RocksDB: Allow Level-Style Compaction to Place Files in Different Paths

Summary:
Allow Level-style compaction to place files in different paths
This diff provides the code for task 4854591. We now support level-compaction
to place files in different paths by specifying  them in db_paths  along with
the minimum level for files to store in that path.

Test Plan: ManualLevelCompactionOutputPathId in db_test.cc

Reviewers: yhchiang, MarkCallaghan, dhruba, yoshinorim, sdong

Reviewed By: sdong

Subscribers: yoshinorim, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D29799

HISTORY.md

@@ -14,9 +14,13 @@
 ### Public API changes
 * New API to create a checkpoint added. Given a directory name, creates a new
   database which is an image of the existing database.
-*New API LinkFile added to Env. If you implement your own Env class, an
+* New API LinkFile added to Env. If you implement your own Env class, an
- implementation of the API LinkFile will have to be provided.
+  implementation of the API LinkFile will have to be provided.
 * MemTableRep takes MemTableAllocator instead of Arena
+* We now allow level-compaction to place files in different paths by
+  specifying them in db_paths along with the target_size.
+  Lower numbered levels will be placed earlier in the db_paths and higher
+  numbered levels will be placed later in the db_paths vector.
 
 ### Improvements
 * RocksDBLite library now becomes smaller and will be compiled with -fno-exceptions flag.

db/compaction_picker.cc

@@ -769,6 +769,44 @@ Compaction* LevelCompactionPicker::PickCompaction(
   return c;
 }
 
+/*
+ * Find the optimal path to place a file
+ * Given a level, finds the path where levels up to it will fit in levels
+ * up to and including this path
+ */
+uint32_t LevelCompactionPicker::GetPathId(
+    const ImmutableCFOptions& ioptions,
+    const MutableCFOptions& mutable_cf_options, int level) {
+  uint32_t p = 0;
+  assert(!ioptions.db_paths.empty());
+
+  // size remaining in the most recent path
+  uint64_t current_path_size = ioptions.db_paths[0].target_size;
+
+  uint64_t level_size;
+  int cur_level = 0;
+
+  level_size = mutable_cf_options.max_bytes_for_level_base;
+
+  // Last path is the fallback
+  while (p < ioptions.db_paths.size() - 1) {
+    if (level_size <= current_path_size) {
+      if (cur_level == level) {
+        // Does desired level fit in this path?
+        return p;
+      } else {
+        current_path_size -= level_size;
+        level_size *= mutable_cf_options.max_bytes_for_level_multiplier;
+        cur_level++;
+        continue;
+      }
+    }
+    p++;
+    current_path_size = ioptions.db_paths[p].target_size;
+  }
+  return p;
+}
+
 Compaction* LevelCompactionPicker::PickCompactionBySize(
     const MutableCFOptions& mutable_cf_options, VersionStorageInfo* vstorage,
     int level, double score) {
@@ -786,7 +824,8 @@ Compaction* LevelCompactionPicker::PickCompactionBySize(
   assert(level + 1 < NumberLevels());
   c = new Compaction(vstorage->num_levels(), level, level + 1,
                      mutable_cf_options.MaxFileSizeForLevel(level + 1),
-                     mutable_cf_options.MaxGrandParentOverlapBytes(level), 0,
+                     mutable_cf_options.MaxGrandParentOverlapBytes(level),
+                     GetPathId(ioptions_, mutable_cf_options, level + 1),
                      GetCompressionType(ioptions_, level + 1));
   c->score_ = score;
 
@@ -960,6 +999,7 @@ uint32_t UniversalCompactionPicker::GetPathId(
   uint64_t future_size = file_size *
     (100 - ioptions.compaction_options_universal.size_ratio) / 100;
   uint32_t p = 0;
+  assert(!ioptions.db_paths.empty());
   for (; p < ioptions.db_paths.size() - 1; p++) {
     uint64_t target_size = ioptions.db_paths[p].target_size;
     if (target_size > file_size &&

db/compaction_picker.h

@@ -188,6 +188,11 @@ class LevelCompactionPicker : public CompactionPicker {
   virtual bool NeedsCompaction(const VersionStorageInfo* vstorage) const
       override;
 
+  // Pick a path ID to place a newly generated file, with its level
+  static uint32_t GetPathId(const ImmutableCFOptions& ioptions,
+                            const MutableCFOptions& mutable_cf_options,
+                            int level);
+
  private:
   // For the specfied level, pick a compaction.
   // Returns nullptr if there is no compaction to be done.

db/compaction_picker_test.cc

@@ -4,6 +4,7 @@
 //  of patent rights can be found in the PATENTS file in the same directory.
 
 #include "db/compaction_picker.h"
+#include <limits>
 #include <string>
 #include "util/logging.h"
 #include "util/testharness.h"
@@ -47,6 +48,8 @@ class CompactionPickerTest {
     fifo_options_.max_table_files_size = 1;
     mutable_cf_options_.RefreshDerivedOptions(ioptions_);
     size_being_compacted_.resize(options_.num_levels);
+    ioptions_.db_paths.emplace_back("dummy",
+                                    std::numeric_limits<uint64_t>::max());
   }
 
   ~CompactionPickerTest() {

db/db_impl.cc

@@ -67,6 +67,7 @@
 #include "util/build_version.h"
 #include "util/coding.h"
 #include "util/db_info_dumper.h"
+#include "util/file_util.h"
 #include "util/hash_skiplist_rep.h"
 #include "util/hash_linklist_rep.h"
 #include "util/logging.h"
@@ -2059,10 +2060,31 @@ Status DBImpl::BackgroundCompaction(bool* madeProgress, JobContext* job_context,
     // Move file to next level
     assert(c->num_input_files(0) == 1);
     FileMetaData* f = c->input(0, 0);
+    FileMetaData ftemp;
+    uint64_t fdnum = f->fd.GetNumber();
+    uint32_t fdpath = f->fd.GetPathId();
     c->edit()->DeleteFile(c->level(), f->fd.GetNumber());
-    c->edit()->AddFile(c->level() + 1, f->fd.GetNumber(), f->fd.GetPathId(),
+    // Need to move file if file is to be stored in a new path
-                       f->fd.GetFileSize(), f->smallest, f->largest,
+    if (c->GetOutputPathId() != f->fd.GetPathId()) {
-                       f->smallest_seqno, f->largest_seqno);
+      fdnum = versions_->NewFileNumber();
+      std::string source = TableFileName(db_options_.db_paths,
+                                         f->fd.GetNumber(), f->fd.GetPathId());
+      std::string destination =
+          TableFileName(db_options_.db_paths, fdnum, c->GetOutputPathId());
+      Status s = CopyFile(env_, source, destination, 0);
+      if (s.ok()) {
+        fdpath = c->GetOutputPathId();
+      } else {
+        fdnum = f->fd.GetNumber();
+        if (!s.IsShutdownInProgress()) {
+          Log(InfoLogLevel::WARN_LEVEL, db_options_.info_log,
+              "Compaction error: %s", s.ToString().c_str());
+        }
+      }
+    }
+    c->edit()->AddFile(c->level() + 1, fdnum, fdpath, f->fd.GetFileSize(),
+                       f->smallest, f->largest, f->smallest_seqno,
+                       f->largest_seqno);
     status = versions_->LogAndApply(c->column_family_data(),
                                     *c->mutable_cf_options(),
                                     c->edit(), &mutex_, db_directory_.get());
@@ -3519,18 +3541,20 @@ Status DB::Open(const DBOptions& db_options, const std::string& dbname,
   if (!s.ok()) {
     return s;
   }
+
   if (db_options.db_paths.size() > 1) {
     for (auto& cfd : column_families) {
-      if (cfd.options.compaction_style != kCompactionStyleUniversal) {
+      if ((cfd.options.compaction_style != kCompactionStyleUniversal) &&
+          (cfd.options.compaction_style != kCompactionStyleLevel)) {
         return Status::NotSupported(
             "More than one DB paths are only supported in "
-            "universal compaction style. ");
+            "universal and level compaction styles. ");
       }
     }
 
     if (db_options.db_paths.size() > 4) {
       return Status::NotSupported(
-        "More than four DB paths are not supported yet. ");
+          "More than four DB paths are not supported yet. ");
     }
   }
 

db/db_test.cc

@@ -1004,6 +1004,12 @@ class DBTest {
     return size;
   }
 
+  void Compact(int cf, const Slice& start, const Slice& limit,
+               uint32_t target_path_id) {
+    ASSERT_OK(db_->CompactRange(handles_[cf], &start, &limit, false, -1,
+                                target_path_id));
+  }
+
   void Compact(int cf, const Slice& start, const Slice& limit) {
     ASSERT_OK(db_->CompactRange(handles_[cf], &start, &limit));
   }
@@ -4087,6 +4093,233 @@ TEST(DBTest, UniversalCompactionSecondPathRatio) {
   Destroy(options);
 }
 
+TEST(DBTest, LevelCompactionThirdPath) {
+  Options options;
+  options.db_paths.emplace_back(dbname_, 500 * 1024);
+  options.db_paths.emplace_back(dbname_ + "_2", 4 * 1024 * 1024);
+  options.db_paths.emplace_back(dbname_ + "_3", 1024 * 1024 * 1024);
+  options.compaction_style = kCompactionStyleLevel;
+  options.write_buffer_size = 100 << 10;  // 100KB
+  options.level0_file_num_compaction_trigger = 2;
+  options.num_levels = 4;
+  options.max_bytes_for_level_base = 400 * 1024;
+  //  options = CurrentOptions(options);
+
+  std::vector<std::string> filenames;
+  env_->GetChildren(options.db_paths[1].path, &filenames);
+  // Delete archival files.
+  for (size_t i = 0; i < filenames.size(); ++i) {
+    env_->DeleteFile(options.db_paths[1].path + "/" + filenames[i]);
+  }
+  env_->DeleteDir(options.db_paths[1].path);
+  Reopen(options);
+
+  Random rnd(301);
+  int key_idx = 0;
+
+  // First three 110KB files are not going to second path.
+  // After that, (100K, 200K)
+  for (int num = 0; num < 3; num++) {
+    GenerateNewFile(&rnd, &key_idx);
+  }
+
+  // Another 110KB triggers a compaction to 400K file to fill up first path
+  GenerateNewFile(&rnd, &key_idx);
+  ASSERT_EQ(3, GetSstFileCount(options.db_paths[1].path));
+
+  // (1, 4)
+  GenerateNewFile(&rnd, &key_idx);
+  ASSERT_EQ("1,4", FilesPerLevel(0));
+  ASSERT_EQ(4, GetSstFileCount(options.db_paths[1].path));
+  ASSERT_EQ(1, GetSstFileCount(dbname_));
+
+  // (1, 4, 1)
+  GenerateNewFile(&rnd, &key_idx);
+  ASSERT_EQ("1,4,1", FilesPerLevel(0));
+  ASSERT_EQ(1, GetSstFileCount(options.db_paths[2].path));
+  ASSERT_EQ(4, GetSstFileCount(options.db_paths[1].path));
+  ASSERT_EQ(1, GetSstFileCount(dbname_));
+
+  // (1, 4, 2)
+  GenerateNewFile(&rnd, &key_idx);
+  ASSERT_EQ("1,4,2", FilesPerLevel(0));
+  ASSERT_EQ(2, GetSstFileCount(options.db_paths[2].path));
+  ASSERT_EQ(4, GetSstFileCount(options.db_paths[1].path));
+  ASSERT_EQ(1, GetSstFileCount(dbname_));
+
+  // (1, 4, 3)
+  GenerateNewFile(&rnd, &key_idx);
+  ASSERT_EQ("1,4,3", FilesPerLevel(0));
+  ASSERT_EQ(3, GetSstFileCount(options.db_paths[2].path));
+  ASSERT_EQ(4, GetSstFileCount(options.db_paths[1].path));
+  ASSERT_EQ(1, GetSstFileCount(dbname_));
+
+  // (1, 4, 4)
+  GenerateNewFile(&rnd, &key_idx);
+  ASSERT_EQ("1,4,4", FilesPerLevel(0));
+  ASSERT_EQ(4, GetSstFileCount(options.db_paths[2].path));
+  ASSERT_EQ(4, GetSstFileCount(options.db_paths[1].path));
+  ASSERT_EQ(1, GetSstFileCount(dbname_));
+
+  // (1, 4, 5)
+  GenerateNewFile(&rnd, &key_idx);
+  ASSERT_EQ("1,4,5", FilesPerLevel(0));
+  ASSERT_EQ(5, GetSstFileCount(options.db_paths[2].path));
+  ASSERT_EQ(4, GetSstFileCount(options.db_paths[1].path));
+  ASSERT_EQ(1, GetSstFileCount(dbname_));
+
+  // (1, 4, 6)
+  GenerateNewFile(&rnd, &key_idx);
+  ASSERT_EQ("1,4,6", FilesPerLevel(0));
+  ASSERT_EQ(6, GetSstFileCount(options.db_paths[2].path));
+  ASSERT_EQ(4, GetSstFileCount(options.db_paths[1].path));
+  ASSERT_EQ(1, GetSstFileCount(dbname_));
+
+  // (1, 4, 7)
+  GenerateNewFile(&rnd, &key_idx);
+  ASSERT_EQ("1,4,7", FilesPerLevel(0));
+  ASSERT_EQ(7, GetSstFileCount(options.db_paths[2].path));
+  ASSERT_EQ(4, GetSstFileCount(options.db_paths[1].path));
+  ASSERT_EQ(1, GetSstFileCount(dbname_));
+
+  // (1, 4, 8)
+  GenerateNewFile(&rnd, &key_idx);
+  ASSERT_EQ("1,4,8", FilesPerLevel(0));
+  ASSERT_EQ(8, GetSstFileCount(options.db_paths[2].path));
+  ASSERT_EQ(4, GetSstFileCount(options.db_paths[1].path));
+  ASSERT_EQ(1, GetSstFileCount(dbname_));
+
+  for (int i = 0; i < key_idx; i++) {
+    auto v = Get(Key(i));
+    ASSERT_NE(v, "NOT_FOUND");
+    ASSERT_TRUE(v.size() == 1 || v.size() == 10000);
+  }
+
+  Reopen(options);
+
+  for (int i = 0; i < key_idx; i++) {
+    auto v = Get(Key(i));
+    ASSERT_NE(v, "NOT_FOUND");
+    ASSERT_TRUE(v.size() == 1 || v.size() == 10000);
+  }
+
+  Destroy(options);
+}
+
+TEST(DBTest, LevelCompactionPathUse) {
+  Options options;
+  options.db_paths.emplace_back(dbname_, 500 * 1024);
+  options.db_paths.emplace_back(dbname_ + "_2", 4 * 1024 * 1024);
+  options.db_paths.emplace_back(dbname_ + "_3", 1024 * 1024 * 1024);
+  options.compaction_style = kCompactionStyleLevel;
+  options.write_buffer_size = 100 << 10;  // 100KB
+  options.level0_file_num_compaction_trigger = 2;
+  options.num_levels = 4;
+  options.max_bytes_for_level_base = 400 * 1024;
+  //  options = CurrentOptions(options);
+
+  std::vector<std::string> filenames;
+  env_->GetChildren(options.db_paths[1].path, &filenames);
+  // Delete archival files.
+  for (size_t i = 0; i < filenames.size(); ++i) {
+    env_->DeleteFile(options.db_paths[1].path + "/" + filenames[i]);
+  }
+  env_->DeleteDir(options.db_paths[1].path);
+  Reopen(options);
+
+  Random rnd(301);
+  int key_idx = 0;
+
+  // Always gets compacted into 1 Level1 file,
+  // 0/1 Level 0 file
+  for (int num = 0; num < 3; num++) {
+    key_idx = 0;
+    GenerateNewFile(&rnd, &key_idx);
+  }
+
+  key_idx = 0;
+  GenerateNewFile(&rnd, &key_idx);
+  ASSERT_EQ(1, GetSstFileCount(options.db_paths[1].path));
+
+  key_idx = 0;
+  GenerateNewFile(&rnd, &key_idx);
+  ASSERT_EQ("1,1", FilesPerLevel(0));
+  ASSERT_EQ(1, GetSstFileCount(options.db_paths[1].path));
+  ASSERT_EQ(1, GetSstFileCount(dbname_));
+
+  key_idx = 0;
+  GenerateNewFile(&rnd, &key_idx);
+  ASSERT_EQ("0,1", FilesPerLevel(0));
+  ASSERT_EQ(0, GetSstFileCount(options.db_paths[2].path));
+  ASSERT_EQ(1, GetSstFileCount(options.db_paths[1].path));
+  ASSERT_EQ(0, GetSstFileCount(dbname_));
+
+  key_idx = 0;
+  GenerateNewFile(&rnd, &key_idx);
+  ASSERT_EQ("1,1", FilesPerLevel(0));
+  ASSERT_EQ(0, GetSstFileCount(options.db_paths[2].path));
+  ASSERT_EQ(1, GetSstFileCount(options.db_paths[1].path));
+  ASSERT_EQ(1, GetSstFileCount(dbname_));
+
+  key_idx = 0;
+  GenerateNewFile(&rnd, &key_idx);
+  ASSERT_EQ("0,1", FilesPerLevel(0));
+  ASSERT_EQ(0, GetSstFileCount(options.db_paths[2].path));
+  ASSERT_EQ(1, GetSstFileCount(options.db_paths[1].path));
+  ASSERT_EQ(0, GetSstFileCount(dbname_));
+
+  key_idx = 0;
+  GenerateNewFile(&rnd, &key_idx);
+  ASSERT_EQ("1,1", FilesPerLevel(0));
+  ASSERT_EQ(0, GetSstFileCount(options.db_paths[2].path));
+  ASSERT_EQ(1, GetSstFileCount(options.db_paths[1].path));
+  ASSERT_EQ(1, GetSstFileCount(dbname_));
+
+  key_idx = 0;
+  GenerateNewFile(&rnd, &key_idx);
+  ASSERT_EQ("0,1", FilesPerLevel(0));
+  ASSERT_EQ(0, GetSstFileCount(options.db_paths[2].path));
+  ASSERT_EQ(1, GetSstFileCount(options.db_paths[1].path));
+  ASSERT_EQ(0, GetSstFileCount(dbname_));
+
+  key_idx = 0;
+  GenerateNewFile(&rnd, &key_idx);
+  ASSERT_EQ("1,1", FilesPerLevel(0));
+  ASSERT_EQ(0, GetSstFileCount(options.db_paths[2].path));
+  ASSERT_EQ(1, GetSstFileCount(options.db_paths[1].path));
+  ASSERT_EQ(1, GetSstFileCount(dbname_));
+
+  key_idx = 0;
+  GenerateNewFile(&rnd, &key_idx);
+  ASSERT_EQ("0,1", FilesPerLevel(0));
+  ASSERT_EQ(0, GetSstFileCount(options.db_paths[2].path));
+  ASSERT_EQ(1, GetSstFileCount(options.db_paths[1].path));
+  ASSERT_EQ(0, GetSstFileCount(dbname_));
+
+  key_idx = 0;
+  GenerateNewFile(&rnd, &key_idx);
+  ASSERT_EQ("1,1", FilesPerLevel(0));
+  ASSERT_EQ(0, GetSstFileCount(options.db_paths[2].path));
+  ASSERT_EQ(1, GetSstFileCount(options.db_paths[1].path));
+  ASSERT_EQ(1, GetSstFileCount(dbname_));
+
+  for (int i = 0; i < key_idx; i++) {
+    auto v = Get(Key(i));
+    ASSERT_NE(v, "NOT_FOUND");
+    ASSERT_TRUE(v.size() == 1 || v.size() == 10000);
+  }
+
+  Reopen(options);
+
+  for (int i = 0; i < key_idx; i++) {
+    auto v = Get(Key(i));
+    ASSERT_NE(v, "NOT_FOUND");
+    ASSERT_TRUE(v.size() == 1 || v.size() == 10000);
+  }
+
+  Destroy(options);
+}
+
 TEST(DBTest, UniversalCompactionFourPaths) {
   Options options;
   options.db_paths.emplace_back(dbname_, 300 * 1024);
@@ -5953,6 +6186,75 @@ TEST(DBTest, ManualCompactionOutputPathId) {
                   .IsInvalidArgument());
 }
 
+TEST(DBTest, ManualLevelCompactionOutputPathId) {
+  Options options = CurrentOptions();
+  options.db_paths.emplace_back(dbname_ + "_2", 2 * 10485760);
+  options.db_paths.emplace_back(dbname_ + "_3", 100 * 10485760);
+  options.db_paths.emplace_back(dbname_ + "_4", 120 * 10485760);
+  options.max_background_flushes = 1;
+  CreateAndReopenWithCF({"pikachu"}, options);
+  ASSERT_EQ(dbfull()->MaxMemCompactionLevel(), 2)
+      << "Need to update this test to match kMaxMemCompactLevel";
+
+  // iter - 0 with 7 levels
+  // iter - 1 with 3 levels
+  for (int iter = 0; iter < 2; ++iter) {
+    MakeTables(3, "p", "q", 1);
+    ASSERT_EQ("3", FilesPerLevel(1));
+    ASSERT_EQ(3, GetSstFileCount(options.db_paths[0].path));
+    ASSERT_EQ(0, GetSstFileCount(dbname_));
+
+    // Compaction range falls before files
+    Compact(1, "", "c");
+    ASSERT_EQ("3", FilesPerLevel(1));
+
+    // Compaction range falls after files
+    Compact(1, "r", "z");
+    ASSERT_EQ("3", FilesPerLevel(1));
+
+    // Compaction range overlaps files
+    Compact(1, "p1", "p9", 1);
+    ASSERT_EQ("0,1", FilesPerLevel(1));
+    ASSERT_EQ(1, GetSstFileCount(options.db_paths[1].path));
+    ASSERT_EQ(0, GetSstFileCount(options.db_paths[0].path));
+    ASSERT_EQ(0, GetSstFileCount(dbname_));
+
+    // Populate a different range
+    MakeTables(3, "c", "e", 1);
+    ASSERT_EQ("3,1", FilesPerLevel(1));
+
+    // Compact just the new range
+    Compact(1, "b", "f", 1);
+    ASSERT_EQ("0,2", FilesPerLevel(1));
+    ASSERT_EQ(2, GetSstFileCount(options.db_paths[1].path));
+    ASSERT_EQ(0, GetSstFileCount(options.db_paths[0].path));
+    ASSERT_EQ(0, GetSstFileCount(dbname_));
+
+    // Compact all
+    MakeTables(1, "a", "z", 1);
+    ASSERT_EQ("1,2", FilesPerLevel(1));
+    ASSERT_EQ(2, GetSstFileCount(options.db_paths[1].path));
+    ASSERT_EQ(1, GetSstFileCount(options.db_paths[0].path));
+    db_->CompactRange(handles_[1], nullptr, nullptr, false, 1, 1);
+    ASSERT_EQ("0,1", FilesPerLevel(1));
+    ASSERT_EQ(1, GetSstFileCount(options.db_paths[1].path));
+    ASSERT_EQ(0, GetSstFileCount(options.db_paths[0].path));
+    ASSERT_EQ(0, GetSstFileCount(dbname_));
+
+    if (iter == 0) {
+      DestroyAndReopen(options);
+      options = CurrentOptions();
+      options.db_paths.emplace_back(dbname_ + "_2", 2 * 10485760);
+      options.db_paths.emplace_back(dbname_ + "_3", 100 * 10485760);
+      options.db_paths.emplace_back(dbname_ + "_4", 120 * 10485760);
+      options.max_background_flushes = 1;
+      options.num_levels = 3;
+      options.create_if_missing = true;
+      CreateAndReopenWithCF({"pikachu"}, options);
+    }
+  }
+}
+
 TEST(DBTest, DBOpen_Options) {
   Options options = CurrentOptions();
   std::string dbname = test::TmpDir(env_) + "/db_options_test";

db/flush_job.cc

@@ -40,6 +40,7 @@
 #include "table/table_builder.h"
 #include "table/two_level_iterator.h"
 #include "util/coding.h"
+#include "util/file_util.h"
 #include "util/logging.h"
 #include "util/log_buffer.h"
 #include "util/mutexlock.h"
@@ -194,6 +195,12 @@ Status FlushJob::WriteLevel0Table(const autovector<MemTable*>& mems,
         cfd_->ioptions()->compaction_style == kCompactionStyleLevel) {
       level = base->storage_info()->PickLevelForMemTableOutput(
           mutable_cf_options_, min_user_key, max_user_key);
+      // If level does not match path id, reset level back to 0
+      uint32_t fdpath = LevelCompactionPicker::GetPathId(
+          *cfd_->ioptions(), mutable_cf_options_, level);
+      if (fdpath != 0) {
+        level = 0;
+      }
     }
     edit->AddFile(level, meta.fd.GetNumber(), meta.fd.GetPathId(),
                   meta.fd.GetFileSize(), meta.smallest, meta.largest,