Ported WL#3220 to mysql-next-mr.

mysql-test/mysql-test-run.pl

@@ -5085,7 +5085,6 @@ sub valgrind_arguments {
   else
   {
     mtr_add_arg($args, "--tool=memcheck"); # From >= 2.1.2 needs this option
-    mtr_add_arg($args, "--alignment=8");
     mtr_add_arg($args, "--leak-check=yes");
     mtr_add_arg($args, "--num-callers=16");
     mtr_add_arg($args, "--suppressions=%s/valgrind.supp", $glob_mysql_test_dir)

mysql-test/r/bench_count_distinct.result

@@ -5,7 +5,7 @@ count(distinct n)
 100
 explain extended select count(distinct n) from t1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	SIMPLE	t1	index	NULL	n	4	NULL	200	100.00	Using index
+1	SIMPLE	t1	range	NULL	n	4	NULL	10	100.00	Using index for group-by
 Warnings:
 Note	1003	select count(distinct `test`.`t1`.`n`) AS `count(distinct n)` from `test`.`t1`
 drop table t1;

mysql-test/t/group_min_max.test

@@ -570,13 +570,13 @@ explain select count(distinct a1,a2,b) from t1 where (a2 >= 'b') and (b = 'a');
 explain select count(distinct a1,a2,b,c) from t1 where (a2 >= 'b') and (b = 'a') and (c = 'i121');
 explain extended select count(distinct a1,a2,b) from t1 where (a1 > 'a') and (a2 > 'a') and (b = 'c');
 explain select count(distinct b) from t1 where (a2 >= 'b') and (b = 'a');
-explain extended select ord(a1) + count(distinct a1,a2,b) from t1 where (a1 > 'a') and (a2 > 'a');
+explain extended select 98 + count(distinct a1,a2,b) from t1 where (a1 > 'a') and (a2 > 'a');
 
 select count(distinct a1,a2,b) from t1 where (a2 >= 'b') and (b = 'a');
 select count(distinct a1,a2,b,c) from t1 where (a2 >= 'b') and (b = 'a') and (c = 'i121');
 select count(distinct a1,a2,b) from t1 where (a1 > 'a') and (a2 > 'a') and (b = 'c');
 select count(distinct b) from t1 where (a2 >= 'b') and (b = 'a');
-select ord(a1) + count(distinct a1,a2,b) from t1 where (a1 > 'a') and (a2 > 'a');
+select 98 + count(distinct a1,a2,b) from t1 where (a1 > 'a') and (a2 > 'a');
 
 #
 # Queries with expressions in the select clause
@@ -1033,3 +1033,124 @@ SELECT a, MAX(b) FROM t WHERE b GROUP BY a;
 DROP TABLE t;
 
 --echo End of 5.1 tests
+
+
+--echo #
+--echo # WL#3220 (Loose index scan for COUNT DISTINCT)
+--echo #
+
+CREATE TABLE t1 (a INT, b INT, c INT, KEY (a,b));
+INSERT INTO t1 VALUES (1,1,1), (1,2,1), (1,3,1), (1,4,1);
+INSERT INTO t1 SELECT a, b + 4, 1 FROM t1;
+INSERT INTO t1 SELECT a + 1, b, 1 FROM t1;
+CREATE TABLE t2 (a INT, b INT, c INT, d INT, e INT, f INT, KEY (a,b,c));
+INSERT INTO t2 VALUES (1,1,1,1,1,1), (1,2,1,1,1,1), (1,3,1,1,1,1), 
+       (1,4,1,1,1,1);
+INSERT INTO t2 SELECT a, b + 4, c,d,e,f FROM t2;
+INSERT INTO t2 SELECT a + 1, b, c,d,e,f FROM t2;
+
+EXPLAIN SELECT COUNT(DISTINCT a) FROM t1;
+SELECT COUNT(DISTINCT a) FROM t1;
+
+EXPLAIN SELECT COUNT(DISTINCT a,b) FROM t1;
+SELECT COUNT(DISTINCT a,b) FROM t1;
+
+EXPLAIN SELECT COUNT(DISTINCT b,a) FROM t1;
+SELECT COUNT(DISTINCT b,a) FROM t1;
+
+EXPLAIN SELECT COUNT(DISTINCT b) FROM t1;
+SELECT COUNT(DISTINCT b) FROM t1;
+
+EXPLAIN SELECT COUNT(DISTINCT a) FROM t1 GROUP BY a;
+SELECT COUNT(DISTINCT a) FROM t1 GROUP BY a;
+
+EXPLAIN SELECT COUNT(DISTINCT b) FROM t1 GROUP BY a;
+SELECT COUNT(DISTINCT b) FROM t1 GROUP BY a;
+
+EXPLAIN SELECT COUNT(DISTINCT a) FROM t1 GROUP BY b;
+SELECT COUNT(DISTINCT a) FROM t1 GROUP BY b;
+
+EXPLAIN SELECT DISTINCT COUNT(DISTINCT a) FROM t1;
+SELECT DISTINCT COUNT(DISTINCT a) FROM t1;
+
+EXPLAIN SELECT COUNT(DISTINCT a, b + 0) FROM t1;
+SELECT COUNT(DISTINCT a, b + 0) FROM t1;
+
+EXPLAIN SELECT COUNT(DISTINCT a) FROM t1 HAVING COUNT(DISTINCT b) < 10;
+SELECT COUNT(DISTINCT a) FROM t1 HAVING COUNT(DISTINCT b) < 10;
+
+EXPLAIN SELECT COUNT(DISTINCT a) FROM t1 HAVING COUNT(DISTINCT c) < 10;
+SELECT COUNT(DISTINCT a) FROM t1 HAVING COUNT(DISTINCT c) < 10;
+
+EXPLAIN SELECT 1 FROM t1 HAVING COUNT(DISTINCT a) < 10;
+SELECT 1 FROM t1 HAVING COUNT(DISTINCT a) < 10;
+
+EXPLAIN SELECT 1 FROM t1 GROUP BY a HAVING COUNT(DISTINCT b) > 1;
+SELECT 1 FROM t1 GROUP BY a HAVING COUNT(DISTINCT b) > 1;
+
+EXPLAIN SELECT COUNT(DISTINCT t1_1.a) FROM t1 t1_1, t1 t1_2 GROUP BY t1_1.a;
+SELECT COUNT(DISTINCT t1_1.a) FROM t1 t1_1, t1 t1_2 GROUP BY t1_1.a;
+
+EXPLAIN SELECT COUNT(DISTINCT a), 12 FROM t1;
+SELECT COUNT(DISTINCT a), 12 FROM t1;
+
+EXPLAIN SELECT COUNT(DISTINCT a, b, c) FROM t2;
+SELECT COUNT(DISTINCT a, b, c) FROM t2;
+
+EXPLAIN SELECT COUNT(DISTINCT a), SUM(DISTINCT a), AVG(DISTINCT a) FROM t2;
+SELECT COUNT(DISTINCT a), SUM(DISTINCT a), AVG(DISTINCT a) FROM t2;
+
+EXPLAIN SELECT COUNT(DISTINCT a), SUM(DISTINCT a), AVG(DISTINCT f) FROM t2;
+SELECT COUNT(DISTINCT a), SUM(DISTINCT a), AVG(DISTINCT f) FROM t2;
+
+EXPLAIN SELECT COUNT(DISTINCT a, b), COUNT(DISTINCT b, a) FROM t2;
+SELECT COUNT(DISTINCT a, b), COUNT(DISTINCT b, a) FROM t2;
+
+EXPLAIN SELECT COUNT(DISTINCT a, b), COUNT(DISTINCT b, f) FROM t2;
+SELECT COUNT(DISTINCT a, b), COUNT(DISTINCT b, f) FROM t2;
+
+EXPLAIN SELECT COUNT(DISTINCT a, b), COUNT(DISTINCT b, d) FROM t2;
+SELECT COUNT(DISTINCT a, b), COUNT(DISTINCT b, d) FROM t2;
+
+EXPLAIN SELECT a, c, COUNT(DISTINCT c, a, b) FROM t2 GROUP BY a, b, c;
+SELECT a, c, COUNT(DISTINCT c, a, b) FROM t2 GROUP BY a, b, c;
+
+EXPLAIN SELECT COUNT(DISTINCT c, a, b) FROM t2
+  WHERE a > 5 AND b BETWEEN 10 AND 20 GROUP BY a, b, c;
+SELECT COUNT(DISTINCT c, a, b) FROM t2
+  WHERE a > 5 AND b BETWEEN 10 AND 20 GROUP BY a, b, c;
+
+EXPLAIN SELECT COUNT(DISTINCT b), SUM(DISTINCT b) FROM t2 WHERE a = 5
+  GROUP BY b;
+SELECT COUNT(DISTINCT b), SUM(DISTINCT b) FROM t2 WHERE a = 5
+  GROUP BY b;
+
+EXPLAIN SELECT a, COUNT(DISTINCT b), SUM(DISTINCT b) FROM t2 GROUP BY a;
+SELECT a, COUNT(DISTINCT b), SUM(DISTINCT b) FROM t2 GROUP BY a;
+
+EXPLAIN SELECT COUNT(DISTINCT b), SUM(DISTINCT b) FROM t2 GROUP BY a;
+SELECT COUNT(DISTINCT b), SUM(DISTINCT b) FROM t2 GROUP BY a;
+
+EXPLAIN SELECT COUNT(DISTINCT a, b) FROM t2 WHERE c = 13 AND d = 42;
+SELECT COUNT(DISTINCT a, b) FROM t2 WHERE c = 13 AND d = 42;
+
+EXPLAIN SELECT a, COUNT(DISTINCT a), SUM(DISTINCT a) FROM t2
+  WHERE b = 13 AND c = 42 GROUP BY a;
+SELECT a, COUNT(DISTINCT a), SUM(DISTINCT a) FROM t2
+  WHERE b = 13 AND c = 42 GROUP BY a;
+
+EXPLAIN SELECT COUNT(DISTINCT a, b), SUM(DISTINCT a) FROM t2 WHERE b = 42;
+SELECT COUNT(DISTINCT a, b), SUM(DISTINCT a) FROM t2 WHERE b = 42;
+
+EXPLAIN SELECT SUM(DISTINCT a), MAX(b) FROM t2 GROUP BY a;
+SELECT SUM(DISTINCT a), MAX(b) FROM t2 GROUP BY a;
+
+EXPLAIN SELECT 42 * (a + c + COUNT(DISTINCT c, a, b)) FROM t2 GROUP BY a, b, c;
+SELECT 42 * (a + c + COUNT(DISTINCT c, a, b)) FROM t2 GROUP BY a, b, c;
+
+EXPLAIN SELECT (SUM(DISTINCT a) + MAX(b)) FROM t2 GROUP BY a;
+SELECT (SUM(DISTINCT a) + MAX(b)) FROM t2 GROUP BY a;
+
+DROP TABLE t1,t2;
+
+--echo # end of WL#3220 tests

sql/field.h

@@ -1935,8 +1935,11 @@ public:
   my_decimal *val_decimal(my_decimal *);
   int cmp(const uchar *a, const uchar *b)
   {
-    DBUG_ASSERT(ptr == a);
+    DBUG_ASSERT(ptr == a || ptr == b);
+    if (ptr == a)
       return Field_bit::key_cmp(b, bytes_in_rec+test(bit_len));
+    else
+      return Field_bit::key_cmp(a, bytes_in_rec+test(bit_len)) * -1;
   }
   int cmp_binary_offset(uint row_offset)
   { return cmp_offset(row_offset); }

sql/opt_range.h

@@ -616,6 +616,7 @@ private:
   uchar *last_prefix;     /* Prefix of the last group for detecting EOF. */
   bool have_min;         /* Specify whether we are computing */
   bool have_max;         /*   a MIN, a MAX, or both.         */
+  bool have_agg_distinct;/*   aggregate_function(DISTINCT ...).  */
   bool seen_first_key;   /* Denotes whether the first key was retrieved.*/
   KEY_PART_INFO *min_max_arg_part; /* The keypart of the only argument field */
                                    /* of all MIN/MAX functions.              */
@@ -629,6 +630,11 @@ private:
   List<Item_sum> *max_functions;
   List_iterator<Item_sum> *min_functions_it;
   List_iterator<Item_sum> *max_functions_it;
+  /* 
+    Use index scan to get the next different key instead of jumping into it 
+    through index read 
+  */
+  bool is_index_scan; 
 public:
   /*
     The following two members are public to allow easy access from
@@ -646,12 +652,13 @@ private:
   void update_max_result();
 public:
   QUICK_GROUP_MIN_MAX_SELECT(TABLE *table, JOIN *join, bool have_min,
-                             bool have_max, KEY_PART_INFO *min_max_arg_part,
+                             bool have_max, bool have_agg_distinct,
+                             KEY_PART_INFO *min_max_arg_part,
                              uint group_prefix_len, uint group_key_parts,
                              uint used_key_parts, KEY *index_info, uint
                              use_index, double read_cost, ha_rows records, uint
                              key_infix_len, uchar *key_infix, MEM_ROOT
-                             *parent_alloc);
+                             *parent_alloc, bool is_index_scan);
   ~QUICK_GROUP_MIN_MAX_SELECT();
   bool add_range(SEL_ARG *sel_range);
   void update_key_stat();
@@ -667,6 +674,12 @@ public:
 #ifndef DBUG_OFF
   void dbug_dump(int indent, bool verbose);
 #endif
+  bool is_agg_distinct() { return have_agg_distinct; }
+  virtual void append_loose_scan_type(String *str) 
+  {
+    if (is_index_scan)
+      str->append(STRING_WITH_LEN(" (scanning)"));
+  }
 };
 
 

sql/opt_sum.cc

@@ -355,10 +355,13 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds)
           const_result= 0;
           break;
         }
+        item_sum->set_aggregator (item_sum->with_distinct ? 
+                                  Aggregator::DISTINCT_AGGREGATOR :
+                                  Aggregator::SIMPLE_AGGREGATOR);
         if (!count)
         {
           /* If count == 0, then we know that is_exact_count == TRUE. */
-          ((Item_sum_min*) item_sum)->clear(); /* Set to NULL. */
+          ((Item_sum_min*) item_sum)->aggregator_clear(); /* Set to NULL. */
         }
         else
           ((Item_sum_min*) item_sum)->reset(); /* Set to the constant value. */
@@ -443,10 +446,13 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds)
           const_result= 0;
           break;
         }
+        item_sum->set_aggregator (item_sum->with_distinct ? 
+                                  Aggregator::DISTINCT_AGGREGATOR :
+                                  Aggregator::SIMPLE_AGGREGATOR);
         if (!count)
         {
           /* If count != 1, then we know that is_exact_count == TRUE. */
-          ((Item_sum_max*) item_sum)->clear(); /* Set to NULL. */
+          ((Item_sum_max*) item_sum)->aggregator_clear(); /* Set to NULL. */
         }
         else
           ((Item_sum_max*) item_sum)->reset(); /* Set to the constant value. */

sql/sql_class.h

@@ -54,6 +54,7 @@
 class Reprepare_observer
 {
 public:
+  Reprepare_observer() {}
   /**
     Check if a change of metadata is OK. In future
     the signature of this method may be extended to accept the old

sql/sql_select.cc

@@ -222,6 +222,7 @@ static void update_tmptable_sum_func(Item_sum **func,TABLE *tmp_table);
 static void copy_sum_funcs(Item_sum **func_ptr, Item_sum **end);
 static bool add_ref_to_table_cond(THD *thd, JOIN_TAB *join_tab);
 static bool setup_sum_funcs(THD *thd, Item_sum **func_ptr);
+static bool prepare_sum_aggregators(Item_sum **func_ptr, bool need_distinct);
 static bool init_sum_functions(Item_sum **func, Item_sum **end);
 static bool update_sum_func(Item_sum **func);
 static void select_describe(JOIN *join, bool need_tmp_table,bool need_order,
@@ -1232,7 +1233,11 @@ JOIN::optimize()
 
   if (test_if_subpart(group_list, order) ||
       (!group_list && tmp_table_param.sum_func_count))
+  {
     order=0;
+    if (is_indexed_agg_distinct(this, NULL))
+      sort_and_group= 0;
+  }
 
   // Can't use sort on head table if using row cache
   if (full_join)
@@ -1410,8 +1415,16 @@ JOIN::optimize()
     single table queries, thus it is sufficient to test only the first
     join_tab element of the plan for its access method.
   */
+  bool need_distinct= TRUE;
   if (join_tab->is_using_loose_index_scan())
+  {
     tmp_table_param.precomputed_group_by= TRUE;
+    if (join_tab->is_using_agg_loose_index_scan())
+    {
+      need_distinct= FALSE;
+      tmp_table_param.precomputed_group_by= FALSE;
+    }
+  }
 
   /* Create a tmp table if distinct or if the sort is too complicated */
   if (need_tmp)
@@ -1472,6 +1485,7 @@ JOIN::optimize()
 			    HA_POS_ERROR, HA_POS_ERROR, FALSE) ||
 	  alloc_group_fields(this, group_list) ||
           make_sum_func_list(all_fields, fields_list, 1) ||
+          prepare_sum_aggregators(sum_funcs, need_distinct) ||
           setup_sum_funcs(thd, sum_funcs))
       {
         DBUG_RETURN(1);
@@ -1481,6 +1495,7 @@ JOIN::optimize()
     else
     {
       if (make_sum_func_list(all_fields, fields_list, 0) ||
+          prepare_sum_aggregators(sum_funcs, need_distinct) ||
           setup_sum_funcs(thd, sum_funcs))
       {
         DBUG_RETURN(1);
@@ -1953,7 +1968,9 @@ JOIN::exec()
 	}
       }
       if (curr_join->make_sum_func_list(*curr_all_fields, *curr_fields_list,
-					1, TRUE))
+					1, TRUE) ||
+        prepare_sum_aggregators(curr_join->sum_funcs,
+          !curr_join->join_tab->is_using_agg_loose_index_scan()))
         DBUG_VOID_RETURN;
       curr_join->group_list= 0;
       if (!curr_join->sort_and_group &&
@@ -2056,6 +2073,8 @@ JOIN::exec()
 
     if (curr_join->make_sum_func_list(*curr_all_fields, *curr_fields_list,
 				      1, TRUE) || 
+        prepare_sum_aggregators (curr_join->sum_funcs, !curr_join->join_tab ||
+                                !curr_join->join_tab->is_using_agg_loose_index_scan()) ||
         setup_sum_funcs(curr_join->thd, curr_join->sum_funcs) ||
         thd->is_fatal_error)
       DBUG_VOID_RETURN;
@@ -3937,6 +3956,82 @@ static void optimize_keyuse(JOIN *join, DYNAMIC_ARRAY *keyuse_array)
 }
 
 
+/**
+  Check for the presence of AGGFN(DISTINCT a) queries that may be subject
+  to loose index scan.
+
+
+  Check if the query is a subject to AGGFN(DISTINCT) using loose index scan 
+  (QUICK_GROUP_MIN_MAX_SELECT).
+  Optionally (if out_args is supplied) will push the arguments of 
+  AGGFN(DISTINCT) to the list
+
+  @param      join       the join to check
+  @param[out] out_args   list of aggregate function arguments
+  @return                does the query qualify for indexed AGGFN(DISTINCT)
+    @retval   true       it does
+    @retval   false      AGGFN(DISTINCT) must apply distinct in it.
+*/
+
+bool
+is_indexed_agg_distinct(JOIN *join, List<Item_field> *out_args)
+{
+  Item_sum **sum_item_ptr;
+  bool result= false;
+
+  if (join->tables != 1 ||                    /* reference more than 1 table */
+      join->select_distinct ||                /* or a DISTINCT */
+      join->select_lex->olap == ROLLUP_TYPE)  /* Check (B3) for ROLLUP */
+    return false;
+
+  if (join->make_sum_func_list(join->all_fields, join->fields_list, 1))
+    return false;
+
+  for (sum_item_ptr= join->sum_funcs; *sum_item_ptr; sum_item_ptr++)
+  {
+    Item_sum *sum_item= *sum_item_ptr;
+    Item *expr;
+    /* aggregate is not AGGFN(DISTINCT) or more than 1 argument to it */
+    switch (sum_item->sum_func())
+    {
+      case Item_sum::MIN_FUNC:
+      case Item_sum::MAX_FUNC:
+        continue;
+      case Item_sum::COUNT_DISTINCT_FUNC: 
+        break;
+      case Item_sum::AVG_DISTINCT_FUNC:
+      case Item_sum::SUM_DISTINCT_FUNC:
+        if (sum_item->get_arg_count() == 1) 
+          break;
+        /* fall through */
+      default: return false;
+    }
+    /*
+      We arrive here for every COUNT(DISTINCT),AVG(DISTINCT) or SUM(DISTINCT).
+      Collect the arguments of the aggregate functions to a list.
+      We don't worry about duplicates as these will be sorted out later in 
+      get_best_group_min_max 
+    */
+    for (uint i= 0; i < sum_item->get_arg_count(); i++)
+    {
+      expr= sum_item->get_arg(i);
+      /* The AGGFN(DISTINCT) arg is not an attribute? */
+      if (expr->real_item()->type() != Item::FIELD_ITEM)
+        return false;
+
+      /* 
+        If we came to this point the AGGFN(DISTINCT) loose index scan
+        optimization is applicable 
+      */
+      if (out_args)
+        out_args->push_back((Item_field *) expr);
+      result= true;
+    }
+  }
+  return result;
+}
+
+
 /**
   Discover the indexes that can be used for GROUP BY or DISTINCT queries.
 
@@ -3979,6 +4074,10 @@ add_group_and_distinct_keys(JOIN *join, JOIN_TAB *join_tab)
       item->walk(&Item::collect_item_field_processor, 0,
                  (uchar*) &indexed_fields);
   }
+  else if (is_indexed_agg_distinct(join, &indexed_fields))
+  {
+    join->sort_and_group= 1;
+  }
   else
     return;
 
@@ -10377,6 +10476,7 @@ TABLE *create_virtual_tmp_table(THD *thd, List<Create_field> &field_list)
   bzero(share, sizeof(*share));
   table->field= field;
   table->s= share;
+  table->temp_pool_slot= MY_BIT_NONE;
   share->blob_field= blob_field;
   share->fields= field_count;
   share->blob_ptr_size= portable_sizeof_char_ptr;
@@ -14532,7 +14632,7 @@ setup_new_fields(THD *thd, List<Item> &fields,
   optimize away 'order by'.
 */
 
-static ORDER *
+ORDER *
 create_distinct_group(THD *thd, Item **ref_pointer_array,
                       ORDER *order_list, List<Item> &fields,
                       List<Item> &all_fields,
@@ -15334,7 +15434,22 @@ static bool setup_sum_funcs(THD *thd, Item_sum **func_ptr)
   DBUG_ENTER("setup_sum_funcs");
   while ((func= *(func_ptr++)))
   {
-    if (func->setup(thd))
+    if (func->aggregator_setup(thd))
+      DBUG_RETURN(TRUE);
+  }
+  DBUG_RETURN(FALSE);
+}
+
+
+static bool prepare_sum_aggregators(Item_sum **func_ptr, bool need_distinct)
+{
+  Item_sum *func;
+  DBUG_ENTER("setup_sum_funcs");
+  while ((func= *(func_ptr++)))
+  {
+    if (func->set_aggregator(need_distinct && func->with_distinct ?
+                             Aggregator::DISTINCT_AGGREGATOR :
+                             Aggregator::SIMPLE_AGGREGATOR))
       DBUG_RETURN(TRUE);
   }
   DBUG_RETURN(FALSE);
@@ -15384,7 +15499,7 @@ init_sum_functions(Item_sum **func_ptr, Item_sum **end_ptr)
   /* If rollup, calculate the upper sum levels */
   for ( ; *func_ptr ; func_ptr++)
   {
-    if ((*func_ptr)->add())
+    if ((*func_ptr)->aggregator_add())
       return 1;
   }
   return 0;
@@ -15396,7 +15511,7 @@ update_sum_func(Item_sum **func_ptr)
 {
   Item_sum *func;
   for (; (func= (Item_sum*) *func_ptr) ; func_ptr++)
-    if (func->add())
+    if (func->aggregator_add())
       return 1;
   return 0;
 }
@@ -16313,7 +16428,12 @@ static void select_describe(JOIN *join, bool need_tmp_table, bool need_order,
 	if (key_read)
         {
           if (quick_type == QUICK_SELECT_I::QS_TYPE_GROUP_MIN_MAX)
+          {
+            QUICK_GROUP_MIN_MAX_SELECT *qgs= 
+              (QUICK_GROUP_MIN_MAX_SELECT *) tab->select->quick;
             extra.append(STRING_WITH_LEN("; Using index for group-by"));
+            qgs->append_loose_scan_type(&extra);
+          }
           else
             extra.append(STRING_WITH_LEN("; Using index"));
         }

sql/sql_select.h

@@ -218,6 +218,11 @@ typedef struct st_join_table {
             (select->quick->get_type() ==
              QUICK_SELECT_I::QS_TYPE_GROUP_MIN_MAX));
   }
+  bool is_using_agg_loose_index_scan ()
+  {
+    return (is_using_loose_index_scan() &&
+            ((QUICK_GROUP_MIN_MAX_SELECT *)select->quick)->is_agg_distinct());
+  }
 } JOIN_TAB;
 
 enum_nested_loop_state sub_select_cache(JOIN *join, JOIN_TAB *join_tab, bool
@@ -564,6 +569,8 @@ Field* create_tmp_field_from_field(THD *thd, Field* org_field,
                                    const char *name, TABLE *table,
                                    Item_field *item, uint convert_blob_length);
                                                                       
+bool is_indexed_agg_distinct(JOIN *join, List<Item_field> *out_args);
+
 /* functions from opt_sum.cc */
 bool simple_pred(Item_func *func_item, Item **args, bool *inv_order);
 int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds);

sql/sql_yacc.yy

@@ -8128,7 +8128,7 @@ sum_expr:
           }
         | AVG_SYM '(' DISTINCT in_sum_expr ')'
           {
-            $$= new (YYTHD->mem_root) Item_sum_avg_distinct($4);
+            $$= new (YYTHD->mem_root) Item_sum_avg($4, TRUE);
             if ($$ == NULL)
               MYSQL_YYABORT;
           }
@@ -8171,7 +8171,7 @@ sum_expr:
           { Select->in_sum_expr--; }
           ')'
           {
-            $$= new (YYTHD->mem_root) Item_sum_count_distinct(* $5);
+            $$= new (YYTHD->mem_root) Item_sum_count(* $5);
             if ($$ == NULL)
               MYSQL_YYABORT;
           }
@@ -8236,7 +8236,7 @@ sum_expr:
           }
         | SUM_SYM '(' DISTINCT in_sum_expr ')'
           {
-            $$= new (YYTHD->mem_root) Item_sum_sum_distinct($4);
+            $$= new (YYTHD->mem_root) Item_sum_sum($4, TRUE);
             if ($$ == NULL)
               MYSQL_YYABORT;
           }