unnesting buffer building

Author: rok

cpp/src/parquet/file_reader.cc

@@ -441,6 +441,7 @@ class SerializedFile : public ParquetFileReader::Contents {
     PARQUET_ASSIGN_OR_THROW(
         auto footer_buffer,
         source_->ReadAt(source_size_ - footer_read_size, footer_read_size));
+    uint32_t metadata_len = ParseFooterLength(footer_buffer, footer_read_size);
     if (properties_.read_flatbuffer_metadata_if_present()) {
       // Try to extract flatbuffer metadata from footer
       std::string flatbuffer_data;
@@ -463,14 +464,13 @@ class SerializedFile : public ParquetFileReader::Contents {
           auto thrift_metadata =
               std::make_unique<format::FileMetaData>(FromFlatbuffer(fb_metadata));
           file_metadata_ =
-              FileMetaData::Make(std::move(thrift_metadata), *result, properties_);
+              FileMetaData::Make(std::move(thrift_metadata), metadata_len, properties_);
           return;
         }
       }
       // If extraction failed or returned 0 (no flatbuffer), fall through to standard
       // parsing
     }
-    uint32_t metadata_len = ParseFooterLength(footer_buffer, footer_read_size);
     int64_t metadata_start = source_size_ - kFooterSize - metadata_len;
 
     std::shared_ptr<::arrow::Buffer> metadata_buffer;

cpp/src/parquet/metadata3.cc

@@ -981,6 +981,14 @@ struct FlatbufferConverter {
     std::optional<decltype(To(cm.statistics, rg_idx, col_idx))> statistics;
     if (cm.__isset.statistics) statistics = To(cm.statistics, rg_idx, col_idx);
 
+    // Create sub-objects before starting the builder (FlatBuffers requirement).
+    flatbuffers::Offset<format3::BloomFilterInfo> bloom_filter;
+    if (cm.__isset.bloom_filter_offset) {
+      bloom_filter = format3::CreateBloomFilterInfo(
+          root, cm.bloom_filter_offset,
+          cm.__isset.bloom_filter_length ? cm.bloom_filter_length : 0);
+    }
+
     // All offsets are relative to the row group.
     const auto& rg = md.row_groups[rg_idx];
 
@@ -1000,9 +1008,6 @@ struct FlatbufferConverter {
     if (statistics) b.add_statistics(*statistics);
     b.add_is_fully_dict_encoded(To(cm));
     if (cm.__isset.bloom_filter_offset) {
-      auto bloom_filter = format3::CreateBloomFilterInfo(
-          root, cm.bloom_filter_offset,
-          cm.__isset.bloom_filter_length ? cm.bloom_filter_length : 0);
       b.add_bloom_filter(bloom_filter);
     }