revert: chore(ir): tie the uniqueness of a self reference to its parent

This reverts commit 03d08d2.

ibis/backends/base/sqlglot/compiler.py

@@ -873,7 +873,7 @@ def visit_DatabaseTable(self, op, *, name, namespace, schema, source):
         )
 
     @visit_node.register(ops.SelfReference)
-    def visit_SelfReference(self, op, *, parent):
+    def visit_SelfReference(self, op, *, parent, identifier):
         return parent.as_(op.name, quoted=self.quoted)
 
     @visit_node.register(ops.JoinChain)

ibis/expr/operations/relations.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import itertools
 import typing
 from abc import abstractmethod
 from typing import TYPE_CHECKING, Annotated, Any, Literal, Optional
@@ -261,11 +262,15 @@ def schema(self):
 
 @public
 class SelfReference(Relation):
+    _uid_counter = itertools.count()
+
     parent: Relation
+    identifier: Optional[int] = None
 
-    @attribute
-    def identifier(self):
-        return hash(self.parent)
+    def __init__(self, parent, identifier):
+        if identifier is None:
+            identifier = next(self._uid_counter)
+        super().__init__(parent=parent, identifier=identifier)
 
     @attribute
     def name(self) -> str: