Double insert performance by reusing the prepared insert statement.

Related to ticket #29.

DCDBLib/include_internal/cassandraBackend.h

@@ -34,6 +34,8 @@ protected:
   const CassSchema*  schema;    /**< The schema object containing the current database schema information */
   std::string  currentKeyspace; /**< The name of the active keyspace */
 
+  const CassPrepared* preparedInsert; /**< The prepared statement for insertions */
+
   /**
    * @brief This function validates a name to ensure that
    *        it only consists of alphanumeric characters.
@@ -135,6 +137,11 @@ public:
    */
   void insert(std::string key, uint64_t ts, uint64_t value);
 
+  /**
+   * @brief Prepare for insertions
+   */
+  void prepareInsert();
+
 
   /* Class constructor / desctructor */
 

DCDBLib/src/cassandraBackend.cpp

@@ -263,23 +263,9 @@ void CassandraBackend::insert(std::string key, uint64_t ts, uint64_t value)
 #endif
     CassError rc = CASS_OK;
     CassStatement* statement = NULL;
-    CassFuture* future = NULL;
-    const CassPrepared* prepared = NULL;
-    CassString query = cass_string_init("INSERT INTO dcdb.sensordata (sid, ts, value) VALUES (?, ?, ?);");
+    CassFuture *future = NULL;
 
-    future = cass_session_prepare(session, query);
-    cass_future_wait(future);
-
-    rc = cass_future_error_code(future);
-    if (rc != CASS_OK) {
-        printError(future);
-    } else {
-        prepared = cass_future_get_prepared(future);
-    }
-
-    cass_future_free(future);
-
-    statement = cass_prepared_bind(prepared);
+    statement = cass_prepared_bind(preparedInsert);
 
     CassBytes sid = cass_bytes_init((cass_byte_t*)(key.c_str()), 16);
 
@@ -296,11 +282,35 @@ void CassandraBackend::insert(std::string key, uint64_t ts, uint64_t value)
         printError(future);
     }
 
-    cass_prepared_free(prepared);
     cass_future_free(future);
     cass_statement_free(statement);
 }
 
+/**
+ * @details
+ * Since we want high-performance inserts, we prepare the
+ * insert CQL query in advance and only bind it on the actual
+ * insert.
+ */
+void CassandraBackend::prepareInsert()
+{
+  CassError rc = CASS_OK;
+  CassFuture* future = NULL;
+  CassString query = cass_string_init("INSERT INTO dcdb.sensordata (sid, ts, value) VALUES (?, ?, ?);");
+
+  future = cass_session_prepare(session, query);
+  cass_future_wait(future);
+
+  rc = cass_future_error_code(future);
+  if (rc != CASS_OK) {
+      printError(future);
+  } else {
+      preparedInsert = cass_future_get_prepared(future);
+  }
+
+  cass_future_free(future);
+}
+
 CassandraBackend::CassandraBackend()
 {
   cluster = nullptr;
@@ -311,6 +321,8 @@ CassandraBackend::CassandraBackend()
 CassandraBackend::~CassandraBackend()
 {
   /* Clean up... */
+  if (preparedInsert)
+    cass_prepared_free(preparedInsert);
   if (session)
     cass_session_free(session);
   if (cluster)

DCDBLib/src/sensordatastore.cpp

@@ -150,6 +150,9 @@ void SensorDataStoreImpl::init(std::string hostname, int port) {
           "sid, ts",
           "COMPACT STORAGE");
   }
+
+  /* Prepare for optimized insertions */
+  csBackend->prepareInsert();
 }
 
 /**