1. Set 1M as the threshold on the number of records to flush the cache.

2. Set 100k as the batch size when flushing records into ColumnStore, i.e.,
a flush of 1M records will be performed in 10 batches, each being 100k.

3. For INSERT ... SELECT on the cache, use the default insertion method of cpimport.

dbcon/mysql/ha_mcs.h

@@ -300,7 +300,7 @@ public:
 
   /* Cache functions */
   void free_locks();
-  bool rows_cached();
+  ha_rows num_rows_cached();
   int flush_insert_cache();
   friend my_bool get_status_and_flush_cache(void *param,
                                             my_bool concurrent_insert);