[rocksdb] do not trim range for level0 in manual compaction

Summary:
https://code.google.com/p/leveldb/issues/detail?can=1&q=178&colspec=ID%20Type%20Status%20Priority%20Milestone%20Owner%20Summary&id=178

Ported the solution as is to RocksDB.

Test Plan: moved the unit test as manual_compaction_test

Reviewers: dhruba

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D11331

Makefile

@@ -62,7 +62,8 @@ TESTS = \
 	auto_roll_logger_test \
 	filelock_test \
 	merge_test \
-	redis_test
+	redis_test \
+	manual_compaction_test
 
 TOOLS = \
         sst_dump \
@@ -247,6 +248,9 @@ $(MEMENVLIBRARY) : $(MEMENVOBJECTS)
 memenv_test : helpers/memenv/memenv_test.o $(MEMENVLIBRARY) $(LIBRARY) $(TESTHARNESS)
 	$(CXX) helpers/memenv/memenv_test.o $(MEMENVLIBRARY) $(LIBRARY) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
 
+manual_compaction_test: util/manual_compaction_test.o $(LIBOBJECTS) $(TESTHARNESS)
+	$(CXX) util/manual_compaction_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+
 leveldb_shell: tools/shell/ShellContext.o tools/shell/ShellState.o tools/shell/LeveldbShell.o tools/shell/DBClientProxy.o tools/shell/ShellContext.h tools/shell/ShellState.h tools/shell/DBClientProxy.h $(LIBOBJECTS)
 	$(CXX) tools/shell/ShellContext.o tools/shell/ShellState.o tools/shell/LeveldbShell.o tools/shell/DBClientProxy.o $(LIBOBJECTS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
 

db/version_set.cc

@@ -2227,16 +2227,23 @@ Compaction* VersionSet::CompactRange(
     return nullptr;
   }
 
+
   // Avoid compacting too much in one shot in case the range is large.
-  const uint64_t limit = MaxFileSizeForLevel(level) *
+  // But we cannot do this for level-0 since level-0 files can overlap
+  // and we must not pick one file and drop another older file if the
+  // two files overlap.
+  if (level > 0) {
+
+    const uint64_t limit = MaxFileSizeForLevel(level) *
                          options_->source_compaction_factor;
-  uint64_t total = 0;
-  for (size_t i = 0; i < inputs.size(); i++) {
-    uint64_t s = inputs[i]->file_size;
-    total += s;
-    if (total >= limit) {
-      inputs.resize(i + 1);
-      break;
+    uint64_t total = 0;
+    for (size_t i = 0; i < inputs.size(); ++i) {
+      uint64_t s = inputs[i]->file_size;
+      total += s;
+      if (total >= limit) {
+        inputs.resize(i + 1);
+        break;
+      }
     }
   }
 

util/manual_compaction_test.cc

@@ -0,0 +1,88 @@
+// Test for issue 178: a manual compaction causes deleted data to reappear.
+#include <iostream>
+#include <sstream>
+#include <cstdlib>
+
+#include "leveldb/db.h"
+#include "leveldb/write_batch.h"
+#include "util/testharness.h"
+
+namespace {
+
+const int kNumKeys = 1100000;
+
+std::string Key1(int i) {
+  char buf[100];
+  snprintf(buf, sizeof(buf), "my_key_%d", i);
+  return buf;
+}
+
+std::string Key2(int i) {
+  return Key1(i) + "_xxx";
+}
+
+class ManualCompactionTest { };
+
+TEST(ManualCompactionTest, Test) {
+  // Get rid of any state from an old run.
+  std::string dbpath = leveldb::test::TmpDir() + "/leveldb_cbug_test";
+  DestroyDB(dbpath, leveldb::Options());
+
+  // Open database.  Disable compression since it affects the creation
+  // of layers and the code below is trying to test against a very
+  // specific scenario.
+  leveldb::DB* db;
+  leveldb::Options db_options;
+  db_options.create_if_missing = true;
+  db_options.compression = leveldb::kNoCompression;
+  ASSERT_OK(leveldb::DB::Open(db_options, dbpath, &db));
+
+  // create first key range
+  leveldb::WriteBatch batch;
+  for (int i = 0; i < kNumKeys; i++) {
+    batch.Put(Key1(i), "value for range 1 key");
+  }
+  ASSERT_OK(db->Write(leveldb::WriteOptions(), &batch));
+
+  // create second key range
+  batch.Clear();
+  for (int i = 0; i < kNumKeys; i++) {
+    batch.Put(Key2(i), "value for range 2 key");
+  }
+  ASSERT_OK(db->Write(leveldb::WriteOptions(), &batch));
+
+  // delete second key range
+  batch.Clear();
+  for (int i = 0; i < kNumKeys; i++) {
+    batch.Delete(Key2(i));
+  }
+  ASSERT_OK(db->Write(leveldb::WriteOptions(), &batch));
+
+  // compact database
+  std::string start_key = Key1(0);
+  std::string end_key = Key1(kNumKeys - 1);
+  leveldb::Slice least(start_key.data(), start_key.size());
+  leveldb::Slice greatest(end_key.data(), end_key.size());
+
+  // commenting out the line below causes the example to work correctly
+  db->CompactRange(&least, &greatest);
+
+  // count the keys
+  leveldb::Iterator* iter = db->NewIterator(leveldb::ReadOptions());
+  int num_keys = 0;
+  for (iter->SeekToFirst(); iter->Valid(); iter->Next()) {
+    num_keys++;
+  }
+  delete iter;
+  ASSERT_EQ(kNumKeys, num_keys) << "Bad number of keys";
+
+  // close database
+  delete db;
+  DestroyDB(dbpath, leveldb::Options());
+}
+
+}  // anonymous namespace
+
+int main(int argc, char** argv) {
+  return leveldb::test::RunAllTests();
+}