Add ParquetMetadataWriter allow ad-hoc encoding of ParquetMetadata

Author: adriangb

parquet/src/file/metadata/mod.rs

@@ -86,7 +86,7 @@ pub type ParquetOffsetIndex = Vec<Vec<OffsetIndexMetaData>>;
 ///
 /// [`parquet.thrift`]: https://github.com/apache/parquet-format/blob/master/src/main/thrift/parquet.thrift
 /// [`parse_metadata`]: crate::file::footer::parse_metadata
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub struct ParquetMetaData {
     /// File level metadata
     file_metadata: FileMetaData,
@@ -222,7 +222,7 @@ pub type FileMetaDataPtr = Arc<FileMetaData>;
 /// File level metadata for a Parquet file.
 ///
 /// Includes the version of the file, metadata, number of rows, schema, and column orders
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub struct FileMetaData {
     version: i32,
     num_rows: i64,

parquet/src/file/page_index/index.rs

@@ -168,6 +168,38 @@ impl<T: ParquetValueType> NativeIndex<T> {
             boundary_order: index.boundary_order,
         })
     }
+
+    pub(crate) fn to_thrift(&self) -> ColumnIndex {
+        let min_values = self
+            .indexes
+            .iter()
+            .map(|x| x.min_bytes().map(|x| x.to_vec()))
+            .collect::<Option<Vec<_>>>()
+            .unwrap_or_else(|| vec![vec![]; self.indexes.len()]);
+
+        let max_values = self
+            .indexes
+            .iter()
+            .map(|x| x.max_bytes().map(|x| x.to_vec()))
+            .collect::<Option<Vec<_>>>()
+            .unwrap_or_else(|| vec![vec![]; self.indexes.len()]);
+
+        let null_counts = self
+            .indexes
+            .iter()
+            .map(|x| x.null_count())
+            .collect::<Option<Vec<_>>>();
+
+        ColumnIndex::new(
+            self.indexes.iter().map(|x| x.min().is_none()).collect(),
+            min_values,
+            max_values,
+            self.boundary_order,
+            null_counts,
+            None,
+            None,
+        )
+    }
 }
 
 #[cfg(test)]