shangxinli commented on code in PR #592:
URL: https://github.com/apache/iceberg-cpp/pull/592#discussion_r2996571613


##########
src/iceberg/update/expire_snapshots.cc:
##########
@@ -285,7 +291,247 @@ Result<ExpireSnapshots::ApplyResult> 
ExpireSnapshots::Apply() {
                           });
   }
 
+  // Cache the result for use during Finalize()
+  apply_result_ = result;
+
   return result;
 }
 
+Status ExpireSnapshots::Finalize(std::optional<Error> commit_error) {
+  if (commit_error.has_value()) {
+    return {};
+  }
+
+  if (cleanup_level_ == CleanupLevel::kNone) {
+    return {};
+  }
+
+  if (!apply_result_.has_value() || 
apply_result_->snapshot_ids_to_remove.empty()) {
+    return {};
+  }
+
+  // File cleanup is best-effort: log and continue on individual file deletion 
failures
+  // to avoid blocking metadata updates (matching Java behavior).
+  return CleanExpiredFiles(apply_result_->snapshot_ids_to_remove);
+}
+
+void ExpireSnapshots::DeleteFilePath(const std::string& path) {
+  try {
+    if (delete_func_) {
+      delete_func_(path);
+    } else {
+      auto status = ctx_->table->io()->DeleteFile(path);
+      // Best-effort: ignore NotFound (file already deleted) and other errors.
+      // Java uses suppressFailureWhenFinished + onFailure logging.
+      std::ignore = status;
+    }
+  } catch (...) {
+    // Suppress all exceptions during file cleanup to match Java's
+    // suppressFailureWhenFinished behavior.
+  }
+}
+
+Status ExpireSnapshots::ReadManifestsForSnapshot(
+    int64_t snapshot_id, std::unordered_set<std::string>& manifest_paths) {
+  const TableMetadata& metadata = base();
+  auto file_io = ctx_->table->io();
+
+  auto snapshot_result = metadata.SnapshotById(snapshot_id);
+  if (!snapshot_result.has_value()) {
+    return {};
+  }
+  auto& snapshot = snapshot_result.value();
+
+  SnapshotCache snapshot_cache(snapshot.get());
+  auto manifests_result = snapshot_cache.Manifests(file_io);
+  if (!manifests_result.has_value()) {
+    // Best-effort: skip this snapshot if we can't read its manifests
+    return {};
+  }
+
+  for (const auto& manifest : manifests_result.value()) {
+    manifest_paths.insert(manifest.manifest_path);
+  }
+
+  return {};
+}
+
+Status ExpireSnapshots::FindDataFilesToDelete(
+    const std::unordered_set<std::string>& manifests_to_delete,
+    const std::unordered_set<std::string>& retained_manifests,
+    std::unordered_set<std::string>& data_files_to_delete) {
+  const TableMetadata& metadata = base();
+  auto file_io = ctx_->table->io();
+
+  // Step 1: Collect all file paths from manifests being deleted
+  for (const auto& manifest_path : manifests_to_delete) {
+    // Find the ManifestFile for this path by scanning expired snapshots
+    for (const auto& snapshot : metadata.snapshots) {
+      if (!snapshot) continue;
+      SnapshotCache snapshot_cache(snapshot.get());
+      auto manifests_result = snapshot_cache.Manifests(file_io);
+      if (!manifests_result.has_value()) continue;
+
+      for (const auto& manifest : manifests_result.value()) {
+        if (manifest.manifest_path != manifest_path) continue;
+
+        auto schema_result = metadata.Schema();
+        if (!schema_result.has_value()) continue;
+        auto spec_result = 
metadata.PartitionSpecById(manifest.partition_spec_id);
+        if (!spec_result.has_value()) continue;
+
+        auto reader_result = ManifestReader::Make(
+            manifest, file_io, schema_result.value(), spec_result.value());
+        if (!reader_result.has_value()) continue;
+
+        auto entries_result = reader_result.value()->Entries();
+        if (!entries_result.has_value()) continue;
+
+        for (const auto& entry : entries_result.value()) {
+          if (entry.data_file) {
+            data_files_to_delete.insert(entry.data_file->file_path);
+          }
+        }
+        goto next_manifest;  // Found and processed this manifest, move to next
+      }
+    }
+  next_manifest:;
+  }
+
+  if (data_files_to_delete.empty()) {
+    return {};
+  }
+
+  // Step 2: Remove any files that are still referenced by retained manifests.
+  // This ensures we don't delete files that are shared across manifests.
+  for (const auto& manifest_path : retained_manifests) {
+    if (data_files_to_delete.empty()) break;
+
+    for (const auto& snapshot : metadata.snapshots) {
+      if (!snapshot) continue;
+      SnapshotCache snapshot_cache(snapshot.get());
+      auto manifests_result = snapshot_cache.Manifests(file_io);
+      if (!manifests_result.has_value()) continue;
+
+      for (const auto& manifest : manifests_result.value()) {
+        if (manifest.manifest_path != manifest_path) continue;
+
+        auto schema_result = metadata.Schema();
+        if (!schema_result.has_value()) continue;
+        auto spec_result = 
metadata.PartitionSpecById(manifest.partition_spec_id);
+        if (!spec_result.has_value()) continue;
+
+        auto reader_result = ManifestReader::Make(
+            manifest, file_io, schema_result.value(), spec_result.value());
+        if (!reader_result.has_value()) continue;
+
+        auto entries_result = reader_result.value()->Entries();

Review Comment:
   Fixed — changed to `LiveEntries()` here as well, consistent with Step 1.



##########
src/iceberg/update/expire_snapshots.cc:
##########
@@ -285,7 +291,247 @@ Result<ExpireSnapshots::ApplyResult> 
ExpireSnapshots::Apply() {
                           });
   }
 
+  // Cache the result for use during Finalize()
+  apply_result_ = result;
+
   return result;
 }
 
+Status ExpireSnapshots::Finalize(std::optional<Error> commit_error) {
+  if (commit_error.has_value()) {
+    return {};
+  }
+
+  if (cleanup_level_ == CleanupLevel::kNone) {
+    return {};
+  }
+
+  if (!apply_result_.has_value() || 
apply_result_->snapshot_ids_to_remove.empty()) {
+    return {};
+  }
+
+  // File cleanup is best-effort: log and continue on individual file deletion 
failures
+  // to avoid blocking metadata updates (matching Java behavior).
+  return CleanExpiredFiles(apply_result_->snapshot_ids_to_remove);
+}
+
+void ExpireSnapshots::DeleteFilePath(const std::string& path) {
+  try {
+    if (delete_func_) {
+      delete_func_(path);
+    } else {
+      auto status = ctx_->table->io()->DeleteFile(path);
+      // Best-effort: ignore NotFound (file already deleted) and other errors.
+      // Java uses suppressFailureWhenFinished + onFailure logging.
+      std::ignore = status;
+    }
+  } catch (...) {
+    // Suppress all exceptions during file cleanup to match Java's
+    // suppressFailureWhenFinished behavior.
+  }
+}
+
+Status ExpireSnapshots::ReadManifestsForSnapshot(
+    int64_t snapshot_id, std::unordered_set<std::string>& manifest_paths) {
+  const TableMetadata& metadata = base();
+  auto file_io = ctx_->table->io();
+
+  auto snapshot_result = metadata.SnapshotById(snapshot_id);
+  if (!snapshot_result.has_value()) {
+    return {};
+  }
+  auto& snapshot = snapshot_result.value();
+
+  SnapshotCache snapshot_cache(snapshot.get());
+  auto manifests_result = snapshot_cache.Manifests(file_io);
+  if (!manifests_result.has_value()) {
+    // Best-effort: skip this snapshot if we can't read its manifests
+    return {};
+  }
+
+  for (const auto& manifest : manifests_result.value()) {
+    manifest_paths.insert(manifest.manifest_path);
+  }
+
+  return {};
+}
+
+Status ExpireSnapshots::FindDataFilesToDelete(
+    const std::unordered_set<std::string>& manifests_to_delete,
+    const std::unordered_set<std::string>& retained_manifests,
+    std::unordered_set<std::string>& data_files_to_delete) {
+  const TableMetadata& metadata = base();
+  auto file_io = ctx_->table->io();
+
+  // Step 1: Collect all file paths from manifests being deleted
+  for (const auto& manifest_path : manifests_to_delete) {
+    // Find the ManifestFile for this path by scanning expired snapshots
+    for (const auto& snapshot : metadata.snapshots) {
+      if (!snapshot) continue;
+      SnapshotCache snapshot_cache(snapshot.get());
+      auto manifests_result = snapshot_cache.Manifests(file_io);
+      if (!manifests_result.has_value()) continue;
+
+      for (const auto& manifest : manifests_result.value()) {
+        if (manifest.manifest_path != manifest_path) continue;
+
+        auto schema_result = metadata.Schema();
+        if (!schema_result.has_value()) continue;
+        auto spec_result = 
metadata.PartitionSpecById(manifest.partition_spec_id);
+        if (!spec_result.has_value()) continue;
+
+        auto reader_result = ManifestReader::Make(
+            manifest, file_io, schema_result.value(), spec_result.value());
+        if (!reader_result.has_value()) continue;
+
+        auto entries_result = reader_result.value()->Entries();
+        if (!entries_result.has_value()) continue;
+
+        for (const auto& entry : entries_result.value()) {
+          if (entry.data_file) {
+            data_files_to_delete.insert(entry.data_file->file_path);
+          }
+        }
+        goto next_manifest;  // Found and processed this manifest, move to next
+      }
+    }
+  next_manifest:;
+  }
+
+  if (data_files_to_delete.empty()) {
+    return {};
+  }
+
+  // Step 2: Remove any files that are still referenced by retained manifests.
+  // This ensures we don't delete files that are shared across manifests.
+  for (const auto& manifest_path : retained_manifests) {
+    if (data_files_to_delete.empty()) break;
+
+    for (const auto& snapshot : metadata.snapshots) {
+      if (!snapshot) continue;
+      SnapshotCache snapshot_cache(snapshot.get());
+      auto manifests_result = snapshot_cache.Manifests(file_io);
+      if (!manifests_result.has_value()) continue;
+
+      for (const auto& manifest : manifests_result.value()) {
+        if (manifest.manifest_path != manifest_path) continue;
+
+        auto schema_result = metadata.Schema();
+        if (!schema_result.has_value()) continue;
+        auto spec_result = 
metadata.PartitionSpecById(manifest.partition_spec_id);
+        if (!spec_result.has_value()) continue;
+
+        auto reader_result = ManifestReader::Make(
+            manifest, file_io, schema_result.value(), spec_result.value());
+        if (!reader_result.has_value()) continue;
+
+        auto entries_result = reader_result.value()->Entries();
+        if (!entries_result.has_value()) continue;
+
+        for (const auto& entry : entries_result.value()) {
+          if (entry.data_file) {
+            data_files_to_delete.erase(entry.data_file->file_path);
+          }
+        }
+        goto next_retained;
+      }
+    }
+  next_retained:;
+  }
+
+  return {};
+}
+
+Status ExpireSnapshots::CleanExpiredFiles(
+    const std::vector<int64_t>& expired_snapshot_ids) {
+  const TableMetadata& metadata = base();
+
+  // Build expired and retained snapshot ID sets.
+  // The retained set includes ALL snapshots referenced by any branch or tag,
+  // since Apply() already computed retention across all refs.
+  std::unordered_set<int64_t> expired_id_set(expired_snapshot_ids.begin(),
+                                             expired_snapshot_ids.end());
+  std::unordered_set<int64_t> retained_snapshot_ids;
+  for (const auto& snapshot : metadata.snapshots) {
+    if (snapshot && !expired_id_set.contains(snapshot->snapshot_id)) {
+      retained_snapshot_ids.insert(snapshot->snapshot_id);
+    }
+  }
+
+  // Phase 1: Collect manifest paths from expired and retained snapshots.
+  // TODO(shangxinli): Parallelize manifest collection with a thread pool.
+  std::unordered_set<std::string> expired_manifest_paths;
+  for (int64_t snapshot_id : expired_snapshot_ids) {
+    std::ignore = ReadManifestsForSnapshot(snapshot_id, 
expired_manifest_paths);
+  }
+
+  std::unordered_set<std::string> retained_manifest_paths;
+  for (int64_t snapshot_id : retained_snapshot_ids) {
+    std::ignore = ReadManifestsForSnapshot(snapshot_id, 
retained_manifest_paths);
+  }
+
+  // Phase 2: Prune manifests still referenced by retained snapshots.
+  // Only manifests exclusively in expired snapshots should be deleted.
+  std::unordered_set<std::string> manifests_to_delete;
+  for (const auto& path : expired_manifest_paths) {
+    if (!retained_manifest_paths.contains(path)) {
+      manifests_to_delete.insert(path);
+    }
+  }
+
+  // Phase 3: If cleanup level is kAll, find data files to delete.
+  // Only read entries from manifests being deleted (not all expired 
manifests),
+  // then subtract any files still reachable from retained manifests.
+  if (cleanup_level_ == CleanupLevel::kAll && !manifests_to_delete.empty()) {
+    std::unordered_set<std::string> data_files_to_delete;
+    std::ignore = FindDataFilesToDelete(manifests_to_delete, 
retained_manifest_paths,
+                                        data_files_to_delete);
+
+    // TODO(shangxinli): Parallelize file deletion with a thread pool.
+    for (const auto& path : data_files_to_delete) {
+      DeleteFilePath(path);
+    }
+  }
+
+  // Phase 4: Delete orphaned manifest files.
+  for (const auto& path : manifests_to_delete) {
+    DeleteFilePath(path);
+  }
+
+  // Phase 5: Delete manifest lists from expired snapshots.
+  for (int64_t snapshot_id : expired_snapshot_ids) {
+    auto snapshot_result = metadata.SnapshotById(snapshot_id);
+    if (!snapshot_result.has_value()) continue;
+    auto& snapshot = snapshot_result.value();
+    if (!snapshot->manifest_list.empty()) {
+      DeleteFilePath(snapshot->manifest_list);
+    }
+  }
+
+  // Phase 6: Delete expired statistics files.
+  // Use set difference between before and after states (matching Java 
behavior).
+  // Since Finalize runs before table_ is updated, "after" is base() minus 
expired.
+  std::unordered_set<int64_t> retained_stats_snapshots(retained_snapshot_ids);
+  for (const auto& stat_file : metadata.statistics) {
+    if (stat_file && 
!retained_stats_snapshots.contains(stat_file->snapshot_id)) {

Review Comment:
   Good point. Changed to path-based set difference: collect paths from 
retained snapshots first, then only delete expired statistics files whose paths 
are not in the retained set. This prevents erroneous deletion when a statistics 
file path is shared across snapshots



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