merged the fix for bug 41610 to 5.1-bugteam

mysql-test/r/group_min_max.result

@@ -2448,3 +2448,18 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 Warnings:
 Note	1003	select sql_buffer_result `test`.`t1`.`a` AS `a`,(max(`test`.`t1`.`b`) + 1) AS `max(b)+1` from `test`.`t1` where (`test`.`t1`.`a` = 0) group by `test`.`t1`.`a`
 drop table t1;
+CREATE TABLE t1 (a int, b int, c int, d int,
+KEY foo (c,d,a,b), KEY bar (c,a,b,d));
+INSERT INTO t1 VALUES (1, 1, 1, 1), (1, 1, 1, 2), (1, 1, 1, 3), (1, 1, 1, 4);
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT a,b,c+1,d FROM t1;
+EXPLAIN SELECT DISTINCT c FROM t1 WHERE d=4;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	NULL	foo	10	NULL	9	Using where; Using index for group-by
+SELECT DISTINCT c FROM t1 WHERE d=4;
+c
+1
+2
+DROP TABLE t1;
+End of 5.0 tests

mysql-test/t/group_min_max.test

@@ -961,3 +961,25 @@ insert into t1 (a,b) select a, max(b)+1 from t1 where a = 0 group by a;
 select * from t1;
 explain extended select sql_buffer_result a, max(b)+1 from t1 where a = 0 group by a;
 drop table t1;
+
+
+#
+# Bug #41610: key_infix_len can be overwritten causing some group by queries
+# to return no rows
+#
+
+CREATE TABLE t1 (a int, b int, c int, d int,
+  KEY foo (c,d,a,b), KEY bar (c,a,b,d));
+
+INSERT INTO t1 VALUES (1, 1, 1, 1), (1, 1, 1, 2), (1, 1, 1, 3), (1, 1, 1, 4);
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT a,b,c+1,d FROM t1;
+
+#Should be non-empty
+EXPLAIN SELECT DISTINCT c FROM t1 WHERE d=4;
+SELECT DISTINCT c FROM t1 WHERE d=4;
+
+DROP TABLE t1;
+
+--echo End of 5.0 tests

sql/opt_range.cc

@@ -9239,32 +9239,37 @@ get_best_group_min_max(PARAM *param, SEL_TREE *tree)
   */
   KEY *cur_index_info= table->key_info;
   KEY *cur_index_info_end= cur_index_info + table->s->keys;
-  KEY_PART_INFO *cur_part= NULL;
-  KEY_PART_INFO *end_part; /* Last part for loops. */
-  /* Last index part. */
-  KEY_PART_INFO *last_part= NULL;
-  KEY_PART_INFO *first_non_group_part= NULL;
-  KEY_PART_INFO *first_non_infix_part= NULL;
-  uint key_infix_parts= 0;
-  uint cur_group_key_parts= 0;
-  uint cur_group_prefix_len= 0;
   /* Cost-related variables for the best index so far. */
   double best_read_cost= DBL_MAX;
   ha_rows best_records= 0;
   SEL_ARG *best_index_tree= NULL;
   ha_rows best_quick_prefix_records= 0;
   uint best_param_idx= 0;
-  double cur_read_cost= DBL_MAX;
-  ha_rows cur_records;
+
+  const uint pk= param->table->s->primary_key;
   SEL_ARG *cur_index_tree= NULL;
   ha_rows cur_quick_prefix_records= 0;
   uint cur_param_idx=MAX_KEY;
-  key_map cur_used_key_parts;
-  uint pk= param->table->s->primary_key;
 
   for (uint cur_index= 0 ; cur_index_info != cur_index_info_end ;
        cur_index_info++, cur_index++)
   {
+    KEY_PART_INFO *cur_part;
+    KEY_PART_INFO *end_part; /* Last part for loops. */
+    /* Last index part. */
+    KEY_PART_INFO *last_part;
+    KEY_PART_INFO *first_non_group_part;
+    KEY_PART_INFO *first_non_infix_part;
+    uint key_infix_parts;
+    uint cur_group_key_parts= 0;
+    uint cur_group_prefix_len= 0;
+    double cur_read_cost;
+    ha_rows cur_records;
+    key_map used_key_parts_map;
+    uint cur_key_infix_len= 0;
+    uchar cur_key_infix[MAX_KEY_LENGTH];
+    uint cur_used_key_parts;
+    
     /* Check (B1) - if current index is covering. */
     if (!table->covering_keys.is_set(cur_index))
       goto next_index;
@@ -9334,7 +9339,7 @@ get_best_group_min_max(PARAM *param, SEL_TREE *tree)
     else if (join->select_distinct)
     {
       select_items_it.rewind();
-      cur_used_key_parts.clear_all();
+      used_key_parts_map.clear_all();
       uint max_key_part= 0;
       while ((item= select_items_it++))
       {
@@ -9345,13 +9350,13 @@ get_best_group_min_max(PARAM *param, SEL_TREE *tree)
           Check if this attribute was already present in the select list.
           If it was present, then its corresponding key part was alredy used.
         */
-        if (cur_used_key_parts.is_set(key_part_nr))
+        if (used_key_parts_map.is_set(key_part_nr))
           continue;
         if (key_part_nr < 1 || key_part_nr > join->fields_list.elements)
           goto next_index;
         cur_part= cur_index_info->key_part + key_part_nr - 1;
         cur_group_prefix_len+= cur_part->store_length;
-        cur_used_key_parts.set_bit(key_part_nr);
+        used_key_parts_map.set_bit(key_part_nr);
         ++cur_group_key_parts;
         max_key_part= max(max_key_part,key_part_nr);
       }
@@ -9363,7 +9368,7 @@ get_best_group_min_max(PARAM *param, SEL_TREE *tree)
       */
       ulonglong all_parts, cur_parts;
       all_parts= (1<<max_key_part) - 1;
-      cur_parts= cur_used_key_parts.to_ulonglong() >> 1;
+      cur_parts= used_key_parts_map.to_ulonglong() >> 1;
       if (all_parts != cur_parts)
         goto next_index;
     }
@@ -9413,7 +9418,8 @@ get_best_group_min_max(PARAM *param, SEL_TREE *tree)
                                                         &dummy);
         if (!get_constant_key_infix(cur_index_info, index_range_tree,
                                     first_non_group_part, min_max_arg_part,
-                                    last_part, thd, key_infix, &key_infix_len,
+                                    last_part, thd, cur_key_infix, 
+                                    &cur_key_infix_len,
                                     &first_non_infix_part))
           goto next_index;
       }
@@ -9467,9 +9473,9 @@ get_best_group_min_max(PARAM *param, SEL_TREE *tree)
     }
 
     /* If we got to this point, cur_index_info passes the test. */
-    key_infix_parts= key_infix_len ?
+    key_infix_parts= cur_key_infix_len ?
                      (first_non_infix_part - first_non_group_part) : 0;
-    used_key_parts= cur_group_key_parts + key_infix_parts;
+    cur_used_key_parts= cur_group_key_parts + key_infix_parts;
 
     /* Compute the cost of using this index. */
     if (tree)
@@ -9481,7 +9487,7 @@ get_best_group_min_max(PARAM *param, SEL_TREE *tree)
       cur_quick_prefix_records= check_quick_select(param, cur_param_idx,
                                                     cur_index_tree, TRUE);
     }
-    cost_group_min_max(table, cur_index_info, used_key_parts,
+    cost_group_min_max(table, cur_index_info, cur_used_key_parts,
                        cur_group_key_parts, tree, cur_index_tree,
                        cur_quick_prefix_records, have_min, have_max,
                        &cur_read_cost, &cur_records);
@@ -9492,7 +9498,6 @@ get_best_group_min_max(PARAM *param, SEL_TREE *tree)
     */
     if (cur_read_cost < best_read_cost - (DBL_EPSILON * cur_read_cost))
     {
-      DBUG_ASSERT(tree != 0 || cur_param_idx == MAX_KEY);
       index_info= cur_index_info;
       index= cur_index;
       best_read_cost= cur_read_cost;
@@ -9502,11 +9507,13 @@ get_best_group_min_max(PARAM *param, SEL_TREE *tree)
       best_param_idx= cur_param_idx;
       group_key_parts= cur_group_key_parts;
       group_prefix_len= cur_group_prefix_len;
+      key_infix_len= cur_key_infix_len;
+      if (key_infix_len)
+        memcpy (key_infix, cur_key_infix, sizeof (key_infix));
+      used_key_parts= cur_used_key_parts;
     }
 
-  next_index:
-    cur_group_key_parts= 0;
-    cur_group_prefix_len= 0;
+  next_index:;
   }
   if (!index_info) /* No usable index found. */
     DBUG_RETURN(NULL);