Added back MRR counters. The new names are: Handler_mrr_init,

 Handler_mrr_key_refills, Handler_mrr_rowid_refills.

mysql-test/r/myisam_mrr.result

@@ -563,6 +563,9 @@ drop table t1;
 flush status;
 show status like 'Handler_mrr%';
 Variable_name	Value
+Handler_mrr_init	0
+Handler_mrr_key_refills	0
+Handler_mrr_rowid_refills	0
 create table t0 (a int);
 insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
 create table t1 (a int, b int, filler char(200), key(a));
@@ -578,6 +581,9 @@ sum(b)
 1230
 show status like 'handler_mrr%';
 Variable_name	Value
+Handler_mrr_init	1
+Handler_mrr_key_refills	0
+Handler_mrr_rowid_refills	0
 set @mrr_buffer_size_save= @@mrr_buffer_size;
 set mrr_buffer_size=128;
 explain select sum(b) from t1 where a < 1600;
@@ -590,6 +596,9 @@ sum(b)
 196800
 show status like 'handler_mrr%';
 Variable_name	Value
+Handler_mrr_init	1
+Handler_mrr_key_refills	0
+Handler_mrr_rowid_refills	1
 set @@mrr_buffer_size= @mrr_buffer_size_save;
 #Now, let's check BKA: 
 set @join_cache_level_save= @@join_cache_level;
@@ -605,6 +614,9 @@ sum(t1.b)
 1230
 show status like 'handler_mrr%';
 Variable_name	Value
+Handler_mrr_init	1
+Handler_mrr_key_refills	0
+Handler_mrr_rowid_refills	0
 set join_buffer_size=10;
 explain select sum(t1.b) from t0,t1 where t0.a=t1.a;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
@@ -616,6 +628,9 @@ sum(t1.b)
 1230
 show status like 'handler_mrr%';
 Variable_name	Value
+Handler_mrr_init	1or2
+Handler_mrr_key_refills	1or2
+Handler_mrr_rowid_refills	1or2
 set join_cache_level= @join_cache_level_save;
 set join_buffer_size= @join_buffer_size_save;
 drop table t0, t1;

mysql-test/r/status.result

@@ -277,6 +277,9 @@ Handler_delete	0
 Handler_discover	0
 Handler_icp_attempts 	0
 Handler_icp_match	0
+Handler_mrr_init	0
+Handler_mrr_key_refills	0
+Handler_mrr_rowid_refills	0
 Handler_prepare	0
 Handler_read_first	0
 Handler_read_key	4
@@ -299,7 +302,7 @@ Created_tmp_files	0
 Created_tmp_tables	2
 Handler_tmp_update	2
 Handler_tmp_write	7
-Rows_tmp_read	37
+Rows_tmp_read	40
 drop table t1;
 CREATE TABLE t1 (i int(11) DEFAULT NULL, KEY i (i) ) ENGINE=MyISAM;
 insert into t1 values (1),(2),(3),(4),(5);
@@ -314,6 +317,9 @@ Handler_delete	0
 Handler_discover	0
 Handler_icp_attempts 	0
 Handler_icp_match	0
+Handler_mrr_init	0
+Handler_mrr_key_refills	0
+Handler_mrr_rowid_refills	0
 Handler_prepare	0
 Handler_read_first	0
 Handler_read_key	2

mysql-test/r/status_user.result

@@ -102,6 +102,9 @@ Handler_delete	1
 Handler_discover	0
 Handler_icp_attempts 	0
 Handler_icp_match	0
+Handler_mrr_init	0
+Handler_mrr_key_refills	0
+Handler_mrr_rowid_refills	0
 Handler_prepare	18
 Handler_read_first	0
 Handler_read_key	3

sql/multi_range_read.cc

@@ -510,7 +510,7 @@ int Mrr_ordered_index_reader::refill_buffer(bool initial)
   {
     /* This is a non-initial buffer fill and we've got a non-empty buffer */
     THD *thd= current_thd;
-    status_var_increment(thd->status_var.ha_mrr_extra_key_sorts);
+    status_var_increment(thd->status_var.ha_mrr_key_refills_count);
   }
 
   key_buffer->sort((key_buffer->type() == Lifo_buffer::FORWARD)? 
@@ -610,7 +610,7 @@ int Mrr_ordered_rndpos_reader::refill_buffer(bool initial)
   {
     /* Ok, this was a successful buffer refill operation */
     THD *thd= current_thd;
-    status_var_increment(thd->status_var.ha_mrr_extra_rowid_sorts);
+    status_var_increment(thd->status_var.ha_mrr_rowid_refills_count);
   }
 
   DBUG_RETURN(res);
@@ -845,8 +845,6 @@ int DsMrr_impl::dsmrr_init(handler *h_arg, RANGE_SEQ_IF *seq_funcs,
     strategy= disk_strategy= &reader_factory.ordered_rndpos_reader;
   }
 
-  status_var_increment(thd->status_var.ha_multi_range_read_init_count);
-
   full_buf= buf->buffer;
   full_buf_end= buf->buffer_end;
 
@@ -936,6 +934,12 @@ int DsMrr_impl::dsmrr_init(handler *h_arg, RANGE_SEQ_IF *seq_funcs,
       goto error;
     }
   }
+  
+  /* 
+    At this point, we're sure that we're running a native MRR scan (i.e. we
+    didnt fall back to default implementation for some reason).
+  */
+  status_var_increment(thd->status_var.ha_mrr_init_count);
 
   res= strategy->refill_buffer(TRUE);
   if (res)

sql/mysqld.cc

@@ -8101,12 +8101,11 @@ SHOW_VAR status_vars[]= {
   {"Handler_commit",           (char*) offsetof(STATUS_VAR, ha_commit_count), SHOW_LONG_STATUS},
   {"Handler_delete",           (char*) offsetof(STATUS_VAR, ha_delete_count), SHOW_LONG_STATUS},
   {"Handler_discover",         (char*) offsetof(STATUS_VAR, ha_discover_count), SHOW_LONG_STATUS},
-#if 0
-  /* Made 3 counters below temporarily invisible until we agree upon their names */
-  {"Handler_mrr_extra_key_sorts",   (char*) offsetof(STATUS_VAR, ha_mrr_extra_key_sorts), SHOW_LONG_STATUS},
-  {"Handler_mrr_extra_rowid_sorts", (char*) offsetof(STATUS_VAR, ha_mrr_extra_rowid_sorts), SHOW_LONG_STATUS},
-  {"Handler_mrr_init",         (char*) offsetof(STATUS_VAR, ha_multi_range_read_init_count),  SHOW_LONG_STATUS},
-#endif
+
+  {"Handler_mrr_key_refills",   (char*) offsetof(STATUS_VAR, ha_mrr_key_refills_count), SHOW_LONG_STATUS},
+  {"Handler_mrr_rowid_refills", (char*) offsetof(STATUS_VAR, ha_mrr_rowid_refills_count), SHOW_LONG_STATUS},
+  {"Handler_mrr_init",         (char*) offsetof(STATUS_VAR, ha_mrr_init_count),  SHOW_LONG_STATUS},
+
   {"Handler_icp_attempts ",    (char*) offsetof(STATUS_VAR, ha_icp_attempts), SHOW_LONG_STATUS},
   {"Handler_icp_match",        (char*) offsetof(STATUS_VAR, ha_icp_match), SHOW_LONG_STATUS},
   {"Handler_prepare",          (char*) offsetof(STATUS_VAR, ha_prepare_count),  SHOW_LONG_STATUS},

sql/sql_class.h

@@ -577,9 +577,9 @@ typedef struct system_status_var
     calls made by range access. The intent is to count only calls made by
     BatchedKeyAccess.
   */
-  ulong ha_multi_range_read_init_count;
-  ulong ha_mrr_extra_key_sorts;
-  ulong ha_mrr_extra_rowid_sorts;
+  ulong ha_mrr_init_count;
+  ulong ha_mrr_key_refills_count;
+  ulong ha_mrr_rowid_refills_count;
 
   ulong ha_rollback_count;
   ulong ha_update_count;