Add parquet_column_index and arrow_field accessors + test

parquet/src/arrow/arrow_reader/statistics.rs

@@ -1064,12 +1064,25 @@ where
 #[derive(Debug)]
 pub struct StatisticsConverter<'a> {
     /// the index of the matched column in the parquet schema
-    parquet_index: Option<usize>,
+    parquet_column_index: Option<usize>,
     /// The field (with data type) of the column in the arrow schema
     arrow_field: &'a Field,
 }
 
 impl<'a> StatisticsConverter<'a> {
+    /// Return the index of the column in the parquet schema, if any
+    ///
+    /// Returns `None` if the column is was present in the Arrow schema, but not
+    /// present in the parquet file
+    pub fn parquet_column_index(&self) -> Option<usize> {
+        self.parquet_column_index
+    }
+
+    /// Return the arrow schema's [`Field]` of the column in the arrow schema
+    pub fn arrow_field(&self) -> &'a Field {
+        self.arrow_field
+    }
+
     /// Returns a [`UInt64Array`] with row counts for each row group
     ///
     /// # Return Value
@@ -1102,7 +1115,7 @@ impl<'a> StatisticsConverter<'a> {
     where
         I: IntoIterator<Item = &'a RowGroupMetaData>,
     {
-        let Some(_) = self.parquet_index else {
+        let Some(_) = self.parquet_column_index else {
             return Ok(None);
         };
 
@@ -1159,7 +1172,7 @@ impl<'a> StatisticsConverter<'a> {
         };
 
         Ok(Self {
-            parquet_index,
+            parquet_column_index: parquet_index,
             arrow_field,
         })
     }
@@ -1210,7 +1223,7 @@ impl<'a> StatisticsConverter<'a> {
     {
         let data_type = self.arrow_field.data_type();
 
-        let Some(parquet_index) = self.parquet_index else {
+        let Some(parquet_index) = self.parquet_column_index else {
             return Ok(self.make_null_array(data_type, metadatas));
         };
 
@@ -1229,7 +1242,7 @@ impl<'a> StatisticsConverter<'a> {
     {
         let data_type = self.arrow_field.data_type();
 
-        let Some(parquet_index) = self.parquet_index else {
+        let Some(parquet_index) = self.parquet_column_index else {
             return Ok(self.make_null_array(data_type, metadatas));
         };
 
@@ -1246,7 +1259,7 @@ impl<'a> StatisticsConverter<'a> {
     where
         I: IntoIterator<Item = &'a RowGroupMetaData>,
     {
-        let Some(parquet_index) = self.parquet_index else {
+        let Some(parquet_index) = self.parquet_column_index else {
             let num_row_groups = metadatas.into_iter().count();
             return Ok(UInt64Array::from_iter(
                 std::iter::repeat(None).take(num_row_groups),
@@ -1322,7 +1335,7 @@ impl<'a> StatisticsConverter<'a> {
     {
         let data_type = self.arrow_field.data_type();
 
-        let Some(parquet_index) = self.parquet_index else {
+        let Some(parquet_index) = self.parquet_column_index else {
             return Ok(self.make_null_array(data_type, row_group_indices));
         };
 
@@ -1351,7 +1364,7 @@ impl<'a> StatisticsConverter<'a> {
     {
         let data_type = self.arrow_field.data_type();
 
-        let Some(parquet_index) = self.parquet_index else {
+        let Some(parquet_index) = self.parquet_column_index else {
             return Ok(self.make_null_array(data_type, row_group_indices));
         };
 
@@ -1378,7 +1391,7 @@ impl<'a> StatisticsConverter<'a> {
     where
         I: IntoIterator<Item = &'a usize>,
     {
-        let Some(parquet_index) = self.parquet_index else {
+        let Some(parquet_index) = self.parquet_column_index else {
             let num_row_groups = row_group_indices.into_iter().count();
             return Ok(UInt64Array::from_iter(
                 std::iter::repeat(None).take(num_row_groups),
@@ -1421,7 +1434,7 @@ impl<'a> StatisticsConverter<'a> {
     where
         I: IntoIterator<Item = &'a usize>,
     {
-        let Some(parquet_index) = self.parquet_index else {
+        let Some(parquet_index) = self.parquet_column_index else {
             // no matching column found in parquet_index;
             // thus we cannot extract page_locations in order to determine
             // the row count on a per DataPage basis.
@@ -2366,6 +2379,13 @@ mod test {
 
                 let converter =
                     StatisticsConverter::try_new(name, arrow_schema, parquet_schema).unwrap();
+
+                // test accessors on the converter
+                let parquet_column_index =
+                    parquet_column(parquet_schema, &arrow_schema, name).map(|(idx, _field)| idx);
+                assert_eq!(converter.parquet_column_index(), parquet_column_index);
+                assert_eq!(converter.arrow_field().name(), name);
+
                 let actual_min = converter.row_group_mins(row_groups.iter()).unwrap();
                 assert_eq!(&expected_min, &actual_min, "column {name}");