diff --git a/src/handlers/dashboard/get_chart_data.py b/src/handlers/dashboard/get_chart_data.py
index c98ea07..a68ba2b 100644
--- a/src/handlers/dashboard/get_chart_data.py
+++ b/src/handlers/dashboard/get_chart_data.py
@@ -17,7 +17,7 @@
 logger.setLevel(log_level)
 
 
-def _get_table_cols(dp_id: str, version: str | None = None) -> list:
+def _get_table_cols(dp_id: str) -> list:
     """Returns the columns associated with a table.
 
     Since running an athena query takes a decent amount of time due to queueing
@@ -26,11 +26,11 @@ def _get_table_cols(dp_id: str, version: str | None = None) -> list:
     """
 
     s3_bucket_name = os.environ.get("BUCKET_NAME")
-    dp_name = dp_id.rsplit("__", 1)[0]
-    prefix = f"{enums.BucketPath.CSVAGGREGATE.value}/{dp_id.split('__')[0]}/{dp_name}"
+    study, name, version = dp_id.split("__")
+    prefix = f"{enums.BucketPath.CSVAGGREGATE.value}/{study}/{study}__{name}"
     if version is None:
         version = functions.get_latest_data_package_version(s3_bucket_name, prefix)
-    s3_key = f"{prefix}/{version}/{dp_name}__aggregate.csv"
+    s3_key = f"{prefix}/{version}/{study}__{name}__aggregate.csv"
     s3_client = boto3.client("s3")
     try:
         s3_iter = s3_client.get_object(
@@ -98,14 +98,16 @@ def _format_payload(
     if "stratifier" in query_params.keys():
         payload["stratifier"] = query_params["stratifier"]
         counts = {}
-        for unique_val in df[query_params["column"]]:
-            df_slice = df[df[query_params["column"]] == unique_val]
+        for unique_val in df[query_params["column"]].unique():
+            column_mask = df[query_params["column"]] == unique_val
+            df_slice = df[column_mask]
             df_slice = df_slice.drop(columns=[query_params["stratifier"], query_params["column"]])
             counts[unique_val] = int(df_slice[count_col].sum())
         payload["counts"] = counts
         data = []
         for unique_strat in df[query_params["stratifier"]].unique():
-            df_slice = df[df[query_params["stratifier"]] == unique_strat]
+            strat_mask = df[query_params["stratifier"]] == unique_strat
+            df_slice = df[strat_mask]
             df_slice = df_slice.drop(columns=[query_params["stratifier"]])
             rows = df_slice.values.tolist()
             data.append({"stratifier": unique_strat, "rows": rows})
diff --git a/tests/dashboard/test_get_chart_data.py b/tests/dashboard/test_get_chart_data.py
index c69314c..0f6c9c5 100644
--- a/tests/dashboard/test_get_chart_data.py
+++ b/tests/dashboard/test_get_chart_data.py
@@ -102,8 +102,6 @@ def test_build_query(query_params, filters, path_params, query_str):
 def test_format_payload(query_params, filters, expected_payload):
     df = mock_data_frame(filters)
     payload = get_chart_data._format_payload(df, query_params, filters, "cnt")
-    print(query_params)
-    print(payload)
     assert payload == expected_payload
 
 
@@ -120,7 +118,7 @@ def test_get_data_cols(mock_bucket):
         (
             "SELECT gender, sum(cnt) as cnt"
             f'FROM "{TEST_GLUE_DB}"."test_study" '
-            "WHERE COALESCE (race) IS NOT Null AND gender IS NOT Null "
+            "WHERE COALESCE (race) IS NOT NULL AND gender IS NOT NULL "
             "AND gender LIKE 'female' "
             "GROUP BY gender",
             "cnt",