perf: dont query for impossible child/ancestor (#16577)

Also avoid manual plucking

frappe/utils/nestedset.py

@@ -352,34 +352,29 @@ def get_ancestors_of(doctype, name, order_by="lft desc", limit=None):
 	"""Get ancestor elements of a DocType with a tree structure"""
 	lft, rgt = frappe.db.get_value(doctype, name, ["lft", "rgt"])
 
-	result = [
-		d["name"]
-		for d in frappe.db.get_all(
-			doctype,
-			{"lft": ["<", lft], "rgt": [">", rgt]},
-			"name",
-			order_by=order_by,
-			limit_page_length=limit,
-		)
-	]
-
-	return result or []
+	return frappe.get_all(
+		doctype,
+		{"lft": ["<", lft], "rgt": [">", rgt]},
+		"name",
+		order_by=order_by,
+		limit_page_length=limit,
+		pluck="name",
+	)
 
 
 def get_descendants_of(doctype, name, order_by="lft desc", limit=None, ignore_permissions=False):
 	"""Return descendants of the current record"""
 	lft, rgt = frappe.db.get_value(doctype, name, ["lft", "rgt"])
 
-	result = [
-		d["name"]
-		for d in frappe.db.get_list(
-			doctype,
-			{"lft": [">", lft], "rgt": ["<", rgt]},
-			"name",
-			order_by=order_by,
-			limit_page_length=limit,
-			ignore_permissions=ignore_permissions,
-		)
-	]
-
-	return result or []
+	if rgt - lft <= 1:
+		return []
+
+	return frappe.get_list(
+		doctype,
+		{"lft": [">", lft], "rgt": ["<", rgt]},
+		"name",
+		order_by=order_by,
+		limit_page_length=limit,
+		ignore_permissions=ignore_permissions,
+		pluck="name",
+	)