Adding upstream version 18.2.2.upstream/18.2.2

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1450 insertions, 0 deletions

diff --git a/src/rocksdb/db/compaction/compaction_picker_universal.cc b/src/rocksdb/db/compaction/compaction_picker_universal.cc
new file mode 100644
index 000000000..376e4f60f
--- /dev/null
+++ b/src/rocksdb/db/compaction/compaction_picker_universal.cc
@@ -0,0 +1,1450 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "db/compaction/compaction_picker_universal.h"
+#ifndef ROCKSDB_LITE
+
+#include <cinttypes>
+#include <limits>
+#include <queue>
+#include <string>
+#include <utility>
+
+#include "db/column_family.h"
+#include "file/filename.h"
+#include "logging/log_buffer.h"
+#include "logging/logging.h"
+#include "monitoring/statistics.h"
+#include "test_util/sync_point.h"
+#include "util/random.h"
+#include "util/string_util.h"
+
+namespace ROCKSDB_NAMESPACE {
+namespace {
+// A helper class that form universal compactions. The class is used by
+// UniversalCompactionPicker::PickCompaction().
+// The usage is to create the class, and get the compaction object by calling
+// PickCompaction().
+class UniversalCompactionBuilder {
+ public:
+  UniversalCompactionBuilder(
+      const ImmutableOptions& ioptions, const InternalKeyComparator* icmp,
+      const std::string& cf_name, const MutableCFOptions& mutable_cf_options,
+      const MutableDBOptions& mutable_db_options, VersionStorageInfo* vstorage,
+      UniversalCompactionPicker* picker, LogBuffer* log_buffer)
+      : ioptions_(ioptions),
+        icmp_(icmp),
+        cf_name_(cf_name),
+        mutable_cf_options_(mutable_cf_options),
+        mutable_db_options_(mutable_db_options),
+        vstorage_(vstorage),
+        picker_(picker),
+        log_buffer_(log_buffer) {}
+
+  // Form and return the compaction object. The caller owns return object.
+  Compaction* PickCompaction();
+
+ private:
+  struct SortedRun {
+    SortedRun(int _level, FileMetaData* _file, uint64_t _size,
+              uint64_t _compensated_file_size, bool _being_compacted)
+        : level(_level),
+          file(_file),
+          size(_size),
+          compensated_file_size(_compensated_file_size),
+          being_compacted(_being_compacted) {
+      assert(compensated_file_size > 0);
+      assert(level != 0 || file != nullptr);
+    }
+
+    void Dump(char* out_buf, size_t out_buf_size,
+              bool print_path = false) const;
+
+    // sorted_run_count is added into the string to print
+    void DumpSizeInfo(char* out_buf, size_t out_buf_size,
+                      size_t sorted_run_count) const;
+
+    int level;
+    // `file` Will be null for level > 0. For level = 0, the sorted run is
+    // for this file.
+    FileMetaData* file;
+    // For level > 0, `size` and `compensated_file_size` are sum of sizes all
+    // files in the level. `being_compacted` should be the same for all files
+    // in a non-zero level. Use the value here.
+    uint64_t size;
+    uint64_t compensated_file_size;
+    bool being_compacted;
+  };
+
+  // Pick Universal compaction to limit read amplification
+  Compaction* PickCompactionToReduceSortedRuns(
+      unsigned int ratio, unsigned int max_number_of_files_to_compact);
+
+  // Pick Universal compaction to limit space amplification.
+  Compaction* PickCompactionToReduceSizeAmp();
+
+  // Try to pick incremental compaction to reduce space amplification.
+  // It will return null if it cannot find a fanout within the threshold.
+  // Fanout is defined as
+  //    total size of files to compact at output level
+  //  --------------------------------------------------
+  //    total size of files to compact at other levels
+  Compaction* PickIncrementalForReduceSizeAmp(double fanout_threshold);
+
+  Compaction* PickDeleteTriggeredCompaction();
+
+  // Form a compaction from the sorted run indicated by start_index to the
+  // oldest sorted run.
+  // The caller is responsible for making sure that those files are not in
+  // compaction.
+  Compaction* PickCompactionToOldest(size_t start_index,
+                                     CompactionReason compaction_reason);
+
+  Compaction* PickCompactionWithSortedRunRange(
+      size_t start_index, size_t end_index, CompactionReason compaction_reason);
+
+  // Try to pick periodic compaction. The caller should only call it
+  // if there is at least one file marked for periodic compaction.
+  // null will be returned if no such a compaction can be formed
+  // because some files are being compacted.
+  Compaction* PickPeriodicCompaction();
+
+  // Used in universal compaction when the allow_trivial_move
+  // option is set. Checks whether there are any overlapping files
+  // in the input. Returns true if the input files are non
+  // overlapping.
+  bool IsInputFilesNonOverlapping(Compaction* c);
+
+  uint64_t GetMaxOverlappingBytes() const;
+
+  const ImmutableOptions& ioptions_;
+  const InternalKeyComparator* icmp_;
+  double score_;
+  std::vector<SortedRun> sorted_runs_;
+  const std::string& cf_name_;
+  const MutableCFOptions& mutable_cf_options_;
+  const MutableDBOptions& mutable_db_options_;
+  VersionStorageInfo* vstorage_;
+  UniversalCompactionPicker* picker_;
+  LogBuffer* log_buffer_;
+
+  static std::vector<SortedRun> CalculateSortedRuns(
+      const VersionStorageInfo& vstorage);
+
+  // Pick a path ID to place a newly generated file, with its estimated file
+  // size.
+  static uint32_t GetPathId(const ImmutableCFOptions& ioptions,
+                            const MutableCFOptions& mutable_cf_options,
+                            uint64_t file_size);
+};
+
+// Used in universal compaction when trivial move is enabled.
+// This structure is used for the construction of min heap
+// that contains the file meta data, the level of the file
+// and the index of the file in that level
+
+struct InputFileInfo {
+  InputFileInfo() : f(nullptr), level(0), index(0) {}
+
+  FileMetaData* f;
+  size_t level;
+  size_t index;
+};
+
+// Used in universal compaction when trivial move is enabled.
+// This comparator is used for the construction of min heap
+// based on the smallest key of the file.
+struct SmallestKeyHeapComparator {
+  explicit SmallestKeyHeapComparator(const Comparator* ucmp) { ucmp_ = ucmp; }
+
+  bool operator()(InputFileInfo i1, InputFileInfo i2) const {
+    return (ucmp_->CompareWithoutTimestamp(i1.f->smallest.user_key(),
+                                           i2.f->smallest.user_key()) > 0);
+  }
+
+ private:
+  const Comparator* ucmp_;
+};
+
+using SmallestKeyHeap =
+    std::priority_queue<InputFileInfo, std::vector<InputFileInfo>,
+                        SmallestKeyHeapComparator>;
+
+// This function creates the heap that is used to find if the files are
+// overlapping during universal compaction when the allow_trivial_move
+// is set.
+SmallestKeyHeap create_level_heap(Compaction* c, const Comparator* ucmp) {
+  SmallestKeyHeap smallest_key_priority_q =
+      SmallestKeyHeap(SmallestKeyHeapComparator(ucmp));
+
+  InputFileInfo input_file;
+
+  for (size_t l = 0; l < c->num_input_levels(); l++) {
+    if (c->num_input_files(l) != 0) {
+      if (l == 0 && c->start_level() == 0) {
+        for (size_t i = 0; i < c->num_input_files(0); i++) {
+          input_file.f = c->input(0, i);
+          input_file.level = 0;
+          input_file.index = i;
+          smallest_key_priority_q.push(std::move(input_file));
+        }
+      } else {
+        input_file.f = c->input(l, 0);
+        input_file.level = l;
+        input_file.index = 0;
+        smallest_key_priority_q.push(std::move(input_file));
+      }
+    }
+  }
+  return smallest_key_priority_q;
+}
+
+#ifndef NDEBUG
+// smallest_seqno and largest_seqno are set iff. `files` is not empty.
+void GetSmallestLargestSeqno(const std::vector<FileMetaData*>& files,
+                             SequenceNumber* smallest_seqno,
+                             SequenceNumber* largest_seqno) {
+  bool is_first = true;
+  for (FileMetaData* f : files) {
+    assert(f->fd.smallest_seqno <= f->fd.largest_seqno);
+    if (is_first) {
+      is_first = false;
+      *smallest_seqno = f->fd.smallest_seqno;
+      *largest_seqno = f->fd.largest_seqno;
+    } else {
+      if (f->fd.smallest_seqno < *smallest_seqno) {
+        *smallest_seqno = f->fd.smallest_seqno;
+      }
+      if (f->fd.largest_seqno > *largest_seqno) {
+        *largest_seqno = f->fd.largest_seqno;
+      }
+    }
+  }
+}
+#endif
+}  // namespace
+
+// Algorithm that checks to see if there are any overlapping
+// files in the input
+bool UniversalCompactionBuilder::IsInputFilesNonOverlapping(Compaction* c) {
+  auto comparator = icmp_->user_comparator();
+  int first_iter = 1;
+
+  InputFileInfo prev, curr, next;
+
+  SmallestKeyHeap smallest_key_priority_q =
+      create_level_heap(c, icmp_->user_comparator());
+
+  while (!smallest_key_priority_q.empty()) {
+    curr = smallest_key_priority_q.top();
+    smallest_key_priority_q.pop();
+
+    if (first_iter) {
+      prev = curr;
+      first_iter = 0;
+    } else {
+      if (comparator->CompareWithoutTimestamp(
+              prev.f->largest.user_key(), curr.f->smallest.user_key()) >= 0) {
+        // found overlapping files, return false
+        return false;
+      }
+      assert(comparator->CompareWithoutTimestamp(
+                 curr.f->largest.user_key(), prev.f->largest.user_key()) > 0);
+      prev = curr;
+    }
+
+    next.f = nullptr;
+
+    if (c->level(curr.level) != 0 &&
+        curr.index < c->num_input_files(curr.level) - 1) {
+      next.f = c->input(curr.level, curr.index + 1);
+      next.level = curr.level;
+      next.index = curr.index + 1;
+    }
+
+    if (next.f) {
+      smallest_key_priority_q.push(std::move(next));
+    }
+  }
+  return true;
+}
+
+bool UniversalCompactionPicker::NeedsCompaction(
+    const VersionStorageInfo* vstorage) const {
+  const int kLevel0 = 0;
+  if (vstorage->CompactionScore(kLevel0) >= 1) {
+    return true;
+  }
+  if (!vstorage->FilesMarkedForPeriodicCompaction().empty()) {
+    return true;
+  }
+  if (!vstorage->FilesMarkedForCompaction().empty()) {
+    return true;
+  }
+  return false;
+}
+
+Compaction* UniversalCompactionPicker::PickCompaction(
+    const std::string& cf_name, const MutableCFOptions& mutable_cf_options,
+    const MutableDBOptions& mutable_db_options, VersionStorageInfo* vstorage,
+    LogBuffer* log_buffer, SequenceNumber /* earliest_memtable_seqno */) {
+  UniversalCompactionBuilder builder(ioptions_, icmp_, cf_name,
+                                     mutable_cf_options, mutable_db_options,
+                                     vstorage, this, log_buffer);
+  return builder.PickCompaction();
+}
+
+void UniversalCompactionBuilder::SortedRun::Dump(char* out_buf,
+                                                 size_t out_buf_size,
+                                                 bool print_path) const {
+  if (level == 0) {
+    assert(file != nullptr);
+    if (file->fd.GetPathId() == 0 || !print_path) {
+      snprintf(out_buf, out_buf_size, "file %" PRIu64, file->fd.GetNumber());
+    } else {
+      snprintf(out_buf, out_buf_size,
+               "file %" PRIu64
+               "(path "
+               "%" PRIu32 ")",
+               file->fd.GetNumber(), file->fd.GetPathId());
+    }
+  } else {
+    snprintf(out_buf, out_buf_size, "level %d", level);
+  }
+}
+
+void UniversalCompactionBuilder::SortedRun::DumpSizeInfo(
+    char* out_buf, size_t out_buf_size, size_t sorted_run_count) const {
+  if (level == 0) {
+    assert(file != nullptr);
+    snprintf(out_buf, out_buf_size,
+             "file %" PRIu64 "[%" ROCKSDB_PRIszt
+             "] "
+             "with size %" PRIu64 " (compensated size %" PRIu64 ")",
+             file->fd.GetNumber(), sorted_run_count, file->fd.GetFileSize(),
+             file->compensated_file_size);
+  } else {
+    snprintf(out_buf, out_buf_size,
+             "level %d[%" ROCKSDB_PRIszt
+             "] "
+             "with size %" PRIu64 " (compensated size %" PRIu64 ")",
+             level, sorted_run_count, size, compensated_file_size);
+  }
+}
+
+std::vector<UniversalCompactionBuilder::SortedRun>
+UniversalCompactionBuilder::CalculateSortedRuns(
+    const VersionStorageInfo& vstorage) {
+  std::vector<UniversalCompactionBuilder::SortedRun> ret;
+  for (FileMetaData* f : vstorage.LevelFiles(0)) {
+    ret.emplace_back(0, f, f->fd.GetFileSize(), f->compensated_file_size,
+                     f->being_compacted);
+  }
+  for (int level = 1; level < vstorage.num_levels(); level++) {
+    uint64_t total_compensated_size = 0U;
+    uint64_t total_size = 0U;
+    bool being_compacted = false;
+    for (FileMetaData* f : vstorage.LevelFiles(level)) {
+      total_compensated_size += f->compensated_file_size;
+      total_size += f->fd.GetFileSize();
+      // Size amp, read amp and periodic compactions always include all files
+      // for a non-zero level. However, a delete triggered compaction and
+      // a trivial move might pick a subset of files in a sorted run. So
+      // always check all files in a sorted run and mark the entire run as
+      // being compacted if one or more files are being compacted
+      if (f->being_compacted) {
+        being_compacted = f->being_compacted;
+      }
+    }
+    if (total_compensated_size > 0) {
+      ret.emplace_back(level, nullptr, total_size, total_compensated_size,
+                       being_compacted);
+    }
+  }
+  return ret;
+}
+
+// Universal style of compaction. Pick files that are contiguous in
+// time-range to compact.
+Compaction* UniversalCompactionBuilder::PickCompaction() {
+  const int kLevel0 = 0;
+  score_ = vstorage_->CompactionScore(kLevel0);
+  sorted_runs_ = CalculateSortedRuns(*vstorage_);
+
+  if (sorted_runs_.size() == 0 ||
+      (vstorage_->FilesMarkedForPeriodicCompaction().empty() &&
+       vstorage_->FilesMarkedForCompaction().empty() &&
+       sorted_runs_.size() < (unsigned int)mutable_cf_options_
+                                 .level0_file_num_compaction_trigger)) {
+    ROCKS_LOG_BUFFER(log_buffer_, "[%s] Universal: nothing to do\n",
+                     cf_name_.c_str());
+    TEST_SYNC_POINT_CALLBACK(
+        "UniversalCompactionBuilder::PickCompaction:Return", nullptr);
+    return nullptr;
+  }
+  VersionStorageInfo::LevelSummaryStorage tmp;
+  ROCKS_LOG_BUFFER_MAX_SZ(
+      log_buffer_, 3072,
+      "[%s] Universal: sorted runs: %" ROCKSDB_PRIszt " files: %s\n",
+      cf_name_.c_str(), sorted_runs_.size(), vstorage_->LevelSummary(&tmp));
+
+  Compaction* c = nullptr;
+  // Periodic compaction has higher priority than other type of compaction
+  // because it's a hard requirement.
+  if (!vstorage_->FilesMarkedForPeriodicCompaction().empty()) {
+    // Always need to do a full compaction for periodic compaction.
+    c = PickPeriodicCompaction();
+  }
+
+  // Check for size amplification.
+  if (c == nullptr &&
+      sorted_runs_.size() >=
+          static_cast<size_t>(
+              mutable_cf_options_.level0_file_num_compaction_trigger)) {
+    if ((c = PickCompactionToReduceSizeAmp()) != nullptr) {
+      ROCKS_LOG_BUFFER(log_buffer_, "[%s] Universal: compacting for size amp\n",
+                       cf_name_.c_str());
+    } else {
+      // Size amplification is within limits. Try reducing read
+      // amplification while maintaining file size ratios.
+      unsigned int ratio =
+          mutable_cf_options_.compaction_options_universal.size_ratio;
+
+      if ((c = PickCompactionToReduceSortedRuns(ratio, UINT_MAX)) != nullptr) {
+        ROCKS_LOG_BUFFER(log_buffer_,
+                         "[%s] Universal: compacting for size ratio\n",
+                         cf_name_.c_str());
+      } else {
+        // Size amplification and file size ratios are within configured limits.
+        // If max read amplification is exceeding configured limits, then force
+        // compaction without looking at filesize ratios and try to reduce
+        // the number of files to fewer than level0_file_num_compaction_trigger.
+        // This is guaranteed by NeedsCompaction()
+        assert(sorted_runs_.size() >=
+               static_cast<size_t>(
+                   mutable_cf_options_.level0_file_num_compaction_trigger));
+        // Get the total number of sorted runs that are not being compacted
+        int num_sr_not_compacted = 0;
+        for (size_t i = 0; i < sorted_runs_.size(); i++) {
+          if (sorted_runs_[i].being_compacted == false) {
+            num_sr_not_compacted++;
+          }
+        }
+
+        // The number of sorted runs that are not being compacted is greater
+        // than the maximum allowed number of sorted runs
+        if (num_sr_not_compacted >
+            mutable_cf_options_.level0_file_num_compaction_trigger) {
+          unsigned int num_files =
+              num_sr_not_compacted -
+              mutable_cf_options_.level0_file_num_compaction_trigger + 1;
+          if ((c = PickCompactionToReduceSortedRuns(UINT_MAX, num_files)) !=
+              nullptr) {
+            ROCKS_LOG_BUFFER(log_buffer_,
+                             "[%s] Universal: compacting for file num -- %u\n",
+                             cf_name_.c_str(), num_files);
+          }
+        }
+      }
+    }
+  }
+
+  if (c == nullptr) {
+    if ((c = PickDeleteTriggeredCompaction()) != nullptr) {
+      ROCKS_LOG_BUFFER(log_buffer_,
+                       "[%s] Universal: delete triggered compaction\n",
+                       cf_name_.c_str());
+    }
+  }
+
+  if (c == nullptr) {
+    TEST_SYNC_POINT_CALLBACK(
+        "UniversalCompactionBuilder::PickCompaction:Return", nullptr);
+    return nullptr;
+  }
+
+  if (mutable_cf_options_.compaction_options_universal.allow_trivial_move ==
+          true &&
+      c->compaction_reason() != CompactionReason::kPeriodicCompaction) {
+    c->set_is_trivial_move(IsInputFilesNonOverlapping(c));
+  }
+
+// validate that all the chosen files of L0 are non overlapping in time
+#ifndef NDEBUG
+  bool is_first = true;
+
+  size_t level_index = 0U;
+  if (c->start_level() == 0) {
+    for (auto f : *c->inputs(0)) {
+      assert(f->fd.smallest_seqno <= f->fd.largest_seqno);
+      if (is_first) {
+        is_first = false;
+      }
+    }
+    level_index = 1U;
+  }
+  for (; level_index < c->num_input_levels(); level_index++) {
+    if (c->num_input_files(level_index) != 0) {
+      SequenceNumber smallest_seqno = 0U;
+      SequenceNumber largest_seqno = 0U;
+      GetSmallestLargestSeqno(*(c->inputs(level_index)), &smallest_seqno,
+                              &largest_seqno);
+      if (is_first) {
+        is_first = false;
+      }
+    }
+  }
+#endif
+  // update statistics
+  size_t num_files = 0;
+  for (auto& each_level : *c->inputs()) {
+    num_files += each_level.files.size();
+  }
+  RecordInHistogram(ioptions_.stats, NUM_FILES_IN_SINGLE_COMPACTION, num_files);
+
+  picker_->RegisterCompaction(c);
+  vstorage_->ComputeCompactionScore(ioptions_, mutable_cf_options_);
+
+  TEST_SYNC_POINT_CALLBACK("UniversalCompactionBuilder::PickCompaction:Return",
+                           c);
+  return c;
+}
+
+uint32_t UniversalCompactionBuilder::GetPathId(
+    const ImmutableCFOptions& ioptions,
+    const MutableCFOptions& mutable_cf_options, uint64_t file_size) {
+  // Two conditions need to be satisfied:
+  // (1) the target path needs to be able to hold the file's size
+  // (2) Total size left in this and previous paths need to be not
+  //     smaller than expected future file size before this new file is
+  //     compacted, which is estimated based on size_ratio.
+  // For example, if now we are compacting files of size (1, 1, 2, 4, 8),
+  // we will make sure the target file, probably with size of 16, will be
+  // placed in a path so that eventually when new files are generated and
+  // compacted to (1, 1, 2, 4, 8, 16), all those files can be stored in or
+  // before the path we chose.
+  //
+  // TODO(sdong): now the case of multiple column families is not
+  // considered in this algorithm. So the target size can be violated in
+  // that case. We need to improve it.
+  uint64_t accumulated_size = 0;
+  uint64_t future_size =
+      file_size *
+      (100 - mutable_cf_options.compaction_options_universal.size_ratio) / 100;
+  uint32_t p = 0;
+  assert(!ioptions.cf_paths.empty());
+  for (; p < ioptions.cf_paths.size() - 1; p++) {
+    uint64_t target_size = ioptions.cf_paths[p].target_size;
+    if (target_size > file_size &&
+        accumulated_size + (target_size - file_size) > future_size) {
+      return p;
+    }
+    accumulated_size += target_size;
+  }
+  return p;
+}
+
+//
+// Consider compaction files based on their size differences with
+// the next file in time order.
+//
+Compaction* UniversalCompactionBuilder::PickCompactionToReduceSortedRuns(
+    unsigned int ratio, unsigned int max_number_of_files_to_compact) {
+  unsigned int min_merge_width =
+      mutable_cf_options_.compaction_options_universal.min_merge_width;
+  unsigned int max_merge_width =
+      mutable_cf_options_.compaction_options_universal.max_merge_width;
+
+  const SortedRun* sr = nullptr;
+  bool done = false;
+  size_t start_index = 0;
+  unsigned int candidate_count = 0;
+
+  unsigned int max_files_to_compact =
+      std::min(max_merge_width, max_number_of_files_to_compact);
+  min_merge_width = std::max(min_merge_width, 2U);
+
+  // Caller checks the size before executing this function. This invariant is
+  // important because otherwise we may have a possible integer underflow when
+  // dealing with unsigned types.
+  assert(sorted_runs_.size() > 0);
+
+  // Considers a candidate file only if it is smaller than the
+  // total size accumulated so far.
+  for (size_t loop = 0; loop < sorted_runs_.size(); loop++) {
+    candidate_count = 0;
+
+    // Skip files that are already being compacted
+    for (sr = nullptr; loop < sorted_runs_.size(); loop++) {
+      sr = &sorted_runs_[loop];
+
+      if (!sr->being_compacted) {
+        candidate_count = 1;
+        break;
+      }
+      char file_num_buf[kFormatFileNumberBufSize];
+      sr->Dump(file_num_buf, sizeof(file_num_buf));
+      ROCKS_LOG_BUFFER(log_buffer_,
+                       "[%s] Universal: %s"
+                       "[%d] being compacted, skipping",
+                       cf_name_.c_str(), file_num_buf, loop);
+
+      sr = nullptr;
+    }
+
+    // This file is not being compacted. Consider it as the
+    // first candidate to be compacted.
+    uint64_t candidate_size = sr != nullptr ? sr->compensated_file_size : 0;
+    if (sr != nullptr) {
+      char file_num_buf[kFormatFileNumberBufSize];
+      sr->Dump(file_num_buf, sizeof(file_num_buf), true);
+      ROCKS_LOG_BUFFER(log_buffer_,
+                       "[%s] Universal: Possible candidate %s[%d].",
+                       cf_name_.c_str(), file_num_buf, loop);
+    }
+
+    // Check if the succeeding files need compaction.
+    for (size_t i = loop + 1;
+         candidate_count < max_files_to_compact && i < sorted_runs_.size();
+         i++) {
+      const SortedRun* succeeding_sr = &sorted_runs_[i];
+      if (succeeding_sr->being_compacted) {
+        break;
+      }
+      // Pick files if the total/last candidate file size (increased by the
+      // specified ratio) is still larger than the next candidate file.
+      // candidate_size is the total size of files picked so far with the
+      // default kCompactionStopStyleTotalSize; with
+      // kCompactionStopStyleSimilarSize, it's simply the size of the last
+      // picked file.
+      double sz = candidate_size * (100.0 + ratio) / 100.0;
+      if (sz < static_cast<double>(succeeding_sr->size)) {
+        break;
+      }
+      if (mutable_cf_options_.compaction_options_universal.stop_style ==
+          kCompactionStopStyleSimilarSize) {
+        // Similar-size stopping rule: also check the last picked file isn't
+        // far larger than the next candidate file.
+        sz = (succeeding_sr->size * (100.0 + ratio)) / 100.0;
+        if (sz < static_cast<double>(candidate_size)) {
+          // If the small file we've encountered begins a run of similar-size
+          // files, we'll pick them up on a future iteration of the outer
+          // loop. If it's some lonely straggler, it'll eventually get picked
+          // by the last-resort read amp strategy which disregards size ratios.
+          break;
+        }
+        candidate_size = succeeding_sr->compensated_file_size;
+      } else {  // default kCompactionStopStyleTotalSize
+        candidate_size += succeeding_sr->compensated_file_size;
+      }
+      candidate_count++;
+    }
+
+    // Found a series of consecutive files that need compaction.
+    if (candidate_count >= (unsigned int)min_merge_width) {
+      start_index = loop;
+      done = true;
+      break;
+    } else {
+      for (size_t i = loop;
+           i < loop + candidate_count && i < sorted_runs_.size(); i++) {
+        const SortedRun* skipping_sr = &sorted_runs_[i];
+        char file_num_buf[256];
+        skipping_sr->DumpSizeInfo(file_num_buf, sizeof(file_num_buf), loop);
+        ROCKS_LOG_BUFFER(log_buffer_, "[%s] Universal: Skipping %s",
+                         cf_name_.c_str(), file_num_buf);
+      }
+    }
+  }
+  if (!done || candidate_count <= 1) {
+    return nullptr;
+  }
+  size_t first_index_after = start_index + candidate_count;
+  // Compression is enabled if files compacted earlier already reached
+  // size ratio of compression.
+  bool enable_compression = true;
+  int ratio_to_compress =
+      mutable_cf_options_.compaction_options_universal.compression_size_percent;
+  if (ratio_to_compress >= 0) {
+    uint64_t total_size = 0;
+    for (auto& sorted_run : sorted_runs_) {
+      total_size += sorted_run.compensated_file_size;
+    }
+
+    uint64_t older_file_size = 0;
+    for (size_t i = sorted_runs_.size() - 1; i >= first_index_after; i--) {
+      older_file_size += sorted_runs_[i].size;
+      if (older_file_size * 100L >= total_size * (long)ratio_to_compress) {
+        enable_compression = false;
+        break;
+      }
+    }
+  }
+
+  uint64_t estimated_total_size = 0;
+  for (unsigned int i = 0; i < first_index_after; i++) {
+    estimated_total_size += sorted_runs_[i].size;
+  }
+  uint32_t path_id =
+      GetPathId(ioptions_, mutable_cf_options_, estimated_total_size);
+  int start_level = sorted_runs_[start_index].level;
+  int output_level;
+  if (first_index_after == sorted_runs_.size()) {
+    output_level = vstorage_->num_levels() - 1;
+  } else if (sorted_runs_[first_index_after].level == 0) {
+    output_level = 0;
+  } else {
+    output_level = sorted_runs_[first_index_after].level - 1;
+  }
+
+  // last level is reserved for the files ingested behind
+  if (ioptions_.allow_ingest_behind &&
+      (output_level == vstorage_->num_levels() - 1)) {
+    assert(output_level > 1);
+    output_level--;
+  }
+
+  std::vector<CompactionInputFiles> inputs(vstorage_->num_levels());
+  for (size_t i = 0; i < inputs.size(); ++i) {
+    inputs[i].level = start_level + static_cast<int>(i);
+  }
+  for (size_t i = start_index; i < first_index_after; i++) {
+    auto& picking_sr = sorted_runs_[i];
+    if (picking_sr.level == 0) {
+      FileMetaData* picking_file = picking_sr.file;
+      inputs[0].files.push_back(picking_file);
+    } else {
+      auto& files = inputs[picking_sr.level - start_level].files;
+      for (auto* f : vstorage_->LevelFiles(picking_sr.level)) {
+        files.push_back(f);
+      }
+    }
+    char file_num_buf[256];
+    picking_sr.DumpSizeInfo(file_num_buf, sizeof(file_num_buf), i);
+    ROCKS_LOG_BUFFER(log_buffer_, "[%s] Universal: Picking %s",
+                     cf_name_.c_str(), file_num_buf);
+  }
+
+  std::vector<FileMetaData*> grandparents;
+  // Include grandparents for potential file cutting in incremental
+  // mode. It is for aligning file cutting boundaries across levels,
+  // so that subsequent compactions can pick files with aligned
+  // buffer.
+  // Single files are only picked up in incremental mode, so that
+  // there is no need for full range.
+  if (mutable_cf_options_.compaction_options_universal.incremental &&
+      first_index_after < sorted_runs_.size() &&
+      sorted_runs_[first_index_after].level > 1) {
+    grandparents = vstorage_->LevelFiles(sorted_runs_[first_index_after].level);
+  }
+
+  if (output_level != 0 &&
+      picker_->FilesRangeOverlapWithCompaction(
+          inputs, output_level,
+          Compaction::EvaluatePenultimateLevel(vstorage_, ioptions_,
+                                               start_level, output_level))) {
+    return nullptr;
+  }
+  CompactionReason compaction_reason;
+  if (max_number_of_files_to_compact == UINT_MAX) {
+    compaction_reason = CompactionReason::kUniversalSizeRatio;
+  } else {
+    compaction_reason = CompactionReason::kUniversalSortedRunNum;
+  }
+  return new Compaction(vstorage_, ioptions_, mutable_cf_options_,
+                        mutable_db_options_, std::move(inputs), output_level,
+                        MaxFileSizeForLevel(mutable_cf_options_, output_level,
+                                            kCompactionStyleUniversal),
+                        GetMaxOverlappingBytes(), path_id,
+                        GetCompressionType(vstorage_, mutable_cf_options_,
+                                           output_level, 1, enable_compression),
+                        GetCompressionOptions(mutable_cf_options_, vstorage_,
+                                              output_level, enable_compression),
+                        Temperature::kUnknown,
+                        /* max_subcompactions */ 0, grandparents,
+                        /* is manual */ false, /* trim_ts */ "", score_,
+                        false /* deletion_compaction */,
+                        /* l0_files_might_overlap */ true, compaction_reason);
+}
+
+// Look at overall size amplification. If size amplification
+// exceeds the configured value, then do a compaction
+// of the candidate files all the way upto the earliest
+// base file (overrides configured values of file-size ratios,
+// min_merge_width and max_merge_width).
+//
+Compaction* UniversalCompactionBuilder::PickCompactionToReduceSizeAmp() {
+  // percentage flexibility while reducing size amplification
+  uint64_t ratio = mutable_cf_options_.compaction_options_universal
+                       .max_size_amplification_percent;
+
+  unsigned int candidate_count = 0;
+  uint64_t candidate_size = 0;
+  size_t start_index = 0;
+  const SortedRun* sr = nullptr;
+
+  assert(!sorted_runs_.empty());
+  if (sorted_runs_.back().being_compacted) {
+    return nullptr;
+  }
+
+  // Skip files that are already being compacted
+  for (size_t loop = 0; loop + 1 < sorted_runs_.size(); loop++) {
+    sr = &sorted_runs_[loop];
+    if (!sr->being_compacted) {
+      start_index = loop;  // Consider this as the first candidate.
+      break;
+    }
+    char file_num_buf[kFormatFileNumberBufSize];
+    sr->Dump(file_num_buf, sizeof(file_num_buf), true);
+    ROCKS_LOG_BUFFER(log_buffer_,
+                     "[%s] Universal: skipping %s[%d] compacted %s",
+                     cf_name_.c_str(), file_num_buf, loop,
+                     " cannot be a candidate to reduce size amp.\n");
+    sr = nullptr;
+  }
+
+  if (sr == nullptr) {
+    return nullptr;  // no candidate files
+  }
+  {
+    char file_num_buf[kFormatFileNumberBufSize];
+    sr->Dump(file_num_buf, sizeof(file_num_buf), true);
+    ROCKS_LOG_BUFFER(
+        log_buffer_,
+        "[%s] Universal: First candidate %s[%" ROCKSDB_PRIszt "] %s",
+        cf_name_.c_str(), file_num_buf, start_index, " to reduce size amp.\n");
+  }
+
+  // size of the base sorted run for size amp calculation
+  uint64_t base_sr_size = sorted_runs_.back().size;
+  size_t sr_end_idx = sorted_runs_.size() - 1;
+  // If tiered compaction is enabled and the last sorted run is the last level
+  if (ioptions_.preclude_last_level_data_seconds > 0 &&
+      ioptions_.num_levels > 2 &&
+      sorted_runs_.back().level == ioptions_.num_levels - 1 &&
+      sorted_runs_.size() > 1) {
+    sr_end_idx = sorted_runs_.size() - 2;
+    base_sr_size = sorted_runs_[sr_end_idx].size;
+  }
+
+  // keep adding up all the remaining files
+  for (size_t loop = start_index; loop < sr_end_idx; loop++) {
+    sr = &sorted_runs_[loop];
+    if (sr->being_compacted) {
+      // TODO with incremental compaction is supported, we might want to
+      // schedule some incremental compactions in parallel if needed.
+      char file_num_buf[kFormatFileNumberBufSize];
+      sr->Dump(file_num_buf, sizeof(file_num_buf), true);
+      ROCKS_LOG_BUFFER(
+          log_buffer_, "[%s] Universal: Possible candidate %s[%d] %s",
+          cf_name_.c_str(), file_num_buf, start_index,
+          " is already being compacted. No size amp reduction possible.\n");
+      return nullptr;
+    }
+    candidate_size += sr->compensated_file_size;
+    candidate_count++;
+  }
+  if (candidate_count == 0) {
+    return nullptr;
+  }
+
+  // size amplification = percentage of additional size
+  if (candidate_size * 100 < ratio * base_sr_size) {
+    ROCKS_LOG_BUFFER(
+        log_buffer_,
+        "[%s] Universal: size amp not needed. newer-files-total-size %" PRIu64
+        " earliest-file-size %" PRIu64,
+        cf_name_.c_str(), candidate_size, base_sr_size);
+    return nullptr;
+  } else {
+    ROCKS_LOG_BUFFER(
+        log_buffer_,
+        "[%s] Universal: size amp needed. newer-files-total-size %" PRIu64
+        " earliest-file-size %" PRIu64,
+        cf_name_.c_str(), candidate_size, base_sr_size);
+  }
+  // Since incremental compaction can't include more than second last
+  // level, it can introduce penalty, compared to full compaction. We
+  // hard code the pentalty to be 80%. If we end up with a compaction
+  // fanout higher than 80% of full level compactions, we fall back
+  // to full level compaction.
+  // The 80% threshold is arbitrary and can be adjusted or made
+  // configurable in the future.
+  // This also prevent the case when compaction falls behind and we
+  // need to compact more levels for compactions to catch up.
+  if (mutable_cf_options_.compaction_options_universal.incremental) {
+    double fanout_threshold = static_cast<double>(base_sr_size) /
+                              static_cast<double>(candidate_size) * 1.8;
+    Compaction* picked = PickIncrementalForReduceSizeAmp(fanout_threshold);
+    if (picked != nullptr) {
+      // As the feature is still incremental, picking incremental compaction
+      // might fail and we will fall bck to compacting full level.
+      return picked;
+    }
+  }
+  return PickCompactionWithSortedRunRange(
+      start_index, sr_end_idx, CompactionReason::kUniversalSizeAmplification);
+}
+
+Compaction* UniversalCompactionBuilder::PickIncrementalForReduceSizeAmp(
+    double fanout_threshold) {
+  // Try find all potential compactions with total size just over
+  // options.max_compaction_size / 2, and take the one with the lowest
+  // fanout (defined in declaration of the function).
+  // This is done by having a sliding window of the files at the second
+  // lowest level, and keep expanding while finding overlapping in the
+  // last level. Once total size exceeds the size threshold, calculate
+  // the fanout value. And then shrinking from the small side of the
+  // window. Keep doing it until the end.
+  // Finally, we try to include upper level files if they fall into
+  // the range.
+  //
+  // Note that it is a similar problem as leveled compaction's
+  // kMinOverlappingRatio priority, but instead of picking single files
+  // we expand to a target compaction size. The reason is that in
+  // leveled compaction, actual fanout value tends to high, e.g. 10, so
+  // even with single file in down merging level, the extra size
+  // compacted in boundary files is at a lower ratio. But here users
+  // often have size of second last level size to be 1/4, 1/3 or even
+  // 1/2 of the bottommost level, so picking single file in second most
+  // level will cause significant waste, which is not desirable.
+  //
+  // This algorithm has lots of room to improve to pick more efficient
+  // compactions.
+  assert(sorted_runs_.size() >= 2);
+  int second_last_level = sorted_runs_[sorted_runs_.size() - 2].level;
+  if (second_last_level == 0) {
+    // Can't split Level 0.
+    return nullptr;
+  }
+  int output_level = sorted_runs_.back().level;
+  const std::vector<FileMetaData*>& bottom_files =
+      vstorage_->LevelFiles(output_level);
+  const std::vector<FileMetaData*>& files =
+      vstorage_->LevelFiles(second_last_level);
+  assert(!bottom_files.empty());
+  assert(!files.empty());
+
+  //  std::unordered_map<uint64_t, uint64_t> file_to_order;
+
+  int picked_start_idx = 0;
+  int picked_end_idx = 0;
+  double picked_fanout = fanout_threshold;
+
+  // Use half target compaction bytes as anchor to stop growing second most
+  // level files, and reserve growing space for more overlapping bottom level,
+  // clean cut, files from other levels, etc.
+  uint64_t comp_thres_size = mutable_cf_options_.max_compaction_bytes / 2;
+  int start_idx = 0;
+  int bottom_end_idx = 0;
+  int bottom_start_idx = 0;
+  uint64_t non_bottom_size = 0;
+  uint64_t bottom_size = 0;
+  bool end_bottom_size_counted = false;
+  for (int end_idx = 0; end_idx < static_cast<int>(files.size()); end_idx++) {
+    FileMetaData* end_file = files[end_idx];
+
+    // Include bottom most level files smaller than the current second
+    // last level file.
+    int num_skipped = 0;
+    while (bottom_end_idx < static_cast<int>(bottom_files.size()) &&
+           icmp_->Compare(bottom_files[bottom_end_idx]->largest,
+                          end_file->smallest) < 0) {
+      if (!end_bottom_size_counted) {
+        bottom_size += bottom_files[bottom_end_idx]->fd.file_size;
+      }
+      bottom_end_idx++;
+      end_bottom_size_counted = false;
+      num_skipped++;
+    }
+
+    if (num_skipped > 1) {
+      // At least a file in the bottom most level falls into the file gap. No
+      // reason to include the file. We cut the range and start a new sliding
+      // window.
+      start_idx = end_idx;
+    }
+
+    if (start_idx == end_idx) {
+      // new sliding window.
+      non_bottom_size = 0;
+      bottom_size = 0;
+      bottom_start_idx = bottom_end_idx;
+      end_bottom_size_counted = false;
+    }
+
+    non_bottom_size += end_file->fd.file_size;
+
+    // Include all overlapping files in bottom level.
+    while (bottom_end_idx < static_cast<int>(bottom_files.size()) &&
+           icmp_->Compare(bottom_files[bottom_end_idx]->smallest,
+                          end_file->largest) < 0) {
+      if (!end_bottom_size_counted) {
+        bottom_size += bottom_files[bottom_end_idx]->fd.file_size;
+        end_bottom_size_counted = true;
+      }
+      if (icmp_->Compare(bottom_files[bottom_end_idx]->largest,
+                         end_file->largest) > 0) {
+        // next level file cross large boundary of current file.
+        break;
+      }
+      bottom_end_idx++;
+      end_bottom_size_counted = false;
+    }
+
+    if ((non_bottom_size + bottom_size > comp_thres_size ||
+         end_idx == static_cast<int>(files.size()) - 1) &&
+        non_bottom_size > 0) {  // Do we alow 0 size file at all?
+      // If it is a better compaction, remember it in picked* variables.
+      double fanout = static_cast<double>(bottom_size) /
+                      static_cast<double>(non_bottom_size);
+      if (fanout < picked_fanout) {
+        picked_start_idx = start_idx;
+        picked_end_idx = end_idx;
+        picked_fanout = fanout;
+      }
+      // Shrink from the start end to under comp_thres_size
+      while (non_bottom_size + bottom_size > comp_thres_size &&
+             start_idx <= end_idx) {
+        non_bottom_size -= files[start_idx]->fd.file_size;
+        start_idx++;
+        if (start_idx < static_cast<int>(files.size())) {
+          while (bottom_start_idx <= bottom_end_idx &&
+                 icmp_->Compare(bottom_files[bottom_start_idx]->largest,
+                                files[start_idx]->smallest) < 0) {
+            bottom_size -= bottom_files[bottom_start_idx]->fd.file_size;
+            bottom_start_idx++;
+          }
+        }
+      }
+    }
+  }
+
+  if (picked_fanout >= fanout_threshold) {
+    assert(picked_fanout == fanout_threshold);
+    return nullptr;
+  }
+
+  std::vector<CompactionInputFiles> inputs;
+  CompactionInputFiles bottom_level_inputs;
+  CompactionInputFiles second_last_level_inputs;
+  second_last_level_inputs.level = second_last_level;
+  bottom_level_inputs.level = output_level;
+  for (int i = picked_start_idx; i <= picked_end_idx; i++) {
+    if (files[i]->being_compacted) {
+      return nullptr;
+    }
+    second_last_level_inputs.files.push_back(files[i]);
+  }
+  assert(!second_last_level_inputs.empty());
+  if (!picker_->ExpandInputsToCleanCut(cf_name_, vstorage_,
+                                       &second_last_level_inputs,
+                                       /*next_smallest=*/nullptr)) {
+    return nullptr;
+  }
+  // We might be able to avoid this binary search if we save and expand
+  // from bottom_start_idx and bottom_end_idx, but for now, we use
+  // SetupOtherInputs() for simplicity.
+  int parent_index = -1;  // Create and use bottom_start_idx?
+  if (!picker_->SetupOtherInputs(cf_name_, mutable_cf_options_, vstorage_,
+                                 &second_last_level_inputs,
+                                 &bottom_level_inputs, &parent_index,
+                                 /*base_index=*/-1)) {
+    return nullptr;
+  }
+
+  // Try to include files in upper levels if they fall into the range.
+  // Since we need to go from lower level up and this is in the reverse
+  // order, compared to level order, we first write to an reversed
+  // data structure and finally copy them to compaction inputs.
+  InternalKey smallest, largest;
+  picker_->GetRange(second_last_level_inputs, &smallest, &largest);
+  std::vector<CompactionInputFiles> inputs_reverse;
+  for (auto it = ++(++sorted_runs_.rbegin()); it != sorted_runs_.rend(); it++) {
+    SortedRun& sr = *it;
+    if (sr.level == 0) {
+      break;
+    }
+    std::vector<FileMetaData*> level_inputs;
+    vstorage_->GetCleanInputsWithinInterval(sr.level, &smallest, &largest,
+                                            &level_inputs);
+    if (!level_inputs.empty()) {
+      inputs_reverse.push_back({});
+      inputs_reverse.back().level = sr.level;
+      inputs_reverse.back().files = level_inputs;
+      picker_->GetRange(inputs_reverse.back(), &smallest, &largest);
+    }
+  }
+  for (auto it = inputs_reverse.rbegin(); it != inputs_reverse.rend(); it++) {
+    inputs.push_back(*it);
+  }
+
+  inputs.push_back(second_last_level_inputs);
+  inputs.push_back(bottom_level_inputs);
+
+  int start_level = Compaction::kInvalidLevel;
+  for (const auto& in : inputs) {
+    if (!in.empty()) {
+      // inputs should already be sorted by level
+      start_level = in.level;
+      break;
+    }
+  }
+
+  // intra L0 compactions outputs could have overlap
+  if (output_level != 0 &&
+      picker_->FilesRangeOverlapWithCompaction(
+          inputs, output_level,
+          Compaction::EvaluatePenultimateLevel(vstorage_, ioptions_,
+                                               start_level, output_level))) {
+    return nullptr;
+  }
+
+  // TODO support multi paths?
+  uint32_t path_id = 0;
+  return new Compaction(
+      vstorage_, ioptions_, mutable_cf_options_, mutable_db_options_,
+      std::move(inputs), output_level,
+      MaxFileSizeForLevel(mutable_cf_options_, output_level,
+                          kCompactionStyleUniversal),
+      GetMaxOverlappingBytes(), path_id,
+      GetCompressionType(vstorage_, mutable_cf_options_, output_level, 1,
+                         true /* enable_compression */),
+      GetCompressionOptions(mutable_cf_options_, vstorage_, output_level,
+                            true /* enable_compression */),
+      Temperature::kUnknown,
+      /* max_subcompactions */ 0, /* grandparents */ {}, /* is manual */ false,
+      /* trim_ts */ "", score_, false /* deletion_compaction */,
+      /* l0_files_might_overlap */ true,
+      CompactionReason::kUniversalSizeAmplification);
+}
+
+// Pick files marked for compaction. Typically, files are marked by
+// CompactOnDeleteCollector due to the presence of tombstones.
+Compaction* UniversalCompactionBuilder::PickDeleteTriggeredCompaction() {
+  CompactionInputFiles start_level_inputs;
+  int output_level;
+  std::vector<CompactionInputFiles> inputs;
+  std::vector<FileMetaData*> grandparents;
+
+  if (vstorage_->num_levels() == 1) {
+    // This is single level universal. Since we're basically trying to reclaim
+    // space by processing files marked for compaction due to high tombstone
+    // density, let's do the same thing as compaction to reduce size amp which
+    // has the same goals.
+    int start_index = -1;
+
+    start_level_inputs.level = 0;
+    start_level_inputs.files.clear();
+    output_level = 0;
+    // Find the first file marked for compaction. Ignore the last file
+    for (size_t loop = 0; loop + 1 < sorted_runs_.size(); loop++) {
+      SortedRun* sr = &sorted_runs_[loop];
+      if (sr->being_compacted) {
+        continue;
+      }
+      FileMetaData* f = vstorage_->LevelFiles(0)[loop];
+      if (f->marked_for_compaction) {
+        start_level_inputs.files.push_back(f);
+        start_index =
+            static_cast<int>(loop);  // Consider this as the first candidate.
+        break;
+      }
+    }
+    if (start_index < 0) {
+      // Either no file marked, or they're already being compacted
+      return nullptr;
+    }
+
+    for (size_t loop = start_index + 1; loop < sorted_runs_.size(); loop++) {
+      SortedRun* sr = &sorted_runs_[loop];
+      if (sr->being_compacted) {
+        break;
+      }
+
+      FileMetaData* f = vstorage_->LevelFiles(0)[loop];
+      start_level_inputs.files.push_back(f);
+    }
+    if (start_level_inputs.size() <= 1) {
+      // If only the last file in L0 is marked for compaction, ignore it
+      return nullptr;
+    }
+    inputs.push_back(start_level_inputs);
+  } else {
+    int start_level;
+
+    // For multi-level universal, the strategy is to make this look more like
+    // leveled. We pick one of the files marked for compaction and compact with
+    // overlapping files in the adjacent level.
+    picker_->PickFilesMarkedForCompaction(cf_name_, vstorage_, &start_level,
+                                          &output_level, &start_level_inputs);
+    if (start_level_inputs.empty()) {
+      return nullptr;
+    }
+
+    // Pick the first non-empty level after the start_level
+    for (output_level = start_level + 1; output_level < vstorage_->num_levels();
+         output_level++) {
+      if (vstorage_->NumLevelFiles(output_level) != 0) {
+        break;
+      }
+    }
+
+    // If all higher levels are empty, pick the highest level as output level
+    if (output_level == vstorage_->num_levels()) {
+      if (start_level == 0) {
+        output_level = vstorage_->num_levels() - 1;
+      } else {
+        // If start level is non-zero and all higher levels are empty, this
+        // compaction will translate into a trivial move. Since the idea is
+        // to reclaim space and trivial move doesn't help with that, we
+        // skip compaction in this case and return nullptr
+        return nullptr;
+      }
+    }
+    if (ioptions_.allow_ingest_behind &&
+        output_level == vstorage_->num_levels() - 1) {
+      assert(output_level > 1);
+      output_level--;
+    }
+
+    if (output_level != 0) {
+      if (start_level == 0) {
+        if (!picker_->GetOverlappingL0Files(vstorage_, &start_level_inputs,
+                                            output_level, nullptr)) {
+          return nullptr;
+        }
+      }
+
+      CompactionInputFiles output_level_inputs;
+      int parent_index = -1;
+
+      output_level_inputs.level = output_level;
+      if (!picker_->SetupOtherInputs(cf_name_, mutable_cf_options_, vstorage_,
+                                     &start_level_inputs, &output_level_inputs,
+                                     &parent_index, -1)) {
+        return nullptr;
+      }
+      inputs.push_back(start_level_inputs);
+      if (!output_level_inputs.empty()) {
+        inputs.push_back(output_level_inputs);
+      }
+      if (picker_->FilesRangeOverlapWithCompaction(
+              inputs, output_level,
+              Compaction::EvaluatePenultimateLevel(
+                  vstorage_, ioptions_, start_level, output_level))) {
+        return nullptr;
+      }
+
+      picker_->GetGrandparents(vstorage_, start_level_inputs,
+                               output_level_inputs, &grandparents);
+    } else {
+      inputs.push_back(start_level_inputs);
+    }
+  }
+
+  uint64_t estimated_total_size = 0;
+  // Use size of the output level as estimated file size
+  for (FileMetaData* f : vstorage_->LevelFiles(output_level)) {
+    estimated_total_size += f->fd.GetFileSize();
+  }
+  uint32_t path_id =
+      GetPathId(ioptions_, mutable_cf_options_, estimated_total_size);
+  return new Compaction(
+      vstorage_, ioptions_, mutable_cf_options_, mutable_db_options_,
+      std::move(inputs), output_level,
+      MaxFileSizeForLevel(mutable_cf_options_, output_level,
+                          kCompactionStyleUniversal),
+      /* max_grandparent_overlap_bytes */ GetMaxOverlappingBytes(), path_id,
+      GetCompressionType(vstorage_, mutable_cf_options_, output_level, 1),
+      GetCompressionOptions(mutable_cf_options_, vstorage_, output_level),
+      Temperature::kUnknown,
+      /* max_subcompactions */ 0, grandparents, /* is manual */ false,
+      /* trim_ts */ "", score_, false /* deletion_compaction */,
+      /* l0_files_might_overlap */ true,
+      CompactionReason::kFilesMarkedForCompaction);
+}
+
+Compaction* UniversalCompactionBuilder::PickCompactionToOldest(
+    size_t start_index, CompactionReason compaction_reason) {
+  return PickCompactionWithSortedRunRange(start_index, sorted_runs_.size() - 1,
+                                          compaction_reason);
+}
+
+Compaction* UniversalCompactionBuilder::PickCompactionWithSortedRunRange(
+    size_t start_index, size_t end_index, CompactionReason compaction_reason) {
+  assert(start_index < sorted_runs_.size());
+
+  // Estimate total file size
+  uint64_t estimated_total_size = 0;
+  for (size_t loop = start_index; loop <= end_index; loop++) {
+    estimated_total_size += sorted_runs_[loop].size;
+  }
+  uint32_t path_id =
+      GetPathId(ioptions_, mutable_cf_options_, estimated_total_size);
+  int start_level = sorted_runs_[start_index].level;
+
+  std::vector<CompactionInputFiles> inputs(vstorage_->num_levels());
+  for (size_t i = 0; i < inputs.size(); ++i) {
+    inputs[i].level = start_level + static_cast<int>(i);
+  }
+  for (size_t loop = start_index; loop <= end_index; loop++) {
+    auto& picking_sr = sorted_runs_[loop];
+    if (picking_sr.level == 0) {
+      FileMetaData* f = picking_sr.file;
+      inputs[0].files.push_back(f);
+    } else {
+      auto& files = inputs[picking_sr.level - start_level].files;
+      for (auto* f : vstorage_->LevelFiles(picking_sr.level)) {
+        files.push_back(f);
+      }
+    }
+    std::string comp_reason_print_string;
+    if (compaction_reason == CompactionReason::kPeriodicCompaction) {
+      comp_reason_print_string = "periodic compaction";
+    } else if (compaction_reason ==
+               CompactionReason::kUniversalSizeAmplification) {
+      comp_reason_print_string = "size amp";
+    } else {
+      assert(false);
+      comp_reason_print_string = "unknown: ";
+      comp_reason_print_string.append(
+          std::to_string(static_cast<int>(compaction_reason)));
+    }
+
+    char file_num_buf[256];
+    picking_sr.DumpSizeInfo(file_num_buf, sizeof(file_num_buf), loop);
+    ROCKS_LOG_BUFFER(log_buffer_, "[%s] Universal: %s picking %s",
+                     cf_name_.c_str(), comp_reason_print_string.c_str(),
+                     file_num_buf);
+  }
+
+  int output_level;
+  if (end_index == sorted_runs_.size() - 1) {
+    // output files at the last level, unless it's reserved
+    output_level = vstorage_->num_levels() - 1;
+    // last level is reserved for the files ingested behind
+    if (ioptions_.allow_ingest_behind) {
+      assert(output_level > 1);
+      output_level--;
+    }
+  } else {
+    // if it's not including all sorted_runs, it can only output to the level
+    // above the `end_index + 1` sorted_run.
+    output_level = sorted_runs_[end_index + 1].level - 1;
+  }
+
+  // intra L0 compactions outputs could have overlap
+  if (output_level != 0 &&
+      picker_->FilesRangeOverlapWithCompaction(
+          inputs, output_level,
+          Compaction::EvaluatePenultimateLevel(vstorage_, ioptions_,
+                                               start_level, output_level))) {
+    return nullptr;
+  }
+
+  // We never check size for
+  // compaction_options_universal.compression_size_percent,
+  // because we always compact all the files, so always compress.
+  return new Compaction(
+      vstorage_, ioptions_, mutable_cf_options_, mutable_db_options_,
+      std::move(inputs), output_level,
+      MaxFileSizeForLevel(mutable_cf_options_, output_level,
+                          kCompactionStyleUniversal),
+      GetMaxOverlappingBytes(), path_id,
+      GetCompressionType(vstorage_, mutable_cf_options_, output_level, 1,
+                         true /* enable_compression */),
+      GetCompressionOptions(mutable_cf_options_, vstorage_, output_level,
+                            true /* enable_compression */),
+      Temperature::kUnknown,
+      /* max_subcompactions */ 0, /* grandparents */ {}, /* is manual */ false,
+      /* trim_ts */ "", score_, false /* deletion_compaction */,
+      /* l0_files_might_overlap */ true, compaction_reason);
+}
+
+Compaction* UniversalCompactionBuilder::PickPeriodicCompaction() {
+  ROCKS_LOG_BUFFER(log_buffer_, "[%s] Universal: Periodic Compaction",
+                   cf_name_.c_str());
+
+  // In universal compaction, sorted runs contain older data are almost always
+  // generated earlier too. To simplify the problem, we just try to trigger
+  // a full compaction. We start from the oldest sorted run and include
+  // all sorted runs, until we hit a sorted already being compacted.
+  // Since usually the largest (which is usually the oldest) sorted run is
+  // included anyway, doing a full compaction won't increase write
+  // amplification much.
+
+  // Get some information from marked files to check whether a file is
+  // included in the compaction.
+
+  size_t start_index = sorted_runs_.size();
+  while (start_index > 0 && !sorted_runs_[start_index - 1].being_compacted) {
+    start_index--;
+  }
+  if (start_index == sorted_runs_.size()) {
+    return nullptr;
+  }
+
+  // There is a rare corner case where we can't pick up all the files
+  // because some files are being compacted and we end up with picking files
+  // but none of them need periodic compaction. Unless we simply recompact
+  // the last sorted run (either the last level or last L0 file), we would just
+  // execute the compaction, in order to simplify  the logic.
+  if (start_index == sorted_runs_.size() - 1) {
+    bool included_file_marked = false;
+    int start_level = sorted_runs_[start_index].level;
+    FileMetaData* start_file = sorted_runs_[start_index].file;
+    for (const std::pair<int, FileMetaData*>& level_file_pair :
+         vstorage_->FilesMarkedForPeriodicCompaction()) {
+      if (start_level != 0) {
+        // Last sorted run is a level
+        if (start_level == level_file_pair.first) {
+          included_file_marked = true;
+          break;
+        }
+      } else {
+        // Last sorted run is a L0 file.
+        if (start_file == level_file_pair.second) {
+          included_file_marked = true;
+          break;
+        }
+      }
+    }
+    if (!included_file_marked) {
+      ROCKS_LOG_BUFFER(log_buffer_,
+                       "[%s] Universal: Cannot form a compaction covering file "
+                       "marked for periodic compaction",
+                       cf_name_.c_str());
+      return nullptr;
+    }
+  }
+
+  Compaction* c = PickCompactionToOldest(start_index,
+                                         CompactionReason::kPeriodicCompaction);
+
+  TEST_SYNC_POINT_CALLBACK(
+      "UniversalCompactionPicker::PickPeriodicCompaction:Return", c);
+
+  return c;
+}
+
+uint64_t UniversalCompactionBuilder::GetMaxOverlappingBytes() const {
+  if (!mutable_cf_options_.compaction_options_universal.incremental) {
+    return std::numeric_limits<uint64_t>::max();
+  } else {
+    // Try to align cutting boundary with files at the next level if the
+    // file isn't end up with 1/2 of target size, or it would overlap
+    // with two full size files at the next level.
+    return mutable_cf_options_.target_file_size_base / 2 * 3;
+  }
+}
+}  // namespace ROCKSDB_NAMESPACE
+
+#endif  // !ROCKSDB_LITE