diff --git a/packages/kestrel_core/src/kestrel/frontend/completor.py b/packages/kestrel_core/src/kestrel/frontend/completor.py
index 019c6f45..6a2791b7 100644
--- a/packages/kestrel_core/src/kestrel/frontend/completor.py
+++ b/packages/kestrel_core/src/kestrel/frontend/completor.py
@@ -132,24 +132,27 @@ def do_complete(
 
         # handle optional components
         if ast:
-            stmt = ast.children[-1].children[0]
-            cmd = (
-                stmt.children[1].data.value
-                if stmt.data.value == "assignment"
-                else stmt.data.value
-            )
-            if cmd == "disp":
-                for clause in ("attr_clause", "limit_clause", "offset_clause"):
-                    if not list(stmt.find_data(clause)):
-                        suggestions.append("ATTR")
-            elif cmd in ("expression", "find") and not list(
-                stmt.find_data("where_clause")
-            ):
-                suggestions.append("WHERE")
-            elif cmd in ("get", "find") and not list(stmt.find_data("timerange")):
-                suggestions.append("START")
-            elif cmd == "apply" and not list(stmt.find_data("args")):
-                suggestions.append("WITH")
+            if ast.children:
+                stmt = ast.children[-1].children[0]
+                cmd = (
+                    stmt.children[1].data.value
+                    if stmt.data.value == "assignment"
+                    else stmt.data.value
+                )
+                if cmd == "disp":
+                    for clause in ("attr_clause", "limit_clause", "offset_clause"):
+                        if not list(stmt.find_data(clause)):
+                            suggestions.append("ATTR")
+                elif cmd in ("expression", "find") and not list(
+                    stmt.find_data("where_clause")
+                ):
+                    suggestions.append("WHERE")
+                elif cmd in ("get", "find") and not list(stmt.find_data("timerange")):
+                    suggestions.append("START")
+                elif cmd == "apply" and not list(stmt.find_data("args")):
+                    suggestions.append("WITH")
+            else:
+                suggestions = ["DISP", "APPLY", "EXPLAIN", "INFO", "SAVE", "DESCRIBE"]
 
         suggestions = [x for x in set(suggestions) if x]
         _p = last_word_prefix
diff --git a/packages/kestrel_core/src/kestrel/interface/codegen/sql.py b/packages/kestrel_core/src/kestrel/interface/codegen/sql.py
index 349224bf..f703dfef 100644
--- a/packages/kestrel_core/src/kestrel/interface/codegen/sql.py
+++ b/packages/kestrel_core/src/kestrel/interface/codegen/sql.py
@@ -133,7 +133,7 @@ def __init__(
 
     @typechecked
     def _map_identifier_field(self, field) -> ColumnElement:
-        if self.data_mapping and not self.is_subquery:
+        if self.data_mapping:
             comps = translate_comparison_to_native(self.data_mapping, field, "", None)
             if len(comps) > 1:
                 raise InvalidMappingWithMultipleIdentifierFields(comps)
@@ -155,10 +155,15 @@ def _render_comp(self, comp: FBasicComparison) -> BinaryExpression:
                     *[self._map_identifier_field(field) for field in comp.fields]
                 )
             rendered_comp = comp2func[comp.op](col, comp.value)
-        elif self.data_mapping and not self.is_subquery:  # translation needed
+        elif self.data_mapping:
             comps = translate_comparison_to_native(
                 self.data_mapping, comp.field, comp.op, comp.value
             )
+            if self.is_subquery:
+                # do not translate field
+                # only translate value
+                comps = [(comp.field, op, value) for (_, op, value) in comps]
+
             translated_comps = (
                 (
                     ~comp2func[op](column(field), value)
diff --git a/packages/kestrel_core/src/kestrel/mapping/data_model.py b/packages/kestrel_core/src/kestrel/mapping/data_model.py
index a61755fe..f45c3f9c 100644
--- a/packages/kestrel_core/src/kestrel/mapping/data_model.py
+++ b/packages/kestrel_core/src/kestrel/mapping/data_model.py
@@ -447,7 +447,18 @@ def translate_dataframe(df: DataFrame, to_native_nested_map: dict) -> DataFrame:
                     transformer_name = transformer_names.pop()
                     if isinstance(transformer_name, dict):
                         # Not actually a named function; it's a literal value map
-                        df[col] = df[col].replace(transformer_name)
+                        value_map = {}
+                        for k, vl in transformer_name.items():
+                            if len(vl) > 1:
+                                raise NotImplementedError(
+                                    "Multiple to OCSF value mapping"
+                                )
+                            else:
+                                value_map[k] = vl[0]
+                        # use .apply intead of .replace to handle type correctly
+                        df[col] = df[col].apply(
+                            lambda x: value_map[x] if x in value_map else x
+                        )
                     else:
                         s = run_transformer_on_series(
                             transformer_name, df[col].dropna()