Remove compaction pointers

Summary: The only thing we do with compaction pointers is set them to some values, we never actually read them. I don't know what we used them for, but it doesn't look like we use them anymore.

Test Plan: make check

Reviewers: dhruba, haobo, kailiu, sdong

Reviewed By: kailiu

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15225

db/version_edit.cc

@@ -69,12 +69,6 @@ void VersionEdit::EncodeTo(std::string* dst) const {
     PutVarint64(dst, last_sequence_);
   }
 
-  for (size_t i = 0; i < compact_pointers_.size(); i++) {
-    PutVarint32(dst, kCompactPointer);
-    PutVarint32(dst, compact_pointers_[i].first);  // level
-    PutLengthPrefixedSlice(dst, compact_pointers_[i].second.Encode());
-  }
-
   for (DeletedFileSet::const_iterator iter = deleted_files_.begin();
        iter != deleted_files_.end();
        ++iter) {
@@ -178,7 +172,9 @@ Status VersionEdit::DecodeFrom(const Slice& src) {
       case kCompactPointer:
         if (GetLevel(&input, &level, &msg) &&
             GetInternalKey(&input, &key)) {
-          compact_pointers_.push_back(std::make_pair(level, key));
+          // we don't use compact pointers anymore,
+          // but we should not fail if they are still
+          // in manifest
         } else {
           if (!msg) {
             msg = "compaction pointer";
@@ -267,12 +263,6 @@ std::string VersionEdit::DebugString(bool hex_key) const {
     r.append("\n  LastSeq: ");
     AppendNumberTo(&r, last_sequence_);
   }
-  for (size_t i = 0; i < compact_pointers_.size(); i++) {
-    r.append("\n  CompactPointer: ");
-    AppendNumberTo(&r, compact_pointers_[i].first);
-    r.append(" ");
-    r.append(compact_pointers_[i].second.DebugString(hex_key));
-  }
   for (DeletedFileSet::const_iterator iter = deleted_files_.begin();
        iter != deleted_files_.end();
        ++iter) {

db/version_edit.h

@@ -59,9 +59,6 @@ class VersionEdit {
     has_last_sequence_ = true;
     last_sequence_ = seq;
   }
-  void SetCompactPointer(int level, const InternalKey& key) {
-    compact_pointers_.push_back(std::make_pair(level, key));
-  }
 
   // Add the specified file at the specified number.
   // REQUIRES: This version has not been saved (see VersionSet::SaveTo)
@@ -117,7 +114,6 @@ class VersionEdit {
   bool has_next_file_number_;
   bool has_last_sequence_;
 
-  std::vector<std::pair<int, InternalKey> > compact_pointers_;
   DeletedFileSet deleted_files_;
   std::vector<std::pair<int, FileMetaData> > new_files_;
 };

db/version_edit_test.cc

@@ -36,7 +36,6 @@ TEST(VersionEditTest, EncodeDecode) {
                  kBig + 500 + i,
                  kBig + 600 + i);
     edit.DeleteFile(4, kBig + 700 + i);
-    edit.SetCompactPointer(i, InternalKey("x", kBig + 900 + i, kTypeValue));
   }
 
   edit.SetComparatorName("foo");

db/version_set.cc

@@ -1245,13 +1245,6 @@ class VersionSet::Builder {
   void Apply(VersionEdit* edit) {
     CheckConsistency(base_);
 
-    // Update compaction pointers
-    for (size_t i = 0; i < edit->compact_pointers_.size(); i++) {
-      const int level = edit->compact_pointers_[i].first;
-      vset_->compact_pointer_[level] =
-          edit->compact_pointers_[i].second.Encode().ToString();
-    }
-
     // Delete files
     const VersionEdit::DeletedFileSet& del = edit->deleted_files_;
     for (VersionEdit::DeletedFileSet::const_iterator iter = del.begin();
@@ -1365,7 +1358,6 @@ VersionSet::VersionSet(const std::string& dbname, const Options* options,
       manifest_file_size_(0),
       storage_options_(storage_options),
       storage_options_compactions_(storage_options_) {
-  compact_pointer_ = new std::string[options_->num_levels];
   if (options_->compaction_style == kCompactionStyleUniversal) {
     compaction_picker_.reset(new UniversalCompactionPicker(options_, &icmp_));
   } else {
@@ -1381,7 +1373,6 @@ VersionSet::~VersionSet() {
     delete file;
   }
   obsolete_files_.clear();
-  delete[] compact_pointer_;
 }
 
 void VersionSet::AppendVersion(Version* v) {
@@ -1881,15 +1872,6 @@ Status VersionSet::WriteSnapshot(log::Writer* log) {
   VersionEdit edit;
   edit.SetComparatorName(icmp_.user_comparator()->Name());
 
-  // Save compaction pointers
-  for (int level = 0; level < NumberLevels(); level++) {
-    if (!compact_pointer_[level].empty()) {
-      InternalKey key;
-      key.DecodeFrom(compact_pointer_[level]);
-      edit.SetCompactPointer(level, key);
-    }
-  }
-
   // Save files
   for (int level = 0; level < current_->NumberLevels(); level++) {
     const std::vector<FileMetaData*>& files = current_->files_[level];

db/version_set.h

@@ -469,10 +469,6 @@ class VersionSet {
   // we have too many level 0 files
   bool need_slowdown_for_num_level0_files_;
 
-  // Per-level key at which the next compaction at that level should start.
-  // Either an empty string, or a valid InternalKey.
-  std::string* compact_pointer_;
-
   // An object that keeps all the compaction stats
   // and picks the next compaction
   std::unique_ptr<CompactionPicker> compaction_picker_;

db/version_set_reduce_num_levels.cc

@@ -67,9 +67,7 @@ Status VersionSet::ReduceNumberOfLevels(int new_levels, port::Mutex* mu) {
   current_version->files_ = new_files_list;
   current_version->num_levels_ = new_levels;
 
-  delete[] compact_pointer_;
   num_levels_ = new_levels;
-  compact_pointer_ = new std::string[new_levels];
   compaction_picker_->ReduceNumberOfLevels(new_levels);
   VersionEdit ve;
   st = LogAndApply(&ve, mu, true);