GH-41579: [C++][Python][Parquet] Support reading/writing key-value metadata from/to ColumnChunkMetaData

cpp/src/parquet/column_writer.cc

@@ -40,6 +40,7 @@
 #include "arrow/util/crc32.h"
 #include "arrow/util/endian.h"
 #include "arrow/util/float16.h"
+#include "arrow/util/key_value_metadata.h"
 #include "arrow/util/logging.h"
 #include "arrow/util/rle_encoding_internal.h"
 #include "arrow/util/type_traits.h"
@@ -832,6 +833,9 @@ class ColumnWriterImpl {
   void FlushBufferedDataPages();
 
   ColumnChunkMetaDataBuilder* metadata_;
+  // key_value_metadata_ for the column chunk
+  // It would be nullptr if there is no KeyValueMetadata set.
+  std::shared_ptr<const KeyValueMetadata> key_value_metadata_;
   const ColumnDescriptor* descr_;
   // scratch buffer if validity bits need to be recalculated.
   std::shared_ptr<ResizableBuffer> bits_buffer_;
@@ -1100,6 +1104,7 @@ int64_t ColumnWriterImpl::Close() {
     if (rows_written_ > 0 && chunk_statistics.is_set()) {
       metadata_->SetStatistics(chunk_statistics);
     }
+    metadata_->SetKeyValueMetadata(key_value_metadata_);
     pager_->Close(has_dictionary_, fallback_);
   }
 
@@ -1397,6 +1402,25 @@ class TypedColumnWriterImpl : public ColumnWriterImpl, public TypedColumnWriter<
     return pages_change_on_record_boundaries_;
   }
 
+  void AddKeyValueMetadata(
+      const std::shared_ptr<const KeyValueMetadata>& key_value_metadata) override {
+    if (closed_) {
+      throw ParquetException("Cannot add key-value metadata to closed column");
+    }
+    if (key_value_metadata_ == nullptr) {
+      key_value_metadata_ = key_value_metadata;
+    } else if (key_value_metadata != nullptr) {
+      key_value_metadata_ = key_value_metadata_->Merge(*key_value_metadata);
+    }
+  }
+
+  void ResetKeyValueMetadata() override {
+    if (closed_) {
+      throw ParquetException("Cannot add key-value metadata to closed column");
+    }
+    key_value_metadata_ = nullptr;
+  }
+
  private:
   using ValueEncoderType = typename EncodingTraits<DType>::Encoder;
   using TypedStats = TypedStatistics<DType>;

cpp/src/parquet/column_writer.h

@@ -21,6 +21,7 @@
 #include <cstring>
 #include <memory>
 
+#include "arrow/type_fwd.h"
 #include "arrow/util/compression.h"
 #include "parquet/exception.h"
 #include "parquet/platform.h"
@@ -181,6 +182,17 @@ class PARQUET_EXPORT ColumnWriter {
   /// \brief The file-level writer properties
   virtual const WriterProperties* properties() = 0;
 
+  /// \brief Add key-value metadata to the ColumnChunk.
+  /// \param[in] key_value_metadata the metadata to add.
+  /// \note This will overwrite any existing metadata with the same key.
+  /// \throw ParquetException if Close() has been called.
+  virtual void AddKeyValueMetadata(
+      const std::shared_ptr<const ::arrow::KeyValueMetadata>& key_value_metadata) = 0;
+
+  /// \brief Reset the ColumnChunk key-value metadata.
+  /// \throw ParquetException if Close() has been called.
+  virtual void ResetKeyValueMetadata() = 0;
+
   /// \brief Write Apache Arrow columnar data directly to ColumnWriter. Returns
   /// error status if the array data type is not compatible with the concrete
   /// writer type.

cpp/src/parquet/column_writer_test.cc

@@ -23,10 +23,12 @@
 #include <gtest/gtest.h>
 
 #include "arrow/io/buffered.h"
+#include "arrow/io/file.h"
 #include "arrow/testing/gtest_util.h"
 #include "arrow/util/bit_util.h"
 #include "arrow/util/bitmap_builders.h"
 #include "arrow/util/config.h"
+#include "arrow/util/key_value_metadata.h"
 
 #include "parquet/column_page.h"
 #include "parquet/column_reader.h"
@@ -51,6 +53,9 @@ using schema::PrimitiveNode;
 
 namespace test {
 
+using ::testing::IsNull;
+using ::testing::NotNull;
+
 // The default size used in most tests.
 const int SMALL_SIZE = 100;
 #ifdef PARQUET_VALGRIND
@@ -385,6 +390,15 @@ class TestPrimitiveWriter : public PrimitiveTypedTest<TestType> {
     return metadata_accessor->encoding_stats();
   }
 
+  std::shared_ptr<const KeyValueMetadata> metadata_key_value_metadata() {
+    // Metadata accessor must be created lazily.
+    // This is because the ColumnChunkMetaData semantics dictate the metadata object is
+    // complete (no changes to the metadata buffer can be made after instantiation)
+    auto metadata_accessor =
+        ColumnChunkMetaData::Make(metadata_->contents(), this->descr_);
+    return metadata_accessor->key_value_metadata();
+  }
+
  protected:
   int64_t values_read_;
   // Keep the reader alive as for ByteArray the lifetime of the ByteArray
@@ -1705,5 +1719,55 @@ TEST(TestColumnWriter, WriteDataPageV2HeaderNullCount) {
   }
 }
 
+using TestInt32Writer = TestPrimitiveWriter<Int32Type>;
+
+TEST_F(TestInt32Writer, NoWriteKeyValueMetadata) {
+  auto writer = this->BuildWriter();
+  writer->Close();
+  auto key_value_metadata = metadata_key_value_metadata();
+  ASSERT_THAT(key_value_metadata, IsNull());
+}
+
+TEST_F(TestInt32Writer, WriteKeyValueMetadata) {
+  auto writer = this->BuildWriter();
+  writer->AddKeyValueMetadata(KeyValueMetadata::Make({"hello"}, {"world"}));
+  writer->Close();
+  auto key_value_metadata = metadata_key_value_metadata();
+  ASSERT_THAT(key_value_metadata, NotNull());
+  ASSERT_EQ(1, key_value_metadata->size());
+  ASSERT_OK_AND_ASSIGN(auto value, key_value_metadata->Get("hello"));
+  ASSERT_EQ("world", value);
+}
+
+TEST_F(TestInt32Writer, ResetKeyValueMetadata) {
+  auto writer = this->BuildWriter();
+  writer->AddKeyValueMetadata(KeyValueMetadata::Make({"hello"}, {"world"}));
+  writer->ResetKeyValueMetadata();
+  writer->Close();
+  auto key_value_metadata = metadata_key_value_metadata();
+  ASSERT_THAT(key_value_metadata, IsNull());
+}
+
+TEST_F(TestInt32Writer, WriteKeyValueMetadataEndToEnd) {
+  auto sink = CreateOutputStream();
+  {
+    auto file_writer = ParquetFileWriter::Open(
+        sink, std::dynamic_pointer_cast<schema::GroupNode>(schema_.schema_root()));
+    auto rg_writer = file_writer->AppendRowGroup();
+    auto col_writer = rg_writer->NextColumn();
+    col_writer->AddKeyValueMetadata(KeyValueMetadata::Make({"foo"}, {"bar"}));
+    file_writer->Close();
+  }
+  ASSERT_OK_AND_ASSIGN(auto buffer, sink->Finish());
+  auto file_reader =
+      ParquetFileReader::Open(std::make_shared<::arrow::io::BufferReader>(buffer));
+  auto key_value_metadata =
+      file_reader->metadata()->RowGroup(0)->ColumnChunk(0)->key_value_metadata();
+  ASSERT_THAT(key_value_metadata, NotNull());
+  ASSERT_EQ(1U, key_value_metadata->size());
+  ASSERT_OK_AND_ASSIGN(auto value, key_value_metadata->Get("foo"));
+  ASSERT_EQ("bar", value);
+}
+
 }  // namespace test
 }  // namespace parquet

cpp/src/parquet/metadata.cc

@@ -135,6 +135,36 @@ std::shared_ptr<Statistics> MakeColumnStats(const format::ColumnMetaData& meta_d
   throw ParquetException("Can't decode page statistics for selected column type");
 }
 
+template <typename Metadata>
+std::shared_ptr<KeyValueMetadata> CopyKeyValueMetadata(const Metadata& source) {
+  std::shared_ptr<KeyValueMetadata> metadata = nullptr;
+  if (source.__isset.key_value_metadata) {
+    std::vector<std::string> keys;
+    std::vector<std::string> values;
+    keys.reserve(source.key_value_metadata.size());
+    values.reserve(source.key_value_metadata.size());
+    for (const auto& it : source.key_value_metadata) {
+      keys.push_back(it.key);
+      values.push_back(it.value);
+    }
+    metadata = std::make_shared<KeyValueMetadata>(std::move(keys), std::move(values));
+  }
+  return metadata;
+}
+
+template <typename Metadata>
+void ToThriftKeyValueMetadata(const KeyValueMetadata& source, Metadata* metadata) {
+  std::vector<format::KeyValue> key_value_metadata;
+  key_value_metadata.reserve(static_cast<size_t>(source.size()));
+  for (int64_t i = 0; i < source.size(); ++i) {
+    format::KeyValue kv_pair;
+    kv_pair.__set_key(source.key(i));
+    kv_pair.__set_value(source.value(i));
+    key_value_metadata.emplace_back(std::move(kv_pair));
+  }
+  metadata->__set_key_value_metadata(std::move(key_value_metadata));
+}
+
 // MetaData Accessor
 
 // ColumnCryptoMetaData
@@ -233,6 +263,7 @@ class ColumnChunkMetaData::ColumnChunkMetaDataImpl {
                                  encoding_stats.count});
     }
     possible_stats_ = nullptr;
+    InitKeyValueMetadata();
   }
 
   bool Equals(const ColumnChunkMetaDataImpl& other) const {
@@ -343,7 +374,15 @@ class ColumnChunkMetaData::ColumnChunkMetaDataImpl {
     return std::nullopt;
   }
 
+  const std::shared_ptr<const KeyValueMetadata>& key_value_metadata() const {
+    return key_value_metadata_;
+  }
+
  private:
+  void InitKeyValueMetadata() {
+    key_value_metadata_ = CopyKeyValueMetadata(*column_metadata_);
+  }
+
   mutable std::shared_ptr<Statistics> possible_stats_;
   std::vector<Encoding::type> encodings_;
   std::vector<PageEncodingStats> encoding_stats_;
@@ -353,6 +392,7 @@ class ColumnChunkMetaData::ColumnChunkMetaDataImpl {
   const ColumnDescriptor* descr_;
   const ReaderProperties properties_;
   const ApplicationVersion* writer_version_;
+  std::shared_ptr<const KeyValueMetadata> key_value_metadata_;
 };
 
 std::unique_ptr<ColumnChunkMetaData> ColumnChunkMetaData::Make(
@@ -471,6 +511,11 @@ bool ColumnChunkMetaData::Equals(const ColumnChunkMetaData& other) const {
   return impl_->Equals(*other.impl_);
 }
 
+const std::shared_ptr<const KeyValueMetadata>& ColumnChunkMetaData::key_value_metadata()
+    const {
+  return impl_->key_value_metadata();
+}
+
 // row-group metadata
 class RowGroupMetaData::RowGroupMetaDataImpl {
  public:
@@ -913,7 +958,7 @@ class FileMetaData::FileMetaDataImpl {
     std::vector<parquet::ColumnOrder> column_orders;
     if (metadata_->__isset.column_orders) {
       column_orders.reserve(metadata_->column_orders.size());
-      for (auto column_order : metadata_->column_orders) {
+      for (auto& column_order : metadata_->column_orders) {
         if (column_order.__isset.TYPE_ORDER) {
           column_orders.push_back(ColumnOrder::type_defined_);
         } else {
@@ -927,16 +972,7 @@ class FileMetaData::FileMetaDataImpl {
     schema_.updateColumnOrders(column_orders);
   }
 
-  void InitKeyValueMetadata() {
-    std::shared_ptr<KeyValueMetadata> metadata = nullptr;
-    if (metadata_->__isset.key_value_metadata) {
-      metadata = std::make_shared<KeyValueMetadata>();
-      for (const auto& it : metadata_->key_value_metadata) {
-        metadata->Append(it.key, it.value);
-      }
-    }
-    key_value_metadata_ = std::move(metadata);
-  }
+  void InitKeyValueMetadata() { key_value_metadata_ = CopyKeyValueMetadata(*metadata_); }
 };
 
 std::shared_ptr<FileMetaData> FileMetaData::Make(
@@ -1590,6 +1626,10 @@ class ColumnChunkMetaDataBuilder::ColumnChunkMetaDataBuilderImpl {
     column_chunk_->meta_data.__set_encodings(std::move(thrift_encodings));
     column_chunk_->meta_data.__set_encoding_stats(std::move(thrift_encoding_stats));
 
+    if (key_value_metadata_) {
+      ToThriftKeyValueMetadata(*key_value_metadata_, &column_chunk_->meta_data);
+    }
+
     const auto& encrypt_md =
         properties_->column_encryption_properties(column_->path()->ToDotString());
     // column is encrypted
@@ -1656,6 +1696,10 @@ class ColumnChunkMetaDataBuilder::ColumnChunkMetaDataBuilderImpl {
     return column_chunk_->meta_data.total_compressed_size;
   }
 
+  void SetKeyValueMetadata(std::shared_ptr<const KeyValueMetadata> key_value_metadata) {
+    key_value_metadata_ = std::move(key_value_metadata);
+  }
+
  private:
   void Init(format::ColumnChunk* column_chunk) {
     column_chunk_ = column_chunk;
@@ -1670,6 +1714,7 @@ class ColumnChunkMetaDataBuilder::ColumnChunkMetaDataBuilderImpl {
   std::unique_ptr<format::ColumnChunk> owned_column_chunk_;
   const std::shared_ptr<WriterProperties> properties_;
   const ColumnDescriptor* column_;
+  std::shared_ptr<const KeyValueMetadata> key_value_metadata_;
 };
 
 std::unique_ptr<ColumnChunkMetaDataBuilder> ColumnChunkMetaDataBuilder::Make(
@@ -1727,6 +1772,11 @@ void ColumnChunkMetaDataBuilder::SetStatistics(const EncodedStatistics& result)
   impl_->SetStatistics(result);
 }
 
+void ColumnChunkMetaDataBuilder::SetKeyValueMetadata(
+    std::shared_ptr<const KeyValueMetadata> key_value_metadata) {
+  impl_->SetKeyValueMetadata(std::move(key_value_metadata));
+}
+
 int64_t ColumnChunkMetaDataBuilder::total_compressed_size() const {
   return impl_->total_compressed_size();
 }
@@ -1925,16 +1975,7 @@ class FileMetaDataBuilder::FileMetaDataBuilderImpl {
       } else if (key_value_metadata) {
         key_value_metadata_ = key_value_metadata_->Merge(*key_value_metadata);
       }
-      metadata_->key_value_metadata.clear();
-      metadata_->key_value_metadata.reserve(
-          static_cast<size_t>(key_value_metadata_->size()));
-      for (int64_t i = 0; i < key_value_metadata_->size(); ++i) {
-        format::KeyValue kv_pair;
-        kv_pair.__set_key(key_value_metadata_->key(i));
-        kv_pair.__set_value(key_value_metadata_->value(i));
-        metadata_->key_value_metadata.push_back(std::move(kv_pair));
-      }
-      metadata_->__isset.key_value_metadata = true;
+      ToThriftKeyValueMetadata(*key_value_metadata_, metadata_.get());
     }
 
     int32_t file_version = 0;

cpp/src/parquet/metadata.h

@@ -184,6 +184,7 @@ class PARQUET_EXPORT ColumnChunkMetaData {
   std::unique_ptr<ColumnCryptoMetaData> crypto_metadata() const;
   std::optional<IndexLocation> GetColumnIndexLocation() const;
   std::optional<IndexLocation> GetOffsetIndexLocation() const;
+  const std::shared_ptr<const KeyValueMetadata>& key_value_metadata() const;
 
  private:
   explicit ColumnChunkMetaData(
@@ -466,8 +467,12 @@ class PARQUET_EXPORT ColumnChunkMetaDataBuilder {
   // column chunk
   // Used when a dataset is spread across multiple files
   void set_file_path(const std::string& path);
+
   // column metadata
   void SetStatistics(const EncodedStatistics& stats);
+
+  void SetKeyValueMetadata(std::shared_ptr<const KeyValueMetadata> key_value_metadata);
+
   // get the column descriptor
   const ColumnDescriptor* descr() const;