A number of fixes:

- Replace raw slice comparison with a call to user comparator.
  Added test for custom comparators.

- Fix end of namespace comments.

- Fixed bug in picking inputs for a level-0 compaction.

  When finding overlapping files, the covered range may expand
  as files are added to the input set.  We now correctly expand
  the range when this happens instead of continuing to use the
  old range.  For example, suppose L0 contains files with the
  following ranges:

      F1: a .. d
      F2:    c .. g
      F3:       f .. j

  and the initial compaction target is F3.  We used to search
  for range f..j which yielded {F2,F3}.  However we now expand
  the range as soon as another file is added.  In this case,
  when F2 is added, we expand the range to c..j and restart the
  search.  That picks up file F1 as well.

  This change fixes a bug related to deleted keys showing up
  incorrectly after a compaction as described in Issue 44.

(Sync with upstream @25072954)

Author: zmodem

db/builder.cc

@@ -85,4 +85,4 @@ Status BuildTable(const std::string& dbname,
   return s;
 }
 
-}
+}  // namespace leveldb

db/builder.h

@@ -29,6 +29,6 @@ extern Status BuildTable(const std::string& dbname,
                          Iterator* iter,
                          FileMetaData* meta);
 
-}
+}  // namespace leveldb
 
 #endif  // STORAGE_LEVELDB_DB_BUILDER_H_

db/corruption_test.cc

@@ -352,7 +352,7 @@ TEST(CorruptionTest, UnrelatedKeys) {
   ASSERT_EQ(Value(1000, &tmp2).ToString(), v);
 }
 
-}
+}  // namespace leveldb
 
 int main(int argc, char** argv) {
   return leveldb::test::RunAllTests();

db/db_bench.cc

@@ -288,7 +288,7 @@ struct ThreadState {
   }
 };
 
-}
+}  // namespace
 
 class Benchmark {
  private:
@@ -829,7 +829,7 @@ class Benchmark {
   }
 };
 
-}
+}  // namespace leveldb
 
 int main(int argc, char** argv) {
   FLAGS_write_buffer_size = leveldb::Options().write_buffer_size;

db/db_impl.cc

@@ -985,7 +985,7 @@ static void CleanupIteratorState(void* arg1, void* arg2) {
   state->mu->Unlock();
   delete state;
 }
-}
+}  // namespace
 
 Iterator* DBImpl::NewInternalIterator(const ReadOptions& options,
                                       SequenceNumber* latest_snapshot) {
@@ -1378,4 +1378,4 @@ Status DestroyDB(const std::string& dbname, const Options& options) {
   return result;
 }
 
-}
+}  // namespace leveldb

db/db_impl.h

@@ -187,6 +187,6 @@ extern Options SanitizeOptions(const std::string& db,
                                const InternalKeyComparator* icmp,
                                const Options& src);
 
-}
+}  // namespace leveldb
 
 #endif  // STORAGE_LEVELDB_DB_DB_IMPL_H_

db/db_iter.cc

@@ -296,4 +296,4 @@ Iterator* NewDBIterator(
   return new DBIter(dbname, env, user_key_comparator, internal_iter, sequence);
 }
 
-}
+}  // namespace leveldb

db/db_iter.h

@@ -21,6 +21,6 @@ extern Iterator* NewDBIterator(
     Iterator* internal_iter,
     const SequenceNumber& sequence);
 
-}
+}  // namespace leveldb
 
 #endif  // STORAGE_LEVELDB_DB_DB_ITER_H_

db/db_test.cc

@@ -136,6 +136,33 @@ class DBTest {
     return result;
   }
 
+  // Return a string that contains all key,value pairs in order,
+  // formatted like "(k1->v1)(k2->v2)".
+  std::string Contents() {
+    std::vector<std::string> forward;
+    std::string result;
+    Iterator* iter = db_->NewIterator(ReadOptions());
+    for (iter->SeekToFirst(); iter->Valid(); iter->Next()) {
+      std::string s = IterStatus(iter);
+      result.push_back('(');
+      result.append(s);
+      result.push_back(')');
+      forward.push_back(s);
+    }
+
+    // Check reverse iteration results are the reverse of forward results
+    int matched = 0;
+    for (iter->SeekToLast(); iter->Valid(); iter->Prev()) {
+      ASSERT_LT(matched, forward.size());
+      ASSERT_EQ(IterStatus(iter), forward[forward.size() - matched - 1]);
+      matched++;
+    }
+    ASSERT_EQ(matched, forward.size());
+
+    delete iter;
+    return result;
+  }
+
   std::string AllEntriesFor(const Slice& user_key) {
     Iterator* iter = dbfull()->TEST_NewInternalIterator();
     InternalKey target(user_key, kMaxSequenceNumber, kTypeValue);
@@ -1048,6 +1075,49 @@ TEST(DBTest, OverlapInLevel0) {
   ASSERT_EQ("NOT_FOUND", Get("600"));
 }
 
+TEST(DBTest, L0_CompactionBug_Issue44_a) {
+ Reopen();
+ ASSERT_OK(Put("b", "v"));
+ Reopen();
+ ASSERT_OK(Delete("b"));
+ ASSERT_OK(Delete("a"));
+ Reopen();
+ ASSERT_OK(Delete("a"));
+ Reopen();
+ ASSERT_OK(Put("a", "v"));
+ Reopen();
+ Reopen();
+ ASSERT_EQ("(a->v)", Contents());
+ env_->SleepForMicroseconds(1000000);  // Wait for compaction to finish
+ ASSERT_EQ("(a->v)", Contents());
+}
+
+TEST(DBTest, L0_CompactionBug_Issue44_b) {
+ Reopen();
+ Put("","");
+ Reopen();
+ Delete("e");
+ Put("","");
+ Reopen();
+ Put("c", "cv");
+ Reopen();
+ Put("","");
+ Reopen();
+ Put("","");
+ env_->SleepForMicroseconds(1000000);  // Wait for compaction to finish
+ Reopen();
+ Put("d","dv");
+ Reopen();
+ Put("","");
+ Reopen();
+ Delete("d");
+ Delete("b");
+ Reopen();
+ ASSERT_EQ("(->)(c->cv)", Contents());
+ env_->SleepForMicroseconds(1000000);  // Wait for compaction to finish
+ ASSERT_EQ("(->)(c->cv)", Contents());
+}
+
 TEST(DBTest, ComparatorCheck) {
   class NewComparator : public Comparator {
    public:
@@ -1071,6 +1141,34 @@ TEST(DBTest, ComparatorCheck) {
       << s.ToString();
 }
 
+TEST(DBTest, CustomComparator) {
+  class NumberComparator : public Comparator {
+   public:
+    virtual const char* Name() const { return "test.NumberComparator"; }
+    virtual int Compare(const Slice& a, const Slice& b) const {
+      return (strtol(a.ToString().c_str(), NULL, 0) -
+              strtol(b.ToString().c_str(), NULL, 0));
+    }
+    virtual void FindShortestSeparator(std::string* s, const Slice& l) const {}
+    virtual void FindShortSuccessor(std::string* key) const {}
+  };
+  NumberComparator cmp;
+  Options new_options;
+  new_options.create_if_missing = true;
+  new_options.comparator = &cmp;
+  DestroyAndReopen(&new_options);
+  ASSERT_OK(Put("10", "ten"));
+  ASSERT_OK(Put("0x14", "twenty"));
+  for (int i = 0; i < 2; i++) {
+    ASSERT_EQ("ten", Get("10"));
+    ASSERT_EQ("ten", Get("0xa"));
+    ASSERT_EQ("twenty", Get("20"));
+    ASSERT_EQ("twenty", Get("0x14"));
+    Compact("0", "9999");
+    fprintf(stderr, "ss\n%s\n", DumpSSTableList().c_str());
+  }
+}
+
 TEST(DBTest, ManualCompaction) {
   ASSERT_EQ(config::kMaxMemCompactLevel, 2)
       << "Need to update this test to match kMaxMemCompactLevel";
@@ -1207,7 +1305,7 @@ static void MTThreadBody(void* arg) {
   fprintf(stderr, "... stopping thread %d after %d ops\n", t->id, int(counter));
 }
 
-}
+}  // namespace
 
 TEST(DBTest, MultiThreaded) {
   // Initialize state
@@ -1525,7 +1623,7 @@ void BM_LogAndApply(int iters, int num_base_files) {
           buf, iters, us, ((float)us) / iters);
 }
 
-}
+}  // namespace leveldb
 
 int main(int argc, char** argv) {
   if (argc > 1 && std::string(argv[1]) == "--benchmark") {

db/dbformat.cc

@@ -115,4 +115,4 @@ LookupKey::LookupKey(const Slice& user_key, SequenceNumber s) {
   end_ = dst;
 }
 
-}
+}  // namespace leveldb