perf(reader): Add Parquet metadata size hint option to ArrowReaderBuilder (#2173)

## Which issue does this PR close?


- Partially address #2172.

## What changes are included in this PR?

Add `with_metadata_size_hint` to `ArrowReaderBuilder`, allowing callers
to configure the number of bytes to prefetch when reading Parquet footer
metadata. No default is set—callers opt in via the builder. When unset,
behavior is unchanged.

## Are these changes tested?

Existing tests.

Author: mbutrovich

crates/iceberg/src/arrow/delete_file_loader.rs

@@ -64,6 +64,7 @@ impl BasicDeleteFileLoader {
             self.file_io.clone(),
             false,
             None,
+            None,
         )
         .await?
         .build()?

crates/iceberg/src/arrow/reader.rs

@@ -67,6 +67,7 @@ pub struct ArrowReaderBuilder {
     concurrency_limit_data_files: usize,
     row_group_filtering_enabled: bool,
     row_selection_enabled: bool,
+    metadata_size_hint: Option<usize>,
 }
 
 impl ArrowReaderBuilder {
@@ -80,6 +81,7 @@ impl ArrowReaderBuilder {
             concurrency_limit_data_files: num_cpus,
             row_group_filtering_enabled: true,
             row_selection_enabled: false,
+            metadata_size_hint: None,
         }
     }
 
@@ -108,6 +110,15 @@ impl ArrowReaderBuilder {
         self
     }
 
+    /// Provide a hint as to the number of bytes to prefetch for parsing the Parquet metadata
+    ///
+    /// This hint can help reduce the number of fetch requests. For more details see the
+    /// [ParquetMetaDataReader documentation](https://docs.rs/parquet/latest/parquet/file/metadata/struct.ParquetMetaDataReader.html#method.with_prefetch_hint).
+    pub fn with_metadata_size_hint(mut self, metadata_size_hint: usize) -> Self {
+        self.metadata_size_hint = Some(metadata_size_hint);
+        self
+    }
+
     /// Build the ArrowReader.
     pub fn build(self) -> ArrowReader {
         ArrowReader {
@@ -120,6 +131,7 @@ impl ArrowReaderBuilder {
             concurrency_limit_data_files: self.concurrency_limit_data_files,
             row_group_filtering_enabled: self.row_group_filtering_enabled,
             row_selection_enabled: self.row_selection_enabled,
+            metadata_size_hint: self.metadata_size_hint,
         }
     }
 }
@@ -136,6 +148,7 @@ pub struct ArrowReader {
 
     row_group_filtering_enabled: bool,
     row_selection_enabled: bool,
+    metadata_size_hint: Option<usize>,
 }
 
 impl ArrowReader {
@@ -147,6 +160,7 @@ impl ArrowReader {
         let concurrency_limit_data_files = self.concurrency_limit_data_files;
         let row_group_filtering_enabled = self.row_group_filtering_enabled;
         let row_selection_enabled = self.row_selection_enabled;
+        let metadata_size_hint = self.metadata_size_hint;
 
         // Fast-path for single concurrency to avoid overhead of try_flatten_unordered
         let stream: ArrowRecordBatchStream = if concurrency_limit_data_files == 1 {
@@ -162,6 +176,7 @@ impl ArrowReader {
                             self.delete_file_loader.clone(),
                             row_group_filtering_enabled,
                             row_selection_enabled,
+                            metadata_size_hint,
                         )
                     })
                     .map_err(|err| {
@@ -183,6 +198,7 @@ impl ArrowReader {
                             self.delete_file_loader.clone(),
                             row_group_filtering_enabled,
                             row_selection_enabled,
+                            metadata_size_hint,
                         )
                     })
                     .map_err(|err| {
@@ -205,6 +221,7 @@ impl ArrowReader {
         delete_file_loader: CachingDeleteFileLoader,
         row_group_filtering_enabled: bool,
         row_selection_enabled: bool,
+        metadata_size_hint: Option<usize>,
     ) -> Result<ArrowRecordBatchStream> {
         let should_load_page_index =
             (row_selection_enabled && task.predicate.is_some()) || !task.deletes.is_empty();
@@ -219,6 +236,7 @@ impl ArrowReader {
             file_io.clone(),
             should_load_page_index,
             None,
+            metadata_size_hint,
         )
         .await?;
 
@@ -271,6 +289,7 @@ impl ArrowReader {
                 file_io.clone(),
                 should_load_page_index,
                 Some(options),
+                metadata_size_hint,
             )
             .await?
         } else {
@@ -474,17 +493,22 @@ impl ArrowReader {
         file_io: FileIO,
         should_load_page_index: bool,
         arrow_reader_options: Option<ArrowReaderOptions>,
+        metadata_size_hint: Option<usize>,
     ) -> Result<ParquetRecordBatchStreamBuilder<ArrowFileReader>> {
         // Get the metadata for the Parquet file we need to read and build
         // a reader for the data within
         let parquet_file = file_io.new_input(data_file_path)?;
         let (parquet_metadata, parquet_reader) =
             try_join!(parquet_file.metadata(), parquet_file.reader())?;
-        let parquet_file_reader = ArrowFileReader::new(parquet_metadata, parquet_reader)
+        let mut parquet_file_reader = ArrowFileReader::new(parquet_metadata, parquet_reader)
             .with_preload_column_index(true)
             .with_preload_offset_index(true)
             .with_preload_page_index(should_load_page_index);
 
+        if let Some(hint) = metadata_size_hint {
+            parquet_file_reader = parquet_file_reader.with_metadata_size_hint(hint);
+        }
+
         // Create the record batch stream builder, which wraps the parquet file reader
         let options = arrow_reader_options.unwrap_or_default();
         let record_batch_stream_builder =