Initial handling of decorrelation setup

pydough/conversion/hybrid_tree.py

@@ -895,6 +895,7 @@ def __init__(
         self._is_connection_root: bool = is_connection_root
         self._agg_keys: list[HybridExpr] | None = None
         self._join_keys: list[tuple[HybridExpr, HybridExpr]] | None = None
+        self._correlated_children: set[int] = set()
         if isinstance(root_operation, HybridPartition):
             self._join_keys = []
 
@@ -935,6 +936,14 @@ def children(self) -> list[HybridConnection]:
         """
         return self._children
 
+    @property
+    def correlated_children(self) -> set[int]:
+        """
+        The set of indices of children that contain correlated references to
+        the current hybrid tree.
+        """
+        return self._correlated_children
+
     @property
     def successor(self) -> Optional["HybridTree"]:
         """
@@ -1634,6 +1643,8 @@ def make_hybrid_correl_expr(
                 collection, back_expr.term_name, remaining_steps_back
             )
             parent_result = self.make_hybrid_expr(parent_tree, new_expr, {}, False)
+        if not isinstance(parent_result, HybridCorrelExpr):
+            parent_tree.correlated_children.add(len(parent_tree.children))
         # Restore parent_tree back onto the stack, since evaluating `back_expr`
         # does not change the program's current placement in the sutbtrees.
         self.stack.append(parent_tree)

pydough/conversion/relational_converter.py

@@ -44,6 +44,7 @@
 )
 from pydough.types import BooleanType, Int64Type, UnknownType
 
+from .hybrid_decorrelater import decorrelate_hybrid
 from .hybrid_tree import (
     ConnectionType,
     HybridBackRefExpr,
@@ -996,10 +997,11 @@ def convert_ast_to_relational(
     final_terms: set[str] = node.calc_terms
     node = translator.preprocess_root(node)
 
-    # Convert the QDAG node to the hybrid form, then invoke the relational
-    # conversion procedure. The first element in the returned list is the
-    # final rel node.
+    # Convert the QDAG node to the hybrid form, decorrelate it, then invoke
+    # the relational conversion procedure. The first element in the returned
+    # list is the final rel node.
     hybrid: HybridTree = HybridTranslator(configs).make_hybrid_tree(node, None)
+    decorrelate_hybrid(hybrid)
     renamings: dict[str, str] = hybrid.pipeline[-1].renamings
     output: TranslationOutput = translator.rel_translation(
         None, hybrid, len(hybrid.pipeline) - 1