Implement command to show per-compaction-level compression ratio

src/Commands.cc

@@ -126,6 +126,7 @@ struct cmdMapInit {
     redis_cmd_map["quarkdb_invalid_command"] = {RedisCommand::QUARKDB_INVALID_COMMAND, CommandType::QUARKDB};
     redis_cmd_map["quarkdb_manual_compaction"] = {RedisCommand::QUARKDB_MANUAL_COMPACTION, CommandType::QUARKDB};
     redis_cmd_map["quarkdb_level_stats"] = {RedisCommand::QUARKDB_LEVEL_STATS, CommandType::QUARKDB};
+    redis_cmd_map["quarkdb_compression_stats"] = {RedisCommand::QUARKDB_COMPRESSION_STATS, CommandType::QUARKDB};
 
     redis_cmd_map["recovery_info"] = {RedisCommand::RECOVERY_INFO, CommandType::RECOVERY};
     redis_cmd_map["recovery_set"] = {RedisCommand::RECOVERY_SET, CommandType::RECOVERY};

src/Commands.hh

@@ -128,6 +128,7 @@ enum class RedisCommand {
   QUARKDB_INVALID_COMMAND,                  // used in tests
   QUARKDB_MANUAL_COMPACTION,
   QUARKDB_LEVEL_STATS,
+  QUARKDB_COMPRESSION_STATS,
 
   RECOVERY_GET,
   RECOVERY_SET,

src/Shard.cc

@@ -208,6 +208,21 @@ LinkStatus Shard::dispatch(Connection *conn, RedisRequest &req) {
 
       return conn->status(stateMachine->levelStats());
     }
+    case RedisCommand::QUARKDB_COMPRESSION_STATS: {
+      if(req.size() != 1) return conn->errArgs(req[0]);
+      InFlightRegistration registration(inFlightTracker);
+      if(!registration.ok()) {
+        return conn->err("unavailable");
+      }
+
+      std::ostringstream ss;
+      std::vector<std::string> stats = stateMachine->compressionStats();
+      for(size_t i = 0; i < stats.size(); i++) {
+        ss << "Level " << i << ": " << stats[i] << std::endl;
+      }
+
+      return conn->status(ss.str());
+    }
     default: {
       if(req.getCommandType() == CommandType::QUARKDB) {
         qdb_critical("Unable to dispatch command '" << req[0] << "' of type QUARKDB");

src/StateMachine.cc

@@ -1229,6 +1229,18 @@ std::string StateMachine::levelStats() {
   return stats;
 }
 
+std::vector<std::string> StateMachine::compressionStats() {
+  std::vector<std::string> results;
+
+  for(size_t i = 0; i <= 6; i++) {
+    std::string tmp;
+    db->GetProperty(SSTR(rocksdb::DB::Properties::kCompressionRatioAtLevelPrefix << i), &tmp);
+    results.emplace_back(tmp);
+  }
+
+  return results;
+}
+
 rocksdb::Status StateMachine::noop(LogIndex index) {
   StagingArea stagingArea(*this);
   return stagingArea.commit(index);

src/StateMachine.hh

@@ -173,6 +173,11 @@ public:
   //----------------------------------------------------------------------------
   std::string levelStats();
 
+  //----------------------------------------------------------------------------
+  // Get compression stats
+  //----------------------------------------------------------------------------
+  std::vector<std::string> compressionStats();
+
   bool inBulkLoad() const {
     return bulkLoad;
   }

test/e2e.cc

@@ -937,6 +937,7 @@ TEST_F(Raft_e2e, smove) {
   ASSERT_REPLY(tunnel(leaderID)->exec("smembers", "set2"), make_vec("i1", "t1", "t2", "t3", "t4", "t5"));
   ASSERT_REPLY(tunnel(leaderID)->exec("quarkdb-manual-compaction"), "OK");
   qdb_info(qclient::describeRedisReply(tunnel(leaderID)->exec("quarkdb-level-stats").get()));
+  qdb_info(qclient::describeRedisReply(tunnel(leaderID)->exec("quarkdb-compression-stats").get()));
 }
 
 TEST_F(Raft_e2e, sscan) {