Two-sweeps read index_merge plus several small index_merge fixes and improvements

mysql-test/r/index_merge_bdb.result

+drop table if exists t1;
+create table t1 (
+pk int primary key,
+key1 int,
+key2 int,  
+filler char(200),
+filler2 char(200),  
+index(key1),
+index(key2),  
+) type=bdb;
+select * from t1 where (key1 >= 2 and key1 <= 10) or (pk >= 4 and pk <=8 );
+pk	key1	key2	filler	filler2
+2	2	2	filler-data	filler-data-2
+3	3	3	filler-data	filler-data-2
+9	9	9	filler-data	filler-data-2
+10	10	10	filler-data	filler-data-2
+4	4	4	filler-data	filler-data-2
+5	5	5	filler-data	filler-data-2
+6	6	6	filler-data	filler-data-2
+7	7	7	filler-data	filler-data-2
+8	8	8	filler-data	filler-data-2
+set @maxv=1000;
+select * from t1 where 
+(pk < 5) or (pk > 10 and pk < 15) or (pk >= 50 and pk < 55 ) or (pk > @maxv-10) 
+or key1=18 or key1=60;
+pk	key1	key2	filler	filler2
+18	18	18	filler-data	filler-data-2
+60	60	60	filler-data	filler-data-2
+1	1	1	filler-data	filler-data-2
+2	2	2	filler-data	filler-data-2
+3	3	3	filler-data	filler-data-2
+4	4	4	filler-data	filler-data-2
+11	11	11	filler-data	filler-data-2
+12	12	12	filler-data	filler-data-2
+13	13	13	filler-data	filler-data-2
+14	14	14	filler-data	filler-data-2
+50	50	50	filler-data	filler-data-2
+51	51	51	filler-data	filler-data-2
+52	52	52	filler-data	filler-data-2
+53	53	53	filler-data	filler-data-2
+54	54	54	filler-data	filler-data-2
+991	991	991	filler-data	filler-data-2
+992	992	992	filler-data	filler-data-2
+993	993	993	filler-data	filler-data-2
+994	994	994	filler-data	filler-data-2
+995	995	995	filler-data	filler-data-2
+996	996	996	filler-data	filler-data-2
+997	997	997	filler-data	filler-data-2
+998	998	998	filler-data	filler-data-2
+999	999	999	filler-data	filler-data-2
+1000	1000	1000	filler-data	filler-data-2
+select * from t1 where 
+(pk < 5) or (pk > 10 and pk < 15) or (pk >= 50 and pk < 55 ) or (pk > @maxv-10) 
+or key1 < 3 or key1 > @maxv-11;
+pk	key1	key2	filler	filler2
+990	990	990	filler-data	filler-data-2
+1	1	1	filler-data	filler-data-2
+2	2	2	filler-data	filler-data-2
+3	3	3	filler-data	filler-data-2
+4	4	4	filler-data	filler-data-2
+11	11	11	filler-data	filler-data-2
+12	12	12	filler-data	filler-data-2
+13	13	13	filler-data	filler-data-2
+14	14	14	filler-data	filler-data-2
+50	50	50	filler-data	filler-data-2
+51	51	51	filler-data	filler-data-2
+52	52	52	filler-data	filler-data-2
+53	53	53	filler-data	filler-data-2
+54	54	54	filler-data	filler-data-2
+991	991	991	filler-data	filler-data-2
+992	992	992	filler-data	filler-data-2
+993	993	993	filler-data	filler-data-2
+994	994	994	filler-data	filler-data-2
+995	995	995	filler-data	filler-data-2
+996	996	996	filler-data	filler-data-2
+997	997	997	filler-data	filler-data-2
+998	998	998	filler-data	filler-data-2
+999	999	999	filler-data	filler-data-2
+1000	1000	1000	filler-data	filler-data-2
+select * from t1 where 
+(pk < 5) or (pk > 10 and pk < 15) or (pk >= 50 and pk < 55 ) or (pk > @maxv-10) 
+or
+(key1 < 5) or (key1 > 10 and key1 < 15) or (key1 >= 50 and key1 < 55 ) or (key1 > @maxv-10);
+pk	key1	key2	filler	filler2
+1	1	1	filler-data	filler-data-2
+2	2	2	filler-data	filler-data-2
+3	3	3	filler-data	filler-data-2
+4	4	4	filler-data	filler-data-2
+11	11	11	filler-data	filler-data-2
+12	12	12	filler-data	filler-data-2
+13	13	13	filler-data	filler-data-2
+14	14	14	filler-data	filler-data-2
+50	50	50	filler-data	filler-data-2
+51	51	51	filler-data	filler-data-2
+52	52	52	filler-data	filler-data-2
+53	53	53	filler-data	filler-data-2
+54	54	54	filler-data	filler-data-2
+991	991	991	filler-data	filler-data-2
+992	992	992	filler-data	filler-data-2
+993	993	993	filler-data	filler-data-2
+994	994	994	filler-data	filler-data-2
+995	995	995	filler-data	filler-data-2
+996	996	996	filler-data	filler-data-2
+997	997	997	filler-data	filler-data-2
+998	998	998	filler-data	filler-data-2
+999	999	999	filler-data	filler-data-2
+1000	1000	1000	filler-data	filler-data-2
+select * from t1 where 
+(pk > 10 and pk < 15) or (pk >= 50 and pk < 55 )
+or
+(key1 < 5) or (key1 > @maxv-10);
+pk	key1	key2	filler	filler2
+1	1	1	filler-data	filler-data-2
+2	2	2	filler-data	filler-data-2
+3	3	3	filler-data	filler-data-2
+4	4	4	filler-data	filler-data-2
+991	991	991	filler-data	filler-data-2
+992	992	992	filler-data	filler-data-2
+993	993	993	filler-data	filler-data-2
+994	994	994	filler-data	filler-data-2
+995	995	995	filler-data	filler-data-2
+996	996	996	filler-data	filler-data-2
+997	997	997	filler-data	filler-data-2
+998	998	998	filler-data	filler-data-2
+999	999	999	filler-data	filler-data-2
+1000	1000	1000	filler-data	filler-data-2
+11	11	11	filler-data	filler-data-2
+12	12	12	filler-data	filler-data-2
+13	13	13	filler-data	filler-data-2
+14	14	14	filler-data	filler-data-2
+50	50	50	filler-data	filler-data-2
+51	51	51	filler-data	filler-data-2
+52	52	52	filler-data	filler-data-2
+53	53	53	filler-data	filler-data-2
+54	54	54	filler-data	filler-data-2
+drop table t1;

mysql-test/r/index_merge_innodb2.result

+drop table if exists t1;
+create table t1 (
+pk int primary key,
+key1 int,
+key2 int,  
+filler char(200),
+filler2 char(200),  
+index(key1),
+index(key2),  
+) type=innodb;
+select * from t1 where (key1 >= 2 and key1 <= 10) or (pk >= 4 and pk <=8 );
+pk	key1	key2	filler	filler2
+2	2	2	filler-data	filler-data-2
+3	3	3	filler-data	filler-data-2
+9	9	9	filler-data	filler-data-2
+10	10	10	filler-data	filler-data-2
+4	4	4	filler-data	filler-data-2
+5	5	5	filler-data	filler-data-2
+6	6	6	filler-data	filler-data-2
+7	7	7	filler-data	filler-data-2
+8	8	8	filler-data	filler-data-2
+set @maxv=1000;
+select * from t1 where 
+(pk < 5) or (pk > 10 and pk < 15) or (pk >= 50 and pk < 55 ) or (pk > @maxv-10) 
+or key1=18 or key1=60;
+pk	key1	key2	filler	filler2
+18	18	18	filler-data	filler-data-2
+60	60	60	filler-data	filler-data-2
+1	1	1	filler-data	filler-data-2
+2	2	2	filler-data	filler-data-2
+3	3	3	filler-data	filler-data-2
+4	4	4	filler-data	filler-data-2
+11	11	11	filler-data	filler-data-2
+12	12	12	filler-data	filler-data-2
+13	13	13	filler-data	filler-data-2
+14	14	14	filler-data	filler-data-2
+50	50	50	filler-data	filler-data-2
+51	51	51	filler-data	filler-data-2
+52	52	52	filler-data	filler-data-2
+53	53	53	filler-data	filler-data-2
+54	54	54	filler-data	filler-data-2
+991	991	991	filler-data	filler-data-2
+992	992	992	filler-data	filler-data-2
+993	993	993	filler-data	filler-data-2
+994	994	994	filler-data	filler-data-2
+995	995	995	filler-data	filler-data-2
+996	996	996	filler-data	filler-data-2
+997	997	997	filler-data	filler-data-2
+998	998	998	filler-data	filler-data-2
+999	999	999	filler-data	filler-data-2
+1000	1000	1000	filler-data	filler-data-2
+select * from t1 where 
+(pk < 5) or (pk > 10 and pk < 15) or (pk >= 50 and pk < 55 ) or (pk > @maxv-10) 
+or key1 < 3 or key1 > @maxv-11;
+pk	key1	key2	filler	filler2
+990	990	990	filler-data	filler-data-2
+1	1	1	filler-data	filler-data-2
+2	2	2	filler-data	filler-data-2
+3	3	3	filler-data	filler-data-2
+4	4	4	filler-data	filler-data-2
+11	11	11	filler-data	filler-data-2
+12	12	12	filler-data	filler-data-2
+13	13	13	filler-data	filler-data-2
+14	14	14	filler-data	filler-data-2
+50	50	50	filler-data	filler-data-2
+51	51	51	filler-data	filler-data-2
+52	52	52	filler-data	filler-data-2
+53	53	53	filler-data	filler-data-2
+54	54	54	filler-data	filler-data-2
+991	991	991	filler-data	filler-data-2
+992	992	992	filler-data	filler-data-2
+993	993	993	filler-data	filler-data-2
+994	994	994	filler-data	filler-data-2
+995	995	995	filler-data	filler-data-2
+996	996	996	filler-data	filler-data-2
+997	997	997	filler-data	filler-data-2
+998	998	998	filler-data	filler-data-2
+999	999	999	filler-data	filler-data-2
+1000	1000	1000	filler-data	filler-data-2
+select * from t1 where 
+(pk < 5) or (pk > 10 and pk < 15) or (pk >= 50 and pk < 55 ) or (pk > @maxv-10) 
+or
+(key1 < 5) or (key1 > 10 and key1 < 15) or (key1 >= 50 and key1 < 55 ) or (key1 > @maxv-10);
+pk	key1	key2	filler	filler2
+1	1	1	filler-data	filler-data-2
+2	2	2	filler-data	filler-data-2
+3	3	3	filler-data	filler-data-2
+4	4	4	filler-data	filler-data-2
+11	11	11	filler-data	filler-data-2
+12	12	12	filler-data	filler-data-2
+13	13	13	filler-data	filler-data-2
+14	14	14	filler-data	filler-data-2
+50	50	50	filler-data	filler-data-2
+51	51	51	filler-data	filler-data-2
+52	52	52	filler-data	filler-data-2
+53	53	53	filler-data	filler-data-2
+54	54	54	filler-data	filler-data-2
+991	991	991	filler-data	filler-data-2
+992	992	992	filler-data	filler-data-2
+993	993	993	filler-data	filler-data-2
+994	994	994	filler-data	filler-data-2
+995	995	995	filler-data	filler-data-2
+996	996	996	filler-data	filler-data-2
+997	997	997	filler-data	filler-data-2
+998	998	998	filler-data	filler-data-2
+999	999	999	filler-data	filler-data-2
+1000	1000	1000	filler-data	filler-data-2
+select * from t1 where 
+(pk > 10 and pk < 15) or (pk >= 50 and pk < 55 )
+or
+(key1 < 5) or (key1 > @maxv-10);
+pk	key1	key2	filler	filler2
+1	1	1	filler-data	filler-data-2
+2	2	2	filler-data	filler-data-2
+3	3	3	filler-data	filler-data-2
+4	4	4	filler-data	filler-data-2
+991	991	991	filler-data	filler-data-2
+992	992	992	filler-data	filler-data-2
+993	993	993	filler-data	filler-data-2
+994	994	994	filler-data	filler-data-2
+995	995	995	filler-data	filler-data-2
+996	996	996	filler-data	filler-data-2
+997	997	997	filler-data	filler-data-2
+998	998	998	filler-data	filler-data-2
+999	999	999	filler-data	filler-data-2
+1000	1000	1000	filler-data	filler-data-2
+11	11	11	filler-data	filler-data-2
+12	12	12	filler-data	filler-data-2
+13	13	13	filler-data	filler-data-2
+14	14	14	filler-data	filler-data-2
+50	50	50	filler-data	filler-data-2
+51	51	51	filler-data	filler-data-2
+52	52	52	filler-data	filler-data-2
+53	53	53	filler-data	filler-data-2
+54	54	54	filler-data	filler-data-2
+drop table t1;

mysql-test/t/index_merge_bdb.test

+#
+# 2-sweeps read Index_merge test
+#
+-- source include/have_bdb.inc
+
+--disable_warnings
+drop table if exists t1;
+--enable_warnings
+
+create table t1 (
+  pk int primary key,
+  key1 int,
+  key2 int,  
+  filler char(200),
+  filler2 char(200),  
+  index(key1),
+  index(key2),  
+) type=bdb;
+
+
+--disable_query_log
+let $1=1000;
+while ($1)
+{
+  eval insert into t1 values($1, $1, $1, 'filler-data','filler-data-2');
+  dec $1;
+}
+--enable_query_log
+
+select * from t1 where (key1 >= 2 and key1 <= 10) or (pk >= 4 and pk <=8 );
+
+set @maxv=1000;
+
+select * from t1 where 
+  (pk < 5) or (pk > 10 and pk < 15) or (pk >= 50 and pk < 55 ) or (pk > @maxv-10) 
+  or key1=18 or key1=60;
+
+select * from t1 where 
+  (pk < 5) or (pk > 10 and pk < 15) or (pk >= 50 and pk < 55 ) or (pk > @maxv-10) 
+  or key1 < 3 or key1 > @maxv-11;
+
+select * from t1 where 
+  (pk < 5) or (pk > 10 and pk < 15) or (pk >= 50 and pk < 55 ) or (pk > @maxv-10) 
+  or
+  (key1 < 5) or (key1 > 10 and key1 < 15) or (key1 >= 50 and key1 < 55 ) or (key1 > @maxv-10);
+
+select * from t1 where 
+  (pk > 10 and pk < 15) or (pk >= 50 and pk < 55 )
+  or
+  (key1 < 5) or (key1 > @maxv-10);
+
+drop table t1;

mysql-test/t/index_merge_innodb2.test

+#
+# 2-sweeps read Index_merge test
+#
+-- source include/have_innodb.inc
+
+--disable_warnings
+drop table if exists t1;
+--enable_warnings
+
+create table t1 (
+  pk int primary key,
+  key1 int,
+  key2 int,  
+  filler char(200),
+  filler2 char(200),  
+  index(key1),
+  index(key2),  
+) type=innodb;
+
+
+--disable_query_log
+let $1=1000;
+while ($1)
+{
+  eval insert into t1 values($1, $1, $1, 'filler-data','filler-data-2');
+  dec $1;
+}
+--enable_query_log
+
+select * from t1 where (key1 >= 2 and key1 <= 10) or (pk >= 4 and pk <=8 );
+
+set @maxv=1000;
+
+select * from t1 where 
+  (pk < 5) or (pk > 10 and pk < 15) or (pk >= 50 and pk < 55 ) or (pk > @maxv-10) 
+  or key1=18 or key1=60;
+
+select * from t1 where 
+  (pk < 5) or (pk > 10 and pk < 15) or (pk >= 50 and pk < 55 ) or (pk > @maxv-10) 
+  or key1 < 3 or key1 > @maxv-11;
+
+select * from t1 where 
+  (pk < 5) or (pk > 10 and pk < 15) or (pk >= 50 and pk < 55 ) or (pk > @maxv-10) 
+  or
+  (key1 < 5) or (key1 > 10 and key1 < 15) or (key1 >= 50 and key1 < 55 ) or (key1 > @maxv-10);
+
+select * from t1 where 
+  (pk > 10 and pk < 15) or (pk >= 50 and pk < 55 )
+  or
+  (key1 < 5) or (key1 > @maxv-10);
+
+drop table t1;

sql/filesort.cc

@@ -87,9 +87,15 @@ ha_rows filesort(THD *thd, TABLE *table, SORT_FIELD *sortorder, uint s_length,
   DBUG_PUSH("");		/* No DBUG here */
 #endif
   FILESORT_INFO table_sort;
-  bzero(&table_sort, sizeof(FILESORT_INFO));
+  /* 
+    don't use table->sort in filesort as it is also used by 
+    QUICK_INDEX_MERGE_SELECT. work with a copy of it and put it back at the 
+    end when index_merge select has finished with it.
+  */
+  memcpy(&table_sort, &table->sort, sizeof(FILESORT_INFO));
+  table->sort.io_cache= NULL;
   
-  outfile= table->sort.io_cache;
+  outfile= table_sort.io_cache;
   my_b_clear(&tempfile);
   my_b_clear(&buffpek_pointers);
   buffpek=0;
@@ -261,7 +267,6 @@ ha_rows filesort(THD *thd, TABLE *table, SORT_FIELD *sortorder, uint s_length,
   DBUG_POP();			/* Ok to DBUG */
 #endif
   memcpy(&table->sort, &table_sort, sizeof(FILESORT_INFO));
-  table->sort.io_cache= outfile;
   DBUG_PRINT("exit",("records: %ld",records));
   DBUG_RETURN(error ? HA_POS_ERROR : records);
 } /* filesort */
@@ -445,7 +450,13 @@ static ha_rows find_all_keys(SORTPARAM *param, SQL_SELECT *select,
       file->unlock_row();
   }
   if (quick_select)
+  {
+    /*
+      index_merge quick select uses table->sort when retrieving rows, so free 
+      resoures it has allocated.
+    */
     end_read_record(&read_record_info);
+  }
   else
   {
     (void) file->extra(HA_EXTRA_NO_CACHE);	/* End cacheing of records */

sql/ha_berkeley.h

@@ -167,6 +167,7 @@ class ha_berkeley: public handler
   longlong get_auto_increment();
   void print_error(int error, myf errflag);
   uint8 table_cache_type() { return HA_CACHE_TBL_TRANSACT; }
+  bool primary_key_is_clustered_covering() { return true; }
 };
 
 extern bool berkeley_skip, berkeley_shared_data;

sql/ha_innodb.cc

@@ -2001,10 +2001,12 @@ build_template(
 		update field->query_id so that the formula
 		thd->query_id == field->query_id did not work. */
 
-		if (templ_type == ROW_MYSQL_REC_FIELDS
-		    && !(fetch_all_in_key
-			 && dict_index_contains_col_or_prefix(index, i))
-		    && thd->query_id != field->query_id) {
+                ibool index_contains_field = dict_index_contains_col_or_prefix(index, i);
+
+		if (templ_type == ROW_MYSQL_REC_FIELDS && 
+                    ((prebuilt->read_just_key && !index_contains_field) ||
+		    (!(fetch_all_in_key && index_contains_field)
+		     && thd->query_id != field->query_id))) {
 
 			/* This field is not needed in the query, skip it */
 

sql/ha_innodb.h

@@ -187,6 +187,7 @@ class ha_innobase: public handler
 	void init_table_handle_for_HANDLER(); 
 	longlong get_auto_increment();
         uint8 table_cache_type() { return HA_CACHE_TBL_ASKTRANSACT; }
+        bool primary_key_is_clustered_covering() { return true; }
 };
 
 extern bool innodb_skip;

sql/handler.h

@@ -368,6 +368,13 @@ class handler :public Sql_alloc
   */
   static bool caching_allowed(THD* thd, char* table_key,
 			      uint key_length, uint8 cahe_type);
+
+  /*
+   RETURN
+     true  primary key (if there is one) is clustered key covering all fields
+     false otherwise
+  */
+  virtual bool primary_key_is_clustered_covering() { return false; }
 };
 
 	/* Some extern variables used with handlers */

sql/opt_range.h

@@ -68,7 +68,7 @@ class QUICK_RANGE :public Sql_alloc {
 
 /*
   Quick select interface. 
-  This class is parent for all QUICK_*_SELECT and FT_SELECT classes.
+  This class is a parent for all QUICK_*_SELECT and FT_SELECT classes.
 */
 
 class QUICK_SELECT_I
@@ -128,19 +128,29 @@ class QUICK_RANGE_SELECT : public QUICK_SELECT_I
                                               SEL_ARG *key_tree,
                                               MEM_ROOT *alloc);
   friend class QUICK_SELECT_DESC;
+  friend class QUICK_INDEX_MERGE_SELECT;
+
+  DYNAMIC_ARRAY ranges;     /* ordered array of range ptrs */
+  QUICK_RANGE **cur_range;  /* current element in ranges  */
 
-  List<QUICK_RANGE> ranges;
-  List_iterator<QUICK_RANGE> it;
   QUICK_RANGE *range;
   MEM_ROOT alloc;
   KEY_PART *key_parts;  
   int cmp_next(QUICK_RANGE *range);
+  int cmp_prev(QUICK_RANGE *range);
+  bool row_in_ranges();
 public:
   QUICK_RANGE_SELECT(THD *thd, TABLE *table,uint index_arg,bool no_alloc=0,
                      MEM_ROOT *parent_alloc=NULL);
   ~QUICK_RANGE_SELECT();
   
-  int reset(void) { next=0; it.rewind(); return 0; }
+  int reset(void)
+  {
+    next=0; 
+    range= NULL; 
+    cur_range= NULL;
+    return 0;
+  }
   int init();
   int get_next();
   bool reverse_sorted() { return 0; }
@@ -148,9 +158,60 @@ class QUICK_RANGE_SELECT : public QUICK_SELECT_I
   int get_type() { return QS_TYPE_RANGE; }
 };
 
+
 /*
-  Index merge quick select. 
-  It is implemented as a container for several QUICK_RANGE_SELECTs.
+QUICK_INDEX_MERGE_SELECT - index_merge acces method quick select.
+
+  QUICK_INDEX_MERGE_SELECT uses 
+   * QUICK_RANGE_SELECTs to get rows
+   * Unique class to remove duplicate rows
+
+INDEX MERGE OPTIMIZER
+  Current implementation doesn't detect all cases where index_merge could be 
+  used, in particular:
+   * index_merge will never be used if range scan is possible (even if range 
+     scan is more expensive)
+
+   * index_merge+'using index' is not supported (this the consequence of the 
+     above restriction)
+   
+   * If WHERE part contains complex nested AND and OR conditions, some ways to
+     retrieve rows using index_merge will not be considered. The choice of 
+     read plan may depend on the order of conjuncts/disjuncts in WHERE part of
+     the query, see comments near SEL_IMERGE::or_sel_tree_with_checks and 
+     imerge_list_or_list function for details.
+
+   * there is no "index_merge_ref" method (but index_merge on non-first table 
+     in join is possible with 'range checked for each record').
+
+   See comments around SEL_IMERGE class and test_quick_select for more details.
+
+ROW RETRIEVAL ALGORITHM
+
+  index_merge uses Unique class for duplicates removal.  Index merge takes 
+  advantage of clustered covering primary key (CCPK) if the table has one.
+  The algorithm is as follows:
+
+  prepare() //implemented in QUICK_INDEX_MERGE_SELECT::prepare_unique
+  {
+    activate 'index only';
+    while(retrieve next row for non-CCPK scan)
+    {
+      if (there is a CCPK scan and row will be retrieved by it)
+        skip this row;
+      else
+        put rowid into Unique;
+    }
+    deactivate 'index only';
+  }
+
+  fetch() //implemented as sequence of QUICK_INDEX_MERGE_SELECT::get_next calls
+  {
+    retrieve all rows from row pointers stored in Unique;
+    free Unique;
+    retrieve all rows for CCPK scan;
+  }
+
 */
 
 class QUICK_INDEX_MERGE_SELECT : public QUICK_SELECT_I 
@@ -175,15 +236,24 @@ class QUICK_INDEX_MERGE_SELECT : public QUICK_SELECT_I
   List_iterator_fast<QUICK_RANGE_SELECT> cur_quick_it;
   QUICK_RANGE_SELECT* cur_quick_select;
   
-  /* last element in quick_selects list. */
+  /* last element in quick_selects list */
   QUICK_RANGE_SELECT* last_quick_select;
 
+  /* quick select that uses Covering Clustered Primary Key (NULL if none) */
+  QUICK_RANGE_SELECT* pk_quick_select;
+  
+  /* true if this select is currently doing a CCPK scan */
+  bool  doing_pk_scan;
+  
   Unique  *unique;
   MEM_ROOT alloc;
 
   THD *thd;
   int prepare_unique();
   bool reset_called;
+  
+  /* used to get rows collected in Unique */
+  READ_RECORD read_record;
 };
 
 class QUICK_SELECT_DESC: public QUICK_RANGE_SELECT
@@ -194,7 +264,6 @@ class QUICK_SELECT_DESC: public QUICK_RANGE_SELECT
   bool reverse_sorted() { return 1; }
   int get_type() { return QS_TYPE_RANGE_DESC; }
 private:
-  int cmp_prev(QUICK_RANGE *range);
   bool range_reads_after_key(QUICK_RANGE *range);
 #ifdef NOT_USED
   bool test_if_null_range(QUICK_RANGE *range, uint used_key_parts);

sql/records.cc

@@ -97,8 +97,8 @@ void init_read_record(READ_RECORD *info,THD *thd, TABLE *table,
       }
     }
   }
-  else if (select && select->quick && 
-           (select->quick->get_type() != QUICK_SELECT_I::QS_TYPE_INDEX_MERGE))
+  else if (select && select->quick)
+           //&& (select->quick->get_type() != QUICK_SELECT_I::QS_TYPE_INDEX_MERGE))
   {
     DBUG_PRINT("info",("using rr_quick"));
     info->read_record=rr_quick;