feat: metrics for avro writer

src/iceberg/CMakeLists.txt

@@ -178,6 +178,7 @@ if(ICEBERG_BUILD_BUNDLE)
       avro/avro_data_util.cc
       avro/avro_direct_decoder.cc
       avro/avro_direct_encoder.cc
+      avro/avro_metrics.cc
       avro/avro_reader.cc
       avro/avro_writer.cc
       avro/avro_register.cc

src/iceberg/avro/avro_metrics.cc

@@ -0,0 +1,31 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+#include "iceberg/avro/avro_metrics.h"
+
+namespace iceberg::avro {
+
+Metrics AvroMetrics::GetMetrics(const Schema& /*schema*/, int64_t num_records,
+                                const MetricsConfig& /*metrics_config*/) {
+  // TODO(WZhuo) will populate in following PRs if datum writer is a
+  // MetricsAwareDatumWriter
+  return Metrics{.row_count = num_records};
+}
+
+}  // namespace iceberg::avro

src/iceberg/avro/avro_metrics.h

@@ -0,0 +1,46 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+#pragma once
+
+#include "iceberg/iceberg_bundle_export.h"
+#include "iceberg/metrics.h"
+
+namespace iceberg {
+class Schema;
+class MetricsConfig;
+}  // namespace iceberg
+
+namespace iceberg::avro {
+
+/// \brief Utility class for computing Avro file metrics.
+class ICEBERG_BUNDLE_EXPORT AvroMetrics {
+ public:
+  AvroMetrics() = delete;
+
+  /// \brief Compute metrics from writer state.
+  /// \param schema The Iceberg schema of the written data.
+  /// \param num_records The number of records written.
+  /// \param metrics_config The metrics configuration.
+  /// \return Metrics for the written Avro file.
+  static Metrics GetMetrics(const Schema& schema, int64_t num_records,
+                            const MetricsConfig& metrics_config);
+};
+
+}  // namespace iceberg::avro

src/iceberg/avro/avro_writer.cc

@@ -33,9 +33,11 @@
 #include "iceberg/arrow/arrow_status_internal.h"
 #include "iceberg/avro/avro_data_util_internal.h"
 #include "iceberg/avro/avro_direct_encoder_internal.h"
+#include "iceberg/avro/avro_metrics.h"
 #include "iceberg/avro/avro_register.h"
 #include "iceberg/avro/avro_schema_util_internal.h"
 #include "iceberg/avro/avro_stream_internal.h"
+#include "iceberg/metrics_config.h"
 #include "iceberg/schema.h"
 #include "iceberg/schema_internal.h"
 #include "iceberg/util/checked_cast.h"
@@ -238,6 +240,7 @@ class AvroWriter::Impl {
       ICEBERG_RETURN_UNEXPECTED(backend_->WriteRow(*write_schema_, *result, i));
     }
 
+    num_records_ += result->length();
     return {};
   }
 
@@ -261,6 +264,14 @@ class AvroWriter::Impl {
     return current_pos;
   }
 
+  Result<Metrics> metrics() const {
+    if (!Closed()) {
+      return Invalid("AvroWriter is not closed");
+    }
+    return AvroMetrics::GetMetrics(*write_schema_, num_records_,
+                                   *MetricsConfig::Default());
+  }
+
  private:
   // The schema to write.
   std::shared_ptr<::iceberg::Schema> write_schema_;
@@ -272,6 +283,8 @@ class AvroWriter::Impl {
   ArrowSchema arrow_schema_;
   // Total length of the written Avro file.
   int64_t total_bytes_ = 0;
+  // Number of records written.
+  int64_t num_records_ = 0;
   // The write backend to write data.
   std::unique_ptr<AvroWriteBackend> backend_;
 };
@@ -292,13 +305,7 @@ Status AvroWriter::Close() {
   return {};
 }
 
-Result<Metrics> AvroWriter::metrics() {
-  if (impl_->Closed()) {
-    // TODO(xiao.dong) implement metrics
-    return {};
-  }
-  return Invalid("AvroWriter is not closed");
-}
+Result<Metrics> AvroWriter::metrics() { return impl_->metrics(); }
 
 Result<int64_t> AvroWriter::length() { return impl_->length(); }
 

src/iceberg/test/avro_test.cc

@@ -936,6 +936,44 @@ TEST_P(AvroWriterTest, MultipleAvroBlocks) {
   }
 }
 
+TEST_P(AvroWriterTest, Metrics) {
+  auto schema = std::make_shared<iceberg::Schema>(std::vector<SchemaField>{
+      SchemaField::MakeRequired(1, "id", std::make_shared<IntType>()),
+      SchemaField::MakeOptional(2, "name", std::make_shared<StringType>())});
+
+  std::string test_data = R"([[1, "Alice"], [2, "Bob"], [3, "Charlie"]])";
+
+  // Write data but don't close yet
+  ArrowSchema arrow_c_schema;
+  ASSERT_THAT(ToArrowSchema(*schema, &arrow_c_schema), IsOk());
+  auto arrow_schema = ::arrow::ImportType(&arrow_c_schema).ValueOrDie();
+  auto array = ::arrow::json::ArrayFromJSONString(arrow_schema, test_data).ValueOrDie();
+  struct ArrowArray arrow_array;
+  ASSERT_TRUE(::arrow::ExportArray(*array, &arrow_array).ok());
+
+  ICEBERG_UNWRAP_OR_FAIL(
+      writer_,
+      WriterFactoryRegistry::Open(
+          FileFormatType::kAvro,
+          {.path = temp_avro_file_, .schema = schema, .io = file_io_, .properties = {}}));
+  ASSERT_THAT(writer_->Write(&arrow_array), IsOk());
+
+  // Metrics should fail before close
+  ASSERT_THAT(writer_->metrics(), IsError(ErrorKind::kInvalid));
+
+  // After close, metrics should succeed
+  ASSERT_THAT(writer_->Close(), IsOk());
+  ICEBERG_UNWRAP_OR_FAIL(auto metrics, writer_->metrics());
+  ASSERT_TRUE(metrics.row_count.has_value());
+  EXPECT_EQ(metrics.row_count.value(), 3);
+  EXPECT_TRUE(metrics.column_sizes.empty());
+  EXPECT_TRUE(metrics.value_counts.empty());
+  EXPECT_TRUE(metrics.null_value_counts.empty());
+  EXPECT_TRUE(metrics.nan_value_counts.empty());
+  EXPECT_TRUE(metrics.lower_bounds.empty());
+  EXPECT_TRUE(metrics.upper_bounds.empty());
+}
+
 // Instantiate parameterized tests for both direct encoder and GenericDatum paths
 INSTANTIATE_TEST_SUITE_P(DirectEncoderModes, AvroWriterTest,
                          ::testing::Values(true, false),