Revert "refactor: enhance expression handling by introducing _to_raw_expr function and updating _ensure_expr"

This reverts commit af3f475987a2fe089b31a4cc90483b660dc087f7.

Author: kosiew

python/datafusion/dataframe.py

@@ -44,7 +44,6 @@
     EXPR_TYPE_ERROR,
     Expr,
     SortKey,
-    _to_raw_expr,
     expr_list_to_raw_expr_list,
     sort_list_to_raw_sort_list,
 )
@@ -293,19 +292,21 @@ def __init__(
         self.bloom_filter_ndv = bloom_filter_ndv
 
 
-def _ensure_expr(value: Expr | str) -> expr_internal.Expr:
+def _ensure_expr(value: Expr) -> expr_internal.Expr:
     """Return the internal expression or raise ``TypeError`` if invalid.
 
     Args:
-        value: Candidate expression or column name.
+        value: Candidate expression.
 
     Returns:
         The internal expression representation.
 
     Raises:
-        TypeError: If ``value`` is not an instance of :class:`Expr` or ``str``.
+        TypeError: If ``value`` is not an instance of :class:`Expr`.
     """
-    return _to_raw_expr(value)
+    if not isinstance(value, Expr):
+        raise TypeError(EXPR_TYPE_ERROR)
+    return value.expr
 
 
 class DataFrame:

python/datafusion/expr.py

@@ -222,29 +222,6 @@
 ]
 
 
-def _to_raw_expr(value: Expr | str) -> expr_internal.Expr:
-    """Convert a Python expression or column name to its raw variant.
-
-    Args:
-        value: Candidate expression or column name.
-
-    Returns:
-        The internal :class:`~datafusion._internal.expr.Expr` representation.
-
-    Raises:
-        TypeError: If ``value`` is neither an :class:`Expr` nor ``str``.
-    """
-    if isinstance(value, str):
-        return Expr.column(value).expr
-    if isinstance(value, Expr):
-        return value.expr
-    error = (
-        "Expected Expr or column name, found:"
-        f" {type(value).__name__}. {EXPR_TYPE_ERROR}."
-    )
-    raise TypeError(error)
-
-
 def expr_list_to_raw_expr_list(
     expr_list: Optional[Sequence[Expr | str] | Expr | str],
 ) -> Optional[list[expr_internal.Expr]]:
@@ -253,11 +230,23 @@ def expr_list_to_raw_expr_list(
         expr_list = [expr_list]
     if expr_list is None:
         return None
-    return [_to_raw_expr(e) for e in expr_list]
+    raw_exprs: list[expr_internal.Expr] = []
+    for e in expr_list:
+        if isinstance(e, str):
+            raw_exprs.append(Expr.column(e).expr)
+        elif isinstance(e, Expr):
+            raw_exprs.append(e.expr)
+        else:
+            error = (
+                "Expected Expr or column name, found:"
+                f" {type(e).__name__}. {EXPR_TYPE_ERROR}."
+            )
+            raise TypeError(error)
+    return raw_exprs
 
 
 def sort_or_default(e: Expr | SortExpr) -> expr_internal.SortExpr:
-    """Return a :class:`SortExpr`, defaulting attributes when necessary."""
+    """Helper function to return a default Sort if an Expr is provided."""
     if isinstance(e, SortExpr):
         return e.raw_sort
     return SortExpr(e, ascending=True, nulls_first=True).raw_sort
@@ -273,11 +262,17 @@ def sort_list_to_raw_sort_list(
         return None
     raw_sort_list = []
     for item in sort_list:
-        if isinstance(item, SortExpr):
-            raw_sort_list.append(sort_or_default(item))
+        if isinstance(item, str):
+            expr_obj = Expr.column(item)
+        elif isinstance(item, (Expr, SortExpr)):
+            expr_obj = item
         else:
-            raw_expr = _to_raw_expr(item)  # may raise ``TypeError``
-            raw_sort_list.append(sort_or_default(Expr(raw_expr)))
+            error = (
+                "Expected Expr or column name, found:"
+                f" {type(item).__name__}. {EXPR_TYPE_ERROR}."
+            )
+            raise TypeError(error)
+        raw_sort_list.append(sort_or_default(expr_obj))
     return raw_sort_list