml_values_or_ce(lk, rk, **kw):
                return COMPARE_FAILED

    def _compare_dml_values_or_ce(self, lv, rv, **kw):
        lvce = hasattr(lv, "__clause_element__")
        rvce = hasattr(rv, "__clause_element__")
        if lvce != rvce:
            return False
        elif lvce and not self.compare_inner(lv, rv, **kw):
            return False
        elif not lvce and lv != rv:
            return False
        elif not self.compare_inner(lv, rv, **kw):
            return False

        return True

    def visit_dml_values(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        if left is None or right is None or len(left) != len(right):
            return COMPARE_FAILED

        if isinstance(left, collections_abc.Sequence):
            for lv, rv in zip(left, right):
                if not self._compare_dml_values_or_ce(lv, rv, **kw):
                    return COMPARE_FAILED
        elif isinstance(right, collections_abc.Sequence):
            return COMPARE_FAILED
        else:
            # dictionaries guaranteed to support insert ordering in
            # py37 so that we can compare the keys in order.  without
            # this, we can't compare SQL expression keys because we don't
            # know which key is which
            for (lk, lv), (rk, rv) in zip(left.items(), right.items()):
                if not self._compare_dml_values_or_ce(lk, rk, **kw):
                    return COMPARE_FAILED
                if not self._compare_dml_values_or_ce(lv, rv, **kw):
                    return COMPARE_FAILED

    def visit_dml_multi_values(
        self, attrname, left_parent, left, right_parent, right, **kw
    ):
        for lseq, rseq in zip_longest(left, right, fillvalue=None):
            if lseq is None or rseq is None:
                return COMPARE_FAILED

            for ld, rd in zip_longest(lseq, rseq, fillvalue=None):
                if (
                    self.visit_dml_values(
                        attrname, left_parent, ld, right_parent, rd, **kw
                    )
                    is COMPARE_FAILED
                ):
                    return COMPARE_FAILED

    def compare_expression_clauselist(self, left, right, **kw):
        if left.operator is right.operator:
            if operators.is_associative(left.operator):
                if self._compare_unordered_sequences(
                    left.clauses, right.clauses, **kw
                ):
                    return ["operator", "clauses"]
                else:
                    return COMPARE_FAILED
            else:
                return ["operator"]
        else:
            return COMPARE_FAILED

    def compare_clauselist(self, left, right, **kw):
        return self.compare_expression_clauselist(left, right, **kw)

    def compare_binary(self, left, right, **kw):
        if left.operator == right.operator:
            if operators.is_commutative(left.operator):
                if (
                    self.compare_inner(left.left, right.left, **kw)
                    and self.compare_inner(left.right, right.right, **kw)
                ) or (
                    self.compare_inner(left.left, right.right, **kw)
                    and self.compare_inner(left.right, right.left, **kw)
                ):
                    return ["operator", "negate", "left", "right"]
                else:
                    return COMPARE_FAILED
            else:
                return ["operator", "negate"]
        else:
            return COMPARE_FAILED

    def compare_bindparam(self, left, right, **kw):
        compare_keys = kw.pop("compare_keys", True)
        compare_values = kw.pop("compare_values", True)

        if compare_values:
            omit = []
        else:
            # this means, "skip these, we already compared"
            omit = ["callable", "value"]

        if not compare_keys:
            omit.append("key")

        return omit


class ColIdentityComparatorStrategy(TraversalComparatorStrategy):
    def compare_column_element(
        self, left, right, use_proxies=True, equivalents=(), **kw
    ):
        """Compare ColumnElements using proxies and equivalent collections.

        This is a comparison strategy specific to the ORM.
        """

        to_compare = (right,)
        if equivalents and right in equivalents:
            to_compare = equivalents[right].union(to_compare)

        for oth in to_compare:
            if use_proxies and left.shares_lineage(oth):
                return SKIP_TRAVERSE
            elif hash(left) == hash(right):
                return SKIP_TRAVERSE
        else:
            return COMPARE_FAILED

    def compare_column(self, left, right, **kw):
        return self.compare_column_element(left, right, **kw)

    def compare_label(self, left, right, **kw):
        return self.compare_column_element(left, right, **kw)

    def compare_table(self, left, right, **kw):
        # tables compare on identity, since it's not really feasible to
        # compare them column by column with the above rules
        return SKIP_TRAVERSE if left is right else COMPARE_FAILED
