1 files changed, 211 insertions, 202 deletions

diff --git a/src/tangara/database/database.cpp b/src/tangara/database/database.cpp
index 85700431..64451f48 100644
--- a/src/tangara/database/database.cpp
+++ b/src/tangara/database/database.cpp
@@ -6,9 +6,6 @@
 
 #include "database/database.hpp"
 
-#include <stdint.h>
-#include <sys/_stdint.h>
-
 #include <algorithm>
 #include <cstdint>
 #include <functional>
@@ -20,10 +17,8 @@
 #include <string>
 #include <variant>
 
-#include "collation.hpp"
 #include "cppbor.h"
 #include "cppbor_parse.h"
-#include "database/index.hpp"
 #include "esp_log.h"
 #include "esp_timer.h"
 #include "ff.h"
@@ -37,13 +32,14 @@
 #include "leveldb/status.h"
 #include "leveldb/write_batch.h"
 
+#include "collation.hpp"
 #include "database/db_events.hpp"
 #include "database/env_esp.hpp"
-#include "database/file_gatherer.hpp"
+#include "database/index.hpp"
 #include "database/records.hpp"
 #include "database/tag_parser.hpp"
 #include "database/track.hpp"
-#include "drivers/spi.hpp"
+#include "database/track_finder.hpp"
 #include "events/event_queue.hpp"
 #include "memory_resource.hpp"
 #include "result.hpp"
@@ -55,15 +51,19 @@ static SingletonEnv<leveldb::EspEnv> sEnv;
 [[maybe_unused]] static const char* kTag = "DB";
 
 static const char kDbPath[] = "/.tangara-db";
+static const char kMusicPath[] = "Music";
 
 static const char kKeyDbVersion[] = "schema_version";
-
 static const char kKeyCustom[] = "U\0";
 static const char kKeyCollator[] = "collator";
-static const char kKeyTrackId[] = "next_track_id";
+
+static constexpr size_t kMaxParallelism = 2;
 
 static std::atomic<bool> sIsDbOpen(false);
 
+using std::placeholders::_1;
+using std::placeholders::_2;
+
 static auto CreateNewDatabase(leveldb::Options& options, locale::ICollator& col)
     -> leveldb::DB* {
   Database::Destroy();
@@ -122,8 +122,7 @@ static auto CheckDatabase(leveldb::DB& db, locale::ICollator& col) -> bool {
   return true;
 }
 
-auto Database::Open(IFileGatherer& gatherer,
-                    ITagParser& parser,
+auto Database::Open(ITagParser& parser,
                     locale::ICollator& collator,
                     tasks::WorkerPool& bg_worker)
     -> cpp::result<Database*, DatabaseError> {
@@ -144,10 +143,10 @@ auto Database::Open(IFileGatherer& gatherer,
 
             leveldb::Options options;
             options.env = sEnv.env();
-            options.write_buffer_size = 4 * 1024;
-            options.max_file_size = 16 * 1024;
+            // Match the write buffer size to the MMU page size in order to
+            // make most efficient use of PSRAM mapping.
+            options.write_buffer_size = CONFIG_MMU_PAGE_SIZE;
             options.block_cache = cache.get();
-            options.block_size = 2048;
 
             auto status = leveldb::DB::Open(options, kDbPath, &db);
             if (!status.ok()) {
@@ -168,7 +167,7 @@ auto Database::Open(IFileGatherer& gatherer,
             }
 
             ESP_LOGI(kTag, "Database opened successfully");
-            return new Database(db, cache.release(), gatherer, parser,
+            return new Database(db, cache.release(), bg_worker, parser,
                                 collator);
           })
       .get();
@@ -182,15 +181,21 @@ auto Database::Destroy() -> void {
 
 Database::Database(leveldb::DB* db,
                    leveldb::Cache* cache,
-                   IFileGatherer& file_gatherer,
+                   tasks::WorkerPool& pool,
                    ITagParser& tag_parser,
                    locale::ICollator& collator)
     : db_(db),
       cache_(cache),
-      file_gatherer_(file_gatherer),
+      track_finder_(
+          pool,
+          kMaxParallelism,
+          std::bind(&Database::processCandidateCallback, this, _1, _2),
+          std::bind(&Database::indexingCompleteCallback, this)),
       tag_parser_(tag_parser),
       collator_(collator),
-      is_updating_(false) {}
+      is_updating_(false) {
+  dbCalculateNextTrackId();
+}
 
 Database::~Database() {
   // Delete db_ first so that any outstanding background work finishes before
@@ -244,7 +249,7 @@ auto Database::get(const std::string& key) -> std::optional<std::string> {
 }
 
 auto Database::getTrackPath(TrackId id) -> std::optional<std::string> {
-  auto track_data = dbGetTrackData(id);
+  auto track_data = dbGetTrackData(leveldb::ReadOptions(), id);
   if (!track_data) {
     return {};
   }
@@ -252,7 +257,7 @@ auto Database::getTrackPath(TrackId id) -> std::optional<std::string> {
 }
 
 auto Database::getTrack(TrackId id) -> std::shared_ptr<Track> {
-  std::shared_ptr<TrackData> data = dbGetTrackData(id);
+  std::shared_ptr<TrackData> data = dbGetTrackData(leveldb::ReadOptions(), id);
   if (!data || data->is_tombstoned) {
     return {};
   }
@@ -275,34 +280,61 @@ auto Database::getIndexes() -> std::vector<IndexInfo> {
   };
 }
 
-class UpdateNotifier {
- public:
-  UpdateNotifier(std::atomic<bool>& is_updating) : is_updating_(is_updating) {
-    events::Ui().Dispatch(event::UpdateStarted{});
-    events::System().Dispatch(event::UpdateStarted{});
+Database::UpdateTracker::UpdateTracker()
+    : num_old_tracks_(0),
+      num_new_tracks_(0),
+      start_time_(esp_timer_get_time()) {
+  events::Ui().Dispatch(event::UpdateStarted{});
+  events::System().Dispatch(event::UpdateStarted{});
+}
+
+Database::UpdateTracker::~UpdateTracker() {
+  uint64_t end_time = esp_timer_get_time();
+
+  uint64_t time_per_old = 0;
+  if (num_old_tracks_) {
+    time_per_old = (verification_finish_time_ - start_time_) / num_old_tracks_;
   }
-  ~UpdateNotifier() {
-    is_updating_ = false;
-    events::Ui().Dispatch(event::UpdateFinished{});
-    events::System().Dispatch(event::UpdateFinished{});
+  uint64_t time_per_new = 0;
+  if (num_new_tracks_) {
+    time_per_new = (end_time - verification_finish_time_) / num_new_tracks_;
   }
 
- private:
-  std::atomic<bool>& is_updating_;
-};
+  ESP_LOGI(
+      kTag,
+      "processed %lu old tracks and %lu new tracks in %llu seconds (%llums "
+      "per old, %llums per new)",
+      num_old_tracks_, num_new_tracks_, (end_time - start_time_) / 1000000,
+      time_per_old / 1000, time_per_new / 1000);
+
+  events::Ui().Dispatch(event::UpdateFinished{});
+  events::System().Dispatch(event::UpdateFinished{});
+}
+
+auto Database::UpdateTracker::onTrackVerified() -> void {
+  events::Ui().Dispatch(event::UpdateProgress{
+      .stage = event::UpdateProgress::Stage::kVerifyingExistingTracks,
+      .val = ++num_old_tracks_,
+  });
+}
+
+auto Database::UpdateTracker::onVerificationFinished() -> void {
+  verification_finish_time_ = esp_timer_get_time();
+}
+
+auto Database::UpdateTracker::onTrackAdded() -> void {
+  num_new_tracks_++;
+}
 
 auto Database::updateIndexes() -> void {
   if (is_updating_.exchange(true)) {
     return;
   }
-  UpdateNotifier notifier{is_updating_};
-
-  uint32_t num_old_tracks = 0;
-  uint32_t num_new_tracks = 0;
-  uint64_t start_time = esp_timer_get_time();
+  update_tracker_ = std::make_unique<UpdateTracker>();
 
   leveldb::ReadOptions read_options;
-  read_options.fill_cache = true;
+  read_options.fill_cache = false;
+  read_options.verify_checksums = true;
 
   // Stage 1: verify all existing tracks are still valid.
   ESP_LOGI(kTag, "verifying existing tracks");
@@ -311,11 +343,7 @@ auto Database::updateIndexes() -> void {
     std::string prefix = EncodeDataPrefix();
     for (it->Seek(prefix); it->Valid() && it->key().starts_with(prefix);
          it->Next()) {
-      num_old_tracks++;
-      events::Ui().Dispatch(event::UpdateProgress{
-          .stage = event::UpdateProgress::Stage::kVerifyingExistingTracks,
-          .val = num_old_tracks,
-      });
+      update_tracker_->onTrackVerified();
 
       std::shared_ptr<TrackData> track = ParseDataValue(it->value());
       if (!track) {
@@ -326,7 +354,6 @@ auto Database::updateIndexes() -> void {
       }
 
       if (track->is_tombstoned) {
-        ESP_LOGW(kTag, "skipping tombstoned %lx", track->id);
         continue;
       }
 
@@ -349,11 +376,19 @@ auto Database::updateIndexes() -> void {
         // We couldn't read the tags for this track. Either they were
         // malformed, or perhaps the file is missing. Either way, tombstone
         // this record.
-        ESP_LOGW(kTag, "entombing missing #%lx", track->id);
+        ESP_LOGI(kTag, "entombing missing #%lx", track->id);
+
+        // Remove the indexes first, so that interrupted operations don't leave
+        // dangling index records.
         dbRemoveIndexes(track);
+
+        // Do the rest of the tombstoning as one atomic write.
+        leveldb::WriteBatch batch;
         track->is_tombstoned = true;
-        dbPutTrackData(*track);
-        db_->Delete(leveldb::WriteOptions{}, EncodePathKey(track->filepath));
+        batch.Put(EncodeDataKey(track->id), EncodeDataValue(*track));
+        batch.Delete(EncodePathKey(track->filepath));
+
+        db_->Write(leveldb::WriteOptions(), &batch);
         continue;
       }
 
@@ -367,204 +402,181 @@ auto Database::updateIndexes() -> void {
         // database.
         ESP_LOGI(kTag, "updating hash (%llx -> %llx)", track->tags_hash,
                  new_hash);
+
+        // Again, we remove the old index records first so has to avoid
+        // dangling references.
         dbRemoveIndexes(track);
 
+        // Atomically correct the hash + create the new index records.
+        leveldb::WriteBatch batch;
         track->tags_hash = new_hash;
-        dbIngestTagHashes(*tags, track->individual_tag_hashes);
-        dbPutTrackData(*track);
-        dbPutHash(new_hash, track->id);
+        dbIngestTagHashes(*tags, track->individual_tag_hashes, batch);
+
+        dbCreateIndexesForTrack(*track, *tags, batch);
+        batch.Put(EncodeDataKey(track->id), EncodeDataValue(*track));
+        batch.Put(EncodeHashKey(new_hash), EncodeHashValue(track->id));
+        db_->Write(leveldb::WriteOptions(), &batch);
       }
     }
   }
 
-  uint64_t verify_end_time = esp_timer_get_time();
+  update_tracker_->onVerificationFinished();
 
   // Stage 2: search for newly added files.
-  ESP_LOGI(kTag, "scanning for new tracks");
-  uint64_t num_files = 0;
-  file_gatherer_.FindFiles("", [&](std::string_view path, const FILINFO& info) {
-    num_files++;
-    events::Ui().Dispatch(event::UpdateProgress{
-        .stage = event::UpdateProgress::Stage::kScanningForNewTracks,
-        .val = num_files,
-    });
-
-    std::string unused;
-    if (db_->Get(read_options, EncodePathKey(path), &unused).ok()) {
-      // This file is already in the database; skip it.
-      return;
-    }
-
-    std::shared_ptr<TrackTags> tags = tag_parser_.ReadAndParseTags(path);
-    if (!tags || tags->encoding() == Container::kUnsupported) {
-      // No parseable tags; skip this fiile.
-      return;
-    }
+  std::string root;
+  FF_DIR dir;
+  if (f_opendir(&dir, kMusicPath) == FR_OK) {
+    f_closedir(&dir);
+    root = kMusicPath;
+  }
+  ESP_LOGI(kTag, "scanning for new tracks in '%s'", root.c_str());
+  track_finder_.launch(root);
+};
 
-    // Check for any existing record with the same hash.
-    uint64_t hash = tags->Hash();
-    std::string key = EncodeHashKey(hash);
-    std::optional<TrackId> existing_hash;
-    std::string raw_entry;
-    if (db_->Get(leveldb::ReadOptions(), key, &raw_entry).ok()) {
-      existing_hash = ParseHashValue(raw_entry);
-    }
+auto Database::processCandidateCallback(FILINFO& info, std::string_view path)
+    -> void {
+  leveldb::ReadOptions read_options;
+  read_options.fill_cache = true;
+  read_options.verify_checksums = false;
 
-    std::pair<uint16_t, uint16_t> modified{info.fdate, info.ftime};
-    if (!existing_hash) {
-      // We've never met this track before! Or we have, but the entry is
-      // malformed. Either way, record this as a new track.
-      TrackId id = dbMintNewTrackId();
-      ESP_LOGD(kTag, "recording new 0x%lx", id);
-      num_new_tracks++;
-
-      auto data = std::make_shared<TrackData>();
-      data->id = id;
-      data->filepath = path;
-      data->tags_hash = hash;
-      data->modified_at = modified;
-      dbIngestTagHashes(*tags, data->individual_tag_hashes);
-
-      dbPutTrackData(*data);
-      dbPutHash(hash, id);
-      auto t = std::make_shared<Track>(data, tags);
-      dbCreateIndexesForTrack(*t);
-      db_->Put(leveldb::WriteOptions{}, EncodePathKey(path),
-               TrackIdToBytes(id));
-      return;
-    }
+  std::string unused;
+  if (db_->Get(read_options, EncodePathKey(path), &unused).ok()) {
+    // This file is already in the database; skip it.
+    return;
+  }
 
-    std::shared_ptr<TrackData> existing_data = dbGetTrackData(*existing_hash);
-    if (!existing_data) {
-      // We found a hash that matches, but there's no data record? Weird.
-      auto new_data = std::make_shared<TrackData>();
-      new_data->id = dbMintNewTrackId();
-      new_data->filepath = path;
-      new_data->tags_hash = hash;
-      new_data->modified_at = modified;
-      dbIngestTagHashes(*tags, new_data->individual_tag_hashes);
-      dbPutTrackData(*new_data);
-      auto t = std::make_shared<Track>(new_data, tags);
-      dbCreateIndexesForTrack(*t);
-      db_->Put(leveldb::WriteOptions{}, EncodePathKey(path),
-               TrackIdToBytes(new_data->id));
-      return;
-    }
+  std::shared_ptr<TrackTags> tags = tag_parser_.ReadAndParseTags(path);
+  if (!tags || tags->encoding() == Container::kUnsupported) {
+    // No parseable tags; skip this fiile.
+    return;
+  }
 
-    if (existing_data->is_tombstoned) {
-      ESP_LOGI(kTag, "exhuming track %lu", existing_data->id);
-      existing_data->is_tombstoned = false;
-      existing_data->modified_at = modified;
-      dbPutTrackData(*existing_data);
-      auto t = std::make_shared<Track>(existing_data, tags);
-      dbCreateIndexesForTrack(*t);
-      db_->Put(leveldb::WriteOptions{}, EncodePathKey(path),
-               TrackIdToBytes(existing_data->id));
-    } else if (existing_data->filepath !=
-               std::pmr::string{path.data(), path.size()}) {
+  // Check for any existing track with the same hash.
+  uint64_t hash = tags->Hash();
+  std::optional<TrackId> existing_id;
+  std::string raw_entry;
+  if (db_->Get(read_options, EncodeHashKey(hash), &raw_entry).ok()) {
+    existing_id = ParseHashValue(raw_entry);
+  }
+
+  std::shared_ptr<TrackData> data;
+  if (existing_id) {
+    // Do we have any existing data for this track? This could be the case if
+    // this is a tombstoned entry. In such as case, we want to reuse the
+    // previous TrackData so that any extra metadata is preserved.
+    data = dbGetTrackData(read_options, *existing_id);
+    if (!data) {
+      data = std::make_shared<TrackData>();
+      data->id = *existing_id;
+    } else if (data->filepath != path && !data->is_tombstoned) {
       ESP_LOGW(kTag, "hash collision: %s, %s, %s",
                tags->title().value_or("no title").c_str(),
                tags->artist().value_or("no artist").c_str(),
                tags->album().value_or("no album").c_str());
+      // Don't commit anything if there's a hash collision, since we're
+      // likely to make a big mess.
+      return;
     }
-  });
+  } else {
+    update_tracker_->onTrackAdded();
+    data = std::make_shared<TrackData>();
+    data->id = dbMintNewTrackId();
+  }
 
-  uint64_t end_time = esp_timer_get_time();
+  // Make sure the file-based metadata on the TrackData is up to date.
+  data->filepath = path;
+  data->tags_hash = hash;
+  data->modified_at = {info.fdate, info.ftime};
+  data->is_tombstoned = false;
 
-  uint64_t time_per_old = 0;
-  if (num_old_tracks) {
-    time_per_old = (verify_end_time - start_time) / num_old_tracks;
-  }
-  uint64_t time_per_new = 0;
-  if (num_new_tracks) {
-    time_per_new = (end_time - verify_end_time) / num_new_tracks;
-  }
+  // Apply all the actual database changes as one atomic batch. This makes
+  // the whole 'new track' operation atomic, and also reduces the amount of
+  // lock contention when adding many tracks at once.
+  leveldb::WriteBatch batch;
+  dbIngestTagHashes(*tags, data->individual_tag_hashes, batch);
 
-  ESP_LOGI(
-      kTag,
-      "processed %lu old tracks and %lu new tracks in %llu seconds (%llums "
-      "per old, %llums per new)",
-      num_old_tracks, num_new_tracks, (end_time - start_time) / 1000000,
-      time_per_old / 1000, time_per_new / 1000);
+  dbCreateIndexesForTrack(*data, *tags, batch);
+  batch.Put(EncodeDataKey(data->id), EncodeDataValue(*data));
+  batch.Put(EncodeHashKey(data->tags_hash), EncodeHashValue(data->id));
+  batch.Put(EncodePathKey(path), TrackIdToBytes(data->id));
+
+  db_->Write(leveldb::WriteOptions(), &batch);
+}
+
+auto Database::indexingCompleteCallback() -> void {
+  update_tracker_.reset();
+  is_updating_ = false;
 }
 
 auto Database::isUpdating() -> bool {
   return is_updating_;
 }
 
-auto Database::dbMintNewTrackId() -> TrackId {
-  TrackId next_id = 1;
-  std::string val;
-  auto status = db_->Get(leveldb::ReadOptions(), kKeyTrackId, &val);
-  if (status.ok()) {
-    next_id = BytesToTrackId(val).value_or(next_id);
-  } else if (!status.IsNotFound()) {
-    // TODO(jacqueline): Handle this more.
-    ESP_LOGE(kTag, "failed to get next track id");
+auto Database::dbCalculateNextTrackId() -> void {
+  std::unique_ptr<leveldb::Iterator> it{
+      db_->NewIterator(leveldb::ReadOptions())};
+
+  // Track data entries are of the format 'D/trackid', where track ids are
+  // encoded as big-endian cbor types. They can therefore be compared through
+  // byte ordering, which means we can determine what the next id should be by
+  // looking at the larged track data record in the database.
+  std::string prefix = EncodeDataPrefix();
+  std::string prefixPlusOne = prefix;
+  prefixPlusOne[prefixPlusOne.size() - 1]++;
+
+  // Seek to just past the track data section.
+  it->Seek(prefixPlusOne);
+  if (!it->Valid()) {
+    next_track_id_ = 1;
+    return;
   }
 
-  if (!db_->Put(leveldb::WriteOptions(), kKeyTrackId,
-                TrackIdToBytes(next_id + 1))
-           .ok()) {
-    ESP_LOGE(kTag, "failed to write next track id");
+  // Go back to the last track data record.
+  it->Prev();
+  if (!it->Valid() || !it->key().starts_with(prefix)) {
+    next_track_id_ = 1;
+    return;
   }
 
-  return next_id;
-}
-
-auto Database::dbEntomb(TrackId id, uint64_t hash) -> void {
-  std::string key = EncodeHashKey(hash);
-  std::string val = EncodeHashValue(id);
-  if (!db_->Put(leveldb::WriteOptions(), key, val).ok()) {
-    ESP_LOGE(kTag, "failed to entomb #%llx (id #%lx)", hash, id);
+  // Parse the track id back out of the key.
+  std::span<const char> key{it->key().data(), it->key().size()};
+  auto id_part = key.subspan(prefix.size());
+  if (id_part.empty()) {
+    next_track_id_ = 1;
+    return;
   }
+
+  next_track_id_ = BytesToTrackId(id_part).value_or(0) + 1;
 }
 
-auto Database::dbPutTrackData(const TrackData& s) -> void {
-  std::string key = EncodeDataKey(s.id);
-  std::string val = EncodeDataValue(s);
-  if (!db_->Put(leveldb::WriteOptions(), key, val).ok()) {
-    ESP_LOGE(kTag, "failed to write data for #%lx", s.id);
-  }
+auto Database::dbMintNewTrackId() -> TrackId {
+  return next_track_id_++;
 }
 
-auto Database::dbGetTrackData(TrackId id) -> std::shared_ptr<TrackData> {
+auto Database::dbGetTrackData(leveldb::ReadOptions options, TrackId id)
+    -> std::shared_ptr<TrackData> {
   std::string key = EncodeDataKey(id);
   std::string raw_val;
-  if (!db_->Get(leveldb::ReadOptions(), key, &raw_val).ok()) {
+  if (!db_->Get(options, key, &raw_val).ok()) {
     ESP_LOGW(kTag, "no key found for #%lx", id);
     return {};
   }
   return ParseDataValue(raw_val);
 }
 
-auto Database::dbPutHash(const uint64_t& hash, TrackId i) -> void {
-  std::string key = EncodeHashKey(hash);
-  std::string val = EncodeHashValue(i);
-  if (!db_->Put(leveldb::WriteOptions(), key, val).ok()) {
-    ESP_LOGE(kTag, "failed to write hash for #%lx", i);
-  }
+auto Database::dbCreateIndexesForTrack(const Track& track,
+                                       leveldb::WriteBatch& batch) -> void {
+  dbCreateIndexesForTrack(track.data(), track.tags(), batch);
 }
 
-auto Database::dbGetHash(const uint64_t& hash) -> std::optional<TrackId> {
-  std::string key = EncodeHashKey(hash);
-  std::string raw_val;
-  if (!db_->Get(leveldb::ReadOptions(), key, &raw_val).ok()) {
-    ESP_LOGW(kTag, "no key found for hash #%llx", hash);
-    return {};
-  }
-  return ParseHashValue(raw_val);
-}
-
-auto Database::dbCreateIndexesForTrack(const Track& track) -> void {
+auto Database::dbCreateIndexesForTrack(const TrackData& data,
+                                       const TrackTags& tags,
+                                       leveldb::WriteBatch& batch) -> void {
   for (const IndexInfo& index : getIndexes()) {
-    leveldb::WriteBatch writes;
-    auto entries = Index(collator_, index, track);
+    auto entries = Index(collator_, index, data, tags);
     for (const auto& it : entries) {
-      writes.Put(EncodeIndexKey(it.first),
-                 {it.second.data(), it.second.size()});
+      batch.Put(EncodeIndexKey(it.first), {it.second.data(), it.second.size()});
     }
-    db_->Write(leveldb::WriteOptions(), &writes);
   }
 }
 
@@ -573,9 +585,8 @@ auto Database::dbRemoveIndexes(std::shared_ptr<TrackData> data) -> void {
   if (!tags) {
     return;
   }
-  Track track{data, tags};
   for (const IndexInfo& index : getIndexes()) {
-    auto entries = Index(collator_, index, track);
+    auto entries = Index(collator_, index, *data, *tags);
     for (auto it = entries.rbegin(); it != entries.rend(); it++) {
       auto key = EncodeIndexKey(it->first);
       auto status = db_->Delete(leveldb::WriteOptions{}, key);
@@ -602,16 +613,14 @@ auto Database::dbRemoveIndexes(std::shared_ptr<TrackData> data) -> void {
 }
 
 auto Database::dbIngestTagHashes(const TrackTags& tags,
-                                 std::pmr::unordered_map<Tag, uint64_t>& out)
-    -> void {
-  leveldb::WriteBatch batch{};
+                                 std::pmr::unordered_map<Tag, uint64_t>& out,
+                                 leveldb::WriteBatch& batch) -> void {
   for (const auto& tag : tags.allPresent()) {
     auto val = tags.get(tag);
     auto hash = tagHash(val);
     batch.Put(EncodeTagHashKey(hash), tagToString(val));
     out[tag] = hash;
   }
-  db_->Write(leveldb::WriteOptions{}, &batch);
 }
 
 auto Database::dbRecoverTagsFromHashes(