Fix the wrong comment of level compaction cf paths test (facebook#8533)

Summary: Pull Request resolved: facebook#8533

Reviewed By: ajkr

Differential Revision: D29718067

fbshipit-source-id: b4b91c9271362e7a7d47ddbaf28f56fb537cc668

db/db_compaction_test.cc

@@ -2332,7 +2332,7 @@ TEST_P(DBCompactionTestWithParam, LevelCompactionCFPathUse) {
   option_vector.emplace_back(DBOptions(options), cf_opt1);
   CreateColumnFamilies({"one"},option_vector[1]);
 
-  // Configura CF2 specific paths.
+  // Configure CF2 specific paths.
   cf_opt2.cf_paths.emplace_back(dbname_ + "cf2", 500 * 1024);
   cf_opt2.cf_paths.emplace_back(dbname_ + "cf2_2", 4 * 1024 * 1024);
   cf_opt2.cf_paths.emplace_back(dbname_ + "cf2_3", 1024 * 1024 * 1024);
@@ -2387,13 +2387,16 @@ TEST_P(DBCompactionTestWithParam, LevelCompactionCFPathUse) {
   // Check that default column family uses db_paths.
   // And Column family "one" uses cf_paths.
 
-  // First three 110KB files are not going to second path.
-  // After that, (100K, 200K)
+  // The compaction in level0 outputs the sst files in level1.
+  // The first path cannot hold level1's data(400KB+400KB > 500KB),
+  // so every compaction move a sst file to second path. Please
+  // refer to LevelCompactionBuilder::GetPathId.
   for (int num = 0; num < 3; num++) {
     generate_file();
   }
+  check_sstfilecount(0, 1);
+  check_sstfilecount(1, 2);
 
-  // Another 110KB triggers a compaction to 400K file to fill up first path
   generate_file();
   check_sstfilecount(1, 3);