Move NeedsCompaction() from VersionSet to Version

Summary: There is no reason to have functions NeedCompaction(), MaxCompactionScore() and MaxCompactionScoreLevel() in VersionSet, since they don't access any data in VersionSet.

Test Plan: make check

Reviewers: kailiu, haobo, sdong

Reviewed By: kailiu

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15333

db/db_impl.cc

@@ -1776,7 +1776,7 @@ void DBImpl::MaybeScheduleFlushOrCompaction() {
     // max_background_compactions hasn't been reached and, in case
     // bg_manual_only_ > 0, if it's a manual compaction.
     if ((manual_compaction_ ||
-         versions_->NeedsCompaction() ||
+         versions_->current()->NeedsCompaction() ||
          (is_flush_pending && (options_.max_background_flushes <= 0))) &&
         bg_compaction_scheduled_ < options_.max_background_compactions &&
         (!bg_manual_only_ || manual_compaction_)) {
@@ -3350,12 +3350,11 @@ Status DBImpl::MakeRoomForWrite(bool force,
       RecordTick(options_.statistics.get(), STALL_L0_NUM_FILES_MICROS, stall);
       stall_level0_num_files_ += stall;
       stall_level0_num_files_count_++;
-    } else if (
-        allow_hard_rate_limit_delay &&
-        options_.hard_rate_limit > 1.0 &&
-        (score = versions_->MaxCompactionScore()) > options_.hard_rate_limit) {
+    } else if (allow_hard_rate_limit_delay && options_.hard_rate_limit > 1.0 &&
+               (score = versions_->current()->MaxCompactionScore()) >
+                   options_.hard_rate_limit) {
       // Delay a write when the compaction score for any level is too large.
-      int max_level = versions_->MaxCompactionScoreLevel();
+      int max_level = versions_->current()->MaxCompactionScoreLevel();
       mutex_.Unlock();
       uint64_t delayed;
       {
@@ -3377,10 +3376,9 @@ Status DBImpl::MakeRoomForWrite(bool force,
         allow_hard_rate_limit_delay = false;
       }
       mutex_.Lock();
-    } else if (
-        allow_soft_rate_limit_delay &&
-        options_.soft_rate_limit > 0.0 &&
-        (score = versions_->MaxCompactionScore()) > options_.soft_rate_limit) {
+    } else if (allow_soft_rate_limit_delay && options_.soft_rate_limit > 0.0 &&
+               (score = versions_->current()->MaxCompactionScore()) >
+                   options_.soft_rate_limit) {
       // Delay a write when the compaction score for any level is too large.
       // TODO: add statistics
       mutex_.Unlock();

db/version_set.cc

@@ -756,6 +756,28 @@ void Version::Unref() {
   }
 }
 
+bool Version::NeedsCompaction() const {
+  if (file_to_compact_ != nullptr) {
+    return true;
+  }
+  // In universal compaction case, this check doesn't really
+  // check the compaction condition, but checks num of files threshold
+  // only. We are not going to miss any compaction opportunity
+  // but it's likely that more compactions are scheduled but
+  // ending up with nothing to do. We can improve it later.
+  // TODO(sdong): improve this function to be accurate for universal
+  //              compactions.
+  int num_levels_to_check =
+    (vset_->options_->compaction_style != kCompactionStyleUniversal) ?
+    NumberLevels() - 1 : 1;
+  for (int i = 0; i < num_levels_to_check; i++) {
+    if (compaction_score_[i] >= 1) {
+      return true;
+    }
+  }
+  return false;
+}
+
 bool Version::OverlapInLevel(int level,
                              const Slice* smallest_user_key,
                              const Slice* largest_user_key) {

db/version_set.h

@@ -99,6 +99,15 @@ class Version {
   void Ref();
   void Unref();
 
+  // Returns true iff some level needs a compaction.
+  bool NeedsCompaction() const;
+
+  // Returns the maxmimum compaction score for levels 1 to max
+  double MaxCompactionScore() const { return max_compaction_score_; }
+
+  // See field declaration
+  int MaxCompactionScoreLevel() const { return max_compaction_score_level_; }
+
   void GetOverlappingInputs(
       int level,
       const InternalKey* begin,         // nullptr means before all keys
@@ -368,42 +377,6 @@ class VersionSet {
   // The caller should delete the iterator when no longer needed.
   Iterator* MakeInputIterator(Compaction* c);
 
-  // Returns true iff some level needs a compaction because it has
-  // exceeded its target size.
-  bool NeedsSizeCompaction() const {
-    // In universal compaction case, this check doesn't really
-    // check the compaction condition, but checks num of files threshold
-    // only. We are not going to miss any compaction opportunity
-    // but it's likely that more compactions are scheduled but
-    // ending up with nothing to do. We can improve it later.
-    // TODO: improve this function to be accurate for universal
-    //       compactions.
-    int num_levels_to_check =
-        (options_->compaction_style != kCompactionStyleUniversal) ?
-            NumberLevels() - 1 : 1;
-    for (int i = 0; i < num_levels_to_check; i++) {
-      if (current_->compaction_score_[i] >= 1) {
-        return true;
-      }
-    }
-    return false;
-  }
-  // Returns true iff some level needs a compaction.
-  bool NeedsCompaction() const {
-    return ((current_->file_to_compact_ != nullptr) ||
-            NeedsSizeCompaction());
-  }
-
-  // Returns the maxmimum compaction score for levels 1 to max
-  double MaxCompactionScore() const {
-    return current_->max_compaction_score_;
-  }
-
-  // See field declaration
-  int MaxCompactionScoreLevel() const {
-    return current_->max_compaction_score_level_;
-  }
-
   // Add all files listed in any live version to *live.
   void AddLiveFiles(std::vector<uint64_t>* live_list);