refactor: small tweak to allow use of dynamic fields in select rules

Author: stevenhsd

src/dve/core_engine/backends/implementations/duckdb/utilities.py

@@ -1,5 +1,6 @@
 """Utility objects for use with duckdb backend"""
 
+import itertools
 from dve.core_engine.backends.base.utilities import _split_multiexpr_string
 
 
@@ -24,7 +25,12 @@ def expr_mapping_to_columns(expressions: dict) -> list[str]:
 
 def expr_array_to_columns(expressions: list[str]) -> list[str]:
     """Create list of duckdb expressions from list of expressions"""
-    return [f"{expression}" for expression in expressions]
+    return list(
+        itertools.chain.from_iterable(
+            _split_multiexpr_string(expression) 
+            for expression in expressions
+            )
+        )
 
 
 def multiexpr_string_to_columns(expressions: str) -> list[str]: