feat: Track size for ParquetMetadata (#5)

Author: cristipp

parquet/src/file/footer.rs

@@ -117,7 +117,11 @@ pub fn parse_metadata<R: ChunkReader>(chunk_reader: &R) -> Result<ParquetMetaDat
         schema_descr,
         column_orders,
     );
-    Ok(ParquetMetaData::new(file_metadata, row_groups))
+    Ok(ParquetMetaData::new_with_size(
+        file_metadata,
+        row_groups,
+        footer_metadata_len as u32,
+    ))
 }
 
 /// Parses column orders from Thrift definition.

parquet/src/file/metadata.rs

@@ -50,15 +50,26 @@ use crate::schema::types::{
 pub struct ParquetMetaData {
     file_metadata: FileMetaData,
     row_groups: Vec<RowGroupMetaData>,
+    /// Size of serialized metadata. See footer::parse_metadata
+    metadata_size: u32,
 }
 
 impl ParquetMetaData {
     /// Creates Parquet metadata from file metadata and a list of row group metadata `Arc`s
     /// for each available row group.
     pub fn new(file_metadata: FileMetaData, row_groups: Vec<RowGroupMetaData>) -> Self {
+        ParquetMetaData::new_with_size(file_metadata, row_groups, 0)
+    }
+
+    pub fn new_with_size(
+        file_metadata: FileMetaData,
+        row_groups: Vec<RowGroupMetaData>,
+        metadata_size: u32,
+    ) -> Self {
         ParquetMetaData {
             file_metadata,
             row_groups,
+            metadata_size,
         }
     }
 
@@ -72,6 +83,10 @@ impl ParquetMetaData {
         self.row_groups.len()
     }
 
+    pub fn metadata_size(&self) -> u32 {
+        self.metadata_size
+    }
+
     /// Returns row group metadata for `i`th position.
     /// Position should be less than number of row groups `num_row_groups`.
     pub fn row_group(&self, i: usize) -> &RowGroupMetaData {

parquet/src/file/serialized_reader.rs

@@ -158,9 +158,10 @@ impl<R: 'static + ChunkReader> SerializedFileReader<R> {
                 filtered_row_groups.push(row_group_metadata.clone());
             }
         }
-        self.metadata = ParquetMetaData::new(
+        self.metadata = ParquetMetaData::new_with_size(
             self.metadata.file_metadata().clone(),
             filtered_row_groups,
+            self.metadata.metadata_size(),
         );
     }
 }