feat(avro): extract avro datum from arrow array

src/iceberg/avro/avro_data_util.cc

@@ -17,6 +17,8 @@
  * under the License.
  */
 
+#include <ranges>
+
 #include <arrow/array/builder_binary.h>
 #include <arrow/array/builder_decimal.h>
 #include <arrow/array/builder_nested.h>
@@ -451,4 +453,217 @@ Status AppendDatumToBuilder(const ::avro::NodePtr& avro_node,
                                     projected_schema, array_builder);
 }
 
+namespace {
+
+// ToAvroNodeVisitor uses 0 for null branch and 1 for value branch.
+constexpr int64_t kNullBranch = 0;
+constexpr int64_t kValueBranch = 1;
+
+}  // namespace
+
+Status ExtractDatumFromArray(const ::arrow::Array& array, int64_t index,
+                             ::avro::GenericDatum* datum) {
+  if (index < 0 || index >= array.length()) {
+    return InvalidArgument("Cannot extract datum from array at index {} of length {}",
+                           index, array.length());
+  }
+
+  if (array.IsNull(index)) {
+    if (!datum->isUnion()) [[unlikely]] {
+      return InvalidSchema("Cannot extract null to non-union type: {}",
+                           ::avro::toString(datum->type()));
+    }
+    datum->selectBranch(kNullBranch);
+    return {};
+  }
+
+  if (datum->isUnion()) {
+    datum->selectBranch(kValueBranch);
+  }
+
+  switch (array.type()->id()) {
+    case ::arrow::Type::BOOL: {
+      const auto& bool_array =
+          internal::checked_cast<const ::arrow::BooleanArray&>(array);
+      datum->value<bool>() = bool_array.Value(index);
+      return {};
+    }
+
+    case ::arrow::Type::INT32: {
+      const auto& int32_array = internal::checked_cast<const ::arrow::Int32Array&>(array);
+      datum->value<int32_t>() = int32_array.Value(index);
+      return {};
+    }
+
+    case ::arrow::Type::INT64: {
+      const auto& int64_array = internal::checked_cast<const ::arrow::Int64Array&>(array);
+      datum->value<int64_t>() = int64_array.Value(index);
+      return {};
+    }
+
+    case ::arrow::Type::FLOAT: {
+      const auto& float_array = internal::checked_cast<const ::arrow::FloatArray&>(array);
+      datum->value<float>() = float_array.Value(index);
+      return {};
+    }
+
+    case ::arrow::Type::DOUBLE: {
+      const auto& double_array =
+          internal::checked_cast<const ::arrow::DoubleArray&>(array);
+      datum->value<double>() = double_array.Value(index);
+      return {};
+    }
+
+    case ::arrow::Type::STRING: {
+      const auto& string_array =
+          internal::checked_cast<const ::arrow::StringArray&>(array);
+      datum->value<std::string>() = string_array.GetString(index);
+      return {};
+    }
+
+    case ::arrow::Type::BINARY: {
+      const auto& binary_array =
+          internal::checked_cast<const ::arrow::BinaryArray&>(array);
+      std::string_view value = binary_array.GetView(index);
+      datum->value<std::vector<uint8_t>>().assign(
+          reinterpret_cast<const uint8_t*>(value.data()),
+          reinterpret_cast<const uint8_t*>(value.data()) + value.size());
+      return {};
+    }
+
+    case ::arrow::Type::FIXED_SIZE_BINARY: {
+      const auto& fixed_array =
+          internal::checked_cast<const ::arrow::FixedSizeBinaryArray&>(array);
+      std::string_view value = fixed_array.GetView(index);
+      auto& fixed_datum = datum->value<::avro::GenericFixed>();
+      fixed_datum.value().assign(
+          reinterpret_cast<const char*>(value.data()),
+          reinterpret_cast<const char*>(value.data()) + value.size());
+      return {};
+    }
+
+    case ::arrow::Type::DECIMAL128: {
+      const auto& decimal_array =
+          internal::checked_cast<const ::arrow::Decimal128Array&>(array);
+      std::string_view decimal_value = decimal_array.GetView(index);
+      auto& fixed_datum = datum->value<::avro::GenericFixed>();
+      auto& bytes = fixed_datum.value();
+      bytes.assign(decimal_value.begin(), decimal_value.end());
+      std::ranges::reverse(bytes);
+      return {};
+    }
+
+    case ::arrow::Type::DATE32: {
+      const auto& date_array = internal::checked_cast<const ::arrow::Date32Array&>(array);
+      datum->value<int32_t>() = date_array.Value(index);
+      return {};
+    }
+
+    case ::arrow::Type::TIME64: {
+      const auto& time_array = internal::checked_cast<const ::arrow::Time64Array&>(array);
+      datum->value<int64_t>() = time_array.Value(index);
+      return {};
+    }
+
+    // For both timestamp and timestamp_tz with time unit as microsecond.
+    case ::arrow::Type::TIMESTAMP: {
+      const auto& timestamp_array =
+          internal::checked_cast<const ::arrow::TimestampArray&>(array);
+      datum->value<int64_t>() = timestamp_array.Value(index);
+      return {};
+    }
+
+      // TODO(gangwu): support uuid type.
+
+    case ::arrow::Type::STRUCT: {
+      const auto& struct_array =
+          internal::checked_cast<const ::arrow::StructArray&>(array);
+      auto& record = datum->value<::avro::GenericRecord>();
+      for (int i = 0; i < struct_array.num_fields(); ++i) {
+        ICEBERG_RETURN_UNEXPECTED(
+            ExtractDatumFromArray(*struct_array.field(i), index, &record.fieldAt(i)));
+      }
+      return {};
+    }
+
+    // TODO(gangwu): support LARGE_LIST.
+    case ::arrow::Type::LIST: {
+      const auto& list_array = internal::checked_cast<const ::arrow::ListArray&>(array);
+      auto& avro_array = datum->value<::avro::GenericArray>();
+      auto& elements = avro_array.value();
+
+      auto start = list_array.value_offset(index);
+      auto end = list_array.value_offset(index + 1);
+      auto length = end - start;
+
+      auto values = list_array.values();
+      elements.resize(length, ::avro::GenericDatum(avro_array.schema()->leafAt(0)));
+
+      for (int64_t i = 0; i < length; ++i) {
+        ICEBERG_RETURN_UNEXPECTED(
+            ExtractDatumFromArray(*values, start + i, &elements[i]));
+      }
+      return {};
+    }
+
+    case ::arrow::Type::MAP: {
+      const auto& map_array = internal::checked_cast<const ::arrow::MapArray&>(array);
+      auto start = map_array.value_offset(index);
+      auto end = map_array.value_offset(index + 1);
+      auto length = end - start;
+
+      auto keys = map_array.keys();
+      auto items = map_array.items();
+
+      if (datum->type() == ::avro::AVRO_MAP) {
+        // Handle regular Avro map
+        auto& avro_map = datum->value<::avro::GenericMap>();
+        auto value_node = avro_map.schema()->leafAt(1);
+
+        auto& map_entries = avro_map.value();
+        map_entries.resize(
+            length, std::make_pair(std::string(), ::avro::GenericDatum(value_node)));
+
+        const auto& key_array =
+            internal::checked_cast<const ::arrow::StringArray&>(*keys);
+
+        for (int64_t i = 0; i < length; ++i) {
+          auto& map_entry = map_entries[i];
+          map_entry.first = key_array.GetString(start + i);
+          ICEBERG_RETURN_UNEXPECTED(
+              ExtractDatumFromArray(*items, start + i, &map_entry.second));
+        }
+      } else if (datum->type() == ::avro::AVRO_ARRAY) {
+        // Handle array-based map (list<struct<key, value>>)
+        auto& avro_array = datum->value<::avro::GenericArray>();
+        auto record_node = avro_array.schema()->leafAt(0);
+        if (record_node->type() != ::avro::AVRO_RECORD || record_node->leaves() != 2) {
+          return InvalidArgument(
+              "Expected Avro record with 2 fields for map value, got: {}",
+              ToString(record_node));
+        }
+
+        auto& elements = avro_array.value();
+        elements.resize(length, ::avro::GenericDatum(record_node));
+
+        for (int64_t i = 0; i < length; ++i) {
+          auto& record = elements[i].value<::avro::GenericRecord>();
+          ICEBERG_RETURN_UNEXPECTED(
+              ExtractDatumFromArray(*keys, start + i, &record.fieldAt(0)));
+          ICEBERG_RETURN_UNEXPECTED(
+              ExtractDatumFromArray(*items, start + i, &record.fieldAt(1)));
+        }
+      } else {
+        return InvalidArgument("Unsupported Avro type for map: {}",
+                               static_cast<int>(datum->type()));
+      }
+      return {};
+    }
+
+    default:
+      return InvalidArgument("Unsupported Arrow array type: {}",
+                             array.type()->ToString());
+  }
+}
+
 }  // namespace iceberg::avro

src/iceberg/avro/avro_data_util_internal.h

@@ -43,4 +43,13 @@ Status AppendDatumToBuilder(const ::avro::NodePtr& avro_node,
                             const Schema& projected_schema,
                             ::arrow::ArrayBuilder* array_builder);
 
+/// \brief Extract an Avro datum from an Arrow array.
+///
+/// \param array The Arrow array to extract from.
+/// \param index The index of the element to extract.
+/// \param datum The Avro datum to extract to. Its Avro type should be consistent with the
+/// Arrow type.
+Status ExtractDatumFromArray(const ::arrow::Array& array, int64_t index,
+                             ::avro::GenericDatum* datum);
+
 }  // namespace iceberg::avro