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traversals.py
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# sql/traversals.py # Copyright (C) 2005-2024 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 . 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 from ..util.typing import Self 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() _copy_internals.generate_dispatch( cls, cls._traverse_internals, "_generated_copy_internals_traversal", ) _get_children.generate_dispatch( cls, cls._traverse_internals, "_generated_get_children_traversal", ) 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, other: Self) -> 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, internal_dispatch: _TraverseInternalsType, method_name: str, ) -> Callable[[Self, Self], 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, internal_dispatch: _TraverseInternalsType, method_name: str, ) -> Callable[[Self], 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, internal_dispatch: _TraverseInternalsType, method_name: str, ) -> Callable[[Self, 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, other: Self) -> None: cls = self.__class__ shallow_copy: Callable[[Self, Self], 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, **kw: Any) -> Self: """Create a shallow copy""" c = self.__class__.__new__(self.__class__) self._shallow_copy_to(c) return c class GenerativeOnTraversal(HasShallowCopy): """Supplies Generative behavior but making use of traversals to shallow copy. .. seealso:: :class:`sqlalchemy.sql.base.Generative` """ __slots__ = () def _generate(self) -> Self: 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 elif right_child is None: return False 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 == 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