Make DBCompactionTestWithParam::CompactionTrigger more deterministic

Summary: Make DBCompactionTestWithParam::CompactionTrigger more deterministic

Test Plan: ./db_compaction_test

Reviewers: anthony, IslamAbdelRahman, rven, kradhakrishnan, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D51507

db/db_compaction_test.cc

@@ -461,16 +461,17 @@ TEST_F(DBCompactionTest, DisableStatsUpdateReopen) {
 
 
 TEST_P(DBCompactionTestWithParam, CompactionTrigger) {
-  int kNumKeysPerFile = 100;
+  const int kNumKeysPerFile = 100;
 
   Options options;
-  options.write_buffer_size = 200 << 10;
+  options.write_buffer_size = 110 << 10;  // 110KB
   options.arena_block_size = 4 << 10;
   options.num_levels = 3;
   options.level0_file_num_compaction_trigger = 3;
   options.max_subcompactions = max_subcompactions_;
   options.memtable_factory.reset(new SpecialSkipListFactory(kNumKeysPerFile));
   options = CurrentOptions(options);
+  options.memtable_factory.reset(new SpecialSkipListFactory(kNumKeysPerFile));
   CreateAndReopenWithCF({"pikachu"}, options);
 
   Random rnd(301);
@@ -483,6 +484,7 @@ TEST_P(DBCompactionTestWithParam, CompactionTrigger) {
       values.push_back(RandomString(&rnd, 990));
       ASSERT_OK(Put(1, Key(i), values[i]));
     }
+    // put extra key to trigger flush
     ASSERT_OK(Put(1, "", ""));
     dbfull()->TEST_WaitForFlushMemTable(handles_[1]);
     ASSERT_EQ(NumTableFilesAtLevel(0, 1), num + 1);
@@ -490,10 +492,12 @@ TEST_P(DBCompactionTestWithParam, CompactionTrigger) {
 
   // generate one more file in level-0, and should trigger level-0 compaction
   std::vector<std::string> values;
-  for (int i = 0; i < 100; i++) {
+  for (int i = 0; i < kNumKeysPerFile; i++) {
     values.push_back(RandomString(&rnd, 990));
     ASSERT_OK(Put(1, Key(i), values[i]));
   }
+  // put extra key to trigger flush
+  ASSERT_OK(Put(1, "", ""));
   dbfull()->TEST_WaitForCompact();
 
   ASSERT_EQ(NumTableFilesAtLevel(0, 1), 0);