Squash this commit with the previous commit if it pass code review

Two new system variables were added:

tokudb_enable_native_patition -
  enable native partitioning for TokuDB, read-only, default value is 'off',
rocksdb_enable_native_patition -
  enable native partitioning for RocksDB, read-only, default value is 'off'.

storage/rocksdb/ha_rocksdb.cc

@@ -471,6 +471,7 @@ static char *rocksdb_strict_collation_exceptions = nullptr;
 static my_bool rocksdb_collect_sst_properties = TRUE;
 static my_bool rocksdb_force_flush_memtable_now_var = FALSE;
 static my_bool rocksdb_force_flush_memtable_and_lzero_now_var = FALSE;
+static my_bool rocksdb_enable_native_partition = FALSE;
 static my_bool rocksdb_enable_ttl = TRUE;
 static my_bool rocksdb_enable_ttl_read_filtering = TRUE;
 static int rocksdb_debug_ttl_rec_ts = 0;
@@ -1300,6 +1301,12 @@ static MYSQL_SYSVAR_BOOL(pause_background_work, rocksdb_pause_background_work,
                          "Disable all rocksdb background operations", nullptr,
                          rocksdb_set_pause_background_work, false);
 
+static MYSQL_SYSVAR_BOOL(
+    enable_native_partition, rocksdb_enable_native_partition,
+    PLUGIN_VAR_READONLY,
+    "Enable native partitioning", nullptr,
+    nullptr, false);
+
 static MYSQL_SYSVAR_BOOL(
     enable_ttl, rocksdb_enable_ttl, PLUGIN_VAR_RQCMDARG,
     "Enable expired TTL records to be dropped during compaction.", nullptr,
@@ -1630,6 +1637,7 @@ static struct st_mysql_sys_var *rocksdb_system_variables[] = {
     MYSQL_SYSVAR(collect_sst_properties),
     MYSQL_SYSVAR(force_flush_memtable_now),
     MYSQL_SYSVAR(force_flush_memtable_and_lzero_now),
+    MYSQL_SYSVAR(enable_native_partition),
     MYSQL_SYSVAR(enable_ttl),
     MYSQL_SYSVAR(enable_ttl_read_filtering),
     MYSQL_SYSVAR(debug_ttl_rec_ts),
@@ -3921,7 +3929,8 @@ static int rocksdb_init_func(void *const p) {
   rocksdb_hton->flags = HTON_TEMPORARY_NOT_SUPPORTED |
                         HTON_SUPPORTS_EXTENDED_KEYS | HTON_CAN_RECREATE;
 
-  rocksdb_hton->partition_flags = rocksdb_partition_flags;
+  if (rocksdb_enable_native_partition)
+    rocksdb_hton->partition_flags = rocksdb_partition_flags;
 
   DBUG_ASSERT(!mysqld_embedded);
 
@@ -4774,7 +4783,8 @@ static handler *rocksdb_create_handler(my_core::handlerton *const hton,
                                        my_core::TABLE_SHARE *const table_arg,
                                        my_core::MEM_ROOT *const mem_root) {
 
-  if (table_arg && table_arg->db_type() == rocksdb_hton &&
+  if (rocksdb_enable_native_partition &&
+      table_arg && table_arg->db_type() == rocksdb_hton &&
       table_arg->partition_info_str && table_arg->partition_info_str_len) {
     ha_rockspart *file = new (mem_root) ha_rockspart(hton, table_arg);
     if (file && file->init_partitioning(mem_root)) {

storage/tokudb/hatoku_hton.cc

@@ -354,7 +354,8 @@ static int tokudb_init_func(void *p) {
 #endif
 
     tokudb_hton->create = tokudb_create_handler;
-    tokudb_hton->partition_flags = tokudb_partition_flags;
+    if (tokudb::sysvars::enable_native_partition)
+        tokudb_hton->partition_flags = tokudb_partition_flags;
     tokudb_hton->close_connection = tokudb_close_connection;
     tokudb_hton->kill_connection = tokudb_kill_connection;
 
@@ -661,7 +662,8 @@ static int tokudb_done_func(TOKUDB_UNUSED(void* p)) {
 static handler* tokudb_create_handler(handlerton* hton,
                                       TABLE_SHARE* table,
                                       MEM_ROOT* mem_root) {
-    if (table && table->db_type() == tokudb_hton && table->partition_info_str &&
+    if (tokudb::sysvars::enable_native_partition &&
+        table && table->db_type() == tokudb_hton && table->partition_info_str &&
         table->partition_info_str_len) {
         ha_tokupart* file = new (mem_root) ha_tokupart(hton, table);
         if (file && file->init_partitioning(mem_root)) {

storage/tokudb/tokudb_sysvars.cc

@@ -63,6 +63,7 @@ ulong       debug = 0;
 my_bool     debug_pause_background_job_manager = FALSE;
 #endif  // defined(TOKUDB_DEBUG) && TOKUDB_DEBUG
 my_bool     directio = FALSE;
+my_bool     enable_native_partition = FALSE;
 my_bool     enable_partial_eviction = TRUE;
 // file system reserve as a percentage of total disk space
 int         fs_reserve_percent = 0;
@@ -263,6 +264,15 @@ static MYSQL_SYSVAR_BOOL(
     NULL,
     FALSE);
 
+static MYSQL_SYSVAR_BOOL(
+    enable_native_partition,
+    enable_native_partition,
+    PLUGIN_VAR_READONLY,
+    "enable native partitioning",
+    NULL,
+    NULL,
+    FALSE);
+
 static void enable_partial_eviction_update(
     TOKUDB_UNUSED(THD* thd),
     TOKUDB_UNUSED(st_mysql_sys_var* sys_var),
@@ -958,6 +968,7 @@ st_mysql_sys_var* system_variables[] = {
     MYSQL_SYSVAR(data_dir),
     MYSQL_SYSVAR(debug),
     MYSQL_SYSVAR(directio),
+    MYSQL_SYSVAR(enable_native_partition),
     MYSQL_SYSVAR(enable_partial_eviction),
     MYSQL_SYSVAR(fs_reserve_percent),
     MYSQL_SYSVAR(fsync_log_period),

storage/tokudb/tokudb_sysvars.h

@@ -72,6 +72,7 @@ extern my_bool      compress_buffers_before_eviction;
 extern char*        data_dir;
 extern ulong        debug;
 extern my_bool      directio;
+extern my_bool      enable_native_partition;
 extern my_bool      enable_partial_eviction;
 extern int          fs_reserve_percent;
 extern uint         fsync_log_period;