diff --git a/src/parquet.rs b/src/parquet.rs
index 30ec259..8dcfc40 100644
--- a/src/parquet.rs
+++ b/src/parquet.rs
@@ -14,7 +14,7 @@ pub struct MetricRequest {
 fn get_metrics_from_file(
     file_url: &String,
     columns: &[String],
-    geo_ids: Option<&[String]>,
+    geo_ids: Option<&[&str]>,
 ) -> Result<DataFrame> {
     let mut cols: Vec<Expr> = columns.iter().map(|c| col(c)).collect();
     cols.push(col(GEO_ID_COL_NAME));
@@ -39,7 +39,7 @@ fn get_metrics_from_file(
 /// Given a set of metrics and optional geo_ids, this function will
 /// retrive all the required metrics from the cloud blob storage
 ///
-pub fn get_metrics(metrics: &[MetricRequest], geo_ids: Option<&[String]>) -> Result<DataFrame> {
+pub fn get_metrics(metrics: &[MetricRequest], geo_ids: Option<&[&str]>) -> Result<DataFrame> {
     let file_list: HashSet<String> = metrics.iter().map(|m| m.file.clone()).collect();
 
     let dfs: Result<Vec<DataFrame>> = file_list
@@ -59,22 +59,22 @@ pub fn get_metrics(metrics: &[MetricRequest], geo_ids: Option<&[String]>) -> Res
         })
         .collect();
 
-    let joined_df = dfs?.iter().fold(None, |acc, df| match acc {
-        None => Some(df.clone()),
-        Some(acc_df) => Some(
-            // This unwrap should be ok because we would expect the
-            // previous calls to fail if "GEOID" is not present in
-            // it's columns
-            acc_df
-                .join(
-                    df,
-                    vec![GEO_ID_COL_NAME],
-                    vec![GEO_ID_COL_NAME],
-                    JoinArgs::new(JoinType::Inner),
-                )
-                .unwrap(),
-        ),
-    });
+    let mut joined_df: Option<DataFrame> = None;
+
+    // Merge the dataframes from each remove file in to a single
+    // dataframe
+    for df in dfs? {
+        if let Some(prev_dfs) = joined_df {
+            joined_df = Some(prev_dfs.join(
+                &df,
+                vec![GEO_ID_COL_NAME],
+                vec![GEO_ID_COL_NAME],
+                JoinArgs::new(JoinType::Inner),
+            )?);
+        } else {
+            joined_df = Some(df.clone());
+        }
+    }
 
     joined_df.with_context(|| "Failed to combine data queries")
 }
@@ -91,7 +91,6 @@ mod tests {
                 column:"B17021_E006".into() 
             }];
         let df = get_metrics(&metrics, None);
-        println!("{df:#?}");
         assert!(df.is_ok(), "We should get back a result");
         let df = df.unwrap();
         assert_eq!(
@@ -123,10 +122,9 @@ mod tests {
             }];
         let df = get_metrics(
             &metrics,
-            Some(&["1400000US01001020100".into(), "1400000US01001020300".into()]),
+            Some(&["1400000US01001020100", "1400000US01001020300"]),
         );
 
-        println!("{df:#?}");
         assert!(df.is_ok(), "We should get back a result");
         let df = df.unwrap();
         assert_eq!(