Bug #48131: crash group by with rollup, distinct, filesort,

with temporary tables

There were two problems the test case from this bug was
triggering:

1. JOIN::rollup_init() was supposed to wrap all constant Items
into another object for queries with the WITH ROLLUP modifier
to ensure they are never considered as constants and therefore
are written into temporary tables if the optimizer chooses to
employ them for DISTINCT/GROUP BY handling.

However, JOIN::rollup_init() was called before
make_join_statistics(), so Items corresponding to fields in
const tables could not be handled as intended, which was
causing all kinds of problems later in the query execution. In
particular, create_tmp_table() assumed all constant items
except "hidden" ones to be removed earlier by remove_const()
which led to improperly initialized Field objects for the
temporary table being created. This is what was causing crashes
and valgrind errors in storage engines.

2. Even when the above problem had been fixed, the query from
the test case produced incorrect results due to some
DISTINCT/GROUP BY optimizations being performed by the
optimizer that are inapplicable in the WITH ROLLUP case.

Fixed by disabling inapplicable DISTINCT/GROUP BY optimizations
when the WITH ROLLUP modifier is present, and splitting the
const-wrapping part of JOIN::rollup_init() into a separate
method which is now invoked after make_join_statistics() when
the const tables are already known.

mysql-test/r/olap.result

@@ -733,4 +733,24 @@ SELECT 1 FROM t1 GROUP BY (DATE(NULL)) WITH ROLLUP;
 1
 1
 DROP TABLE t1;
+#
+# Bug #48131: crash group by with rollup, distinct,
+#             filesort, with temporary tables
+#
+CREATE TABLE t1 (a INT NOT NULL PRIMARY KEY);
+INSERT INTO t1 VALUES (1), (2);
+CREATE TABLE t2 (b INT);
+INSERT INTO t2 VALUES (100);
+SELECT a, b FROM t1, t2 GROUP BY a, b WITH ROLLUP;
+a	b
+1	100
+1	NULL
+2	100
+2	NULL
+NULL	NULL
+SELECT DISTINCT b FROM t1, t2 GROUP BY a, b WITH ROLLUP;
+b
+100
+NULL
+DROP TABLE t1, t2;
 End of 5.0 tests

mysql-test/t/olap.test

@@ -375,4 +375,19 @@ INSERT INTO t1 VALUES(0);
 SELECT 1 FROM t1 GROUP BY (DATE(NULL)) WITH ROLLUP;
 DROP TABLE t1;
 
+--echo #
+--echo # Bug #48131: crash group by with rollup, distinct,
+--echo #             filesort, with temporary tables
+--echo #
+
+CREATE TABLE t1 (a INT NOT NULL PRIMARY KEY);
+INSERT INTO t1 VALUES (1), (2);
+CREATE TABLE t2 (b INT);
+INSERT INTO t2 VALUES (100);
+
+SELECT a, b FROM t1, t2 GROUP BY a, b WITH ROLLUP;
+SELECT DISTINCT b FROM t1, t2 GROUP BY a, b WITH ROLLUP;
+
+DROP TABLE t1, t2;
+
 --echo End of 5.0 tests

sql/sql_select.cc

@@ -916,6 +916,12 @@ JOIN::optimize()
     DBUG_RETURN(1);
   }
 
+  if (select_lex->olap == ROLLUP_TYPE && rollup_process_const_fields())
+  {
+    DBUG_PRINT("error", ("Error: rollup_process_fields() failed"));
+    DBUG_RETURN(1);
+  }
+
   /* Remove distinct if only const tables */
   select_distinct= select_distinct && (const_tables != tables);
   thd_proc_info(thd, "preparing");
@@ -1043,7 +1049,7 @@ JOIN::optimize()
        join_tab[const_tables].select->quick->get_type() != 
        QUICK_SELECT_I::QS_TYPE_GROUP_MIN_MAX))
   {
-    if (group_list &&
+    if (group_list && rollup.state == ROLLUP::STATE_NONE &&
        list_contains_unique_index(join_tab[const_tables].table,
                                  find_field_in_order_list,
                                  (void *) group_list))
@@ -1081,7 +1087,8 @@ JOIN::optimize()
     if (! hidden_group_fields && rollup.state == ROLLUP::STATE_NONE)
       select_distinct=0;
   }
-  else if (select_distinct && tables - const_tables == 1)
+  else if (select_distinct && tables - const_tables == 1 &&
+           rollup.state == ROLLUP::STATE_NONE)
   {
     /*
       We are only using one table. In this case we change DISTINCT to a
@@ -9858,6 +9865,7 @@ create_tmp_table(THD *thd,TMP_TABLE_PARAM *param,List<Item> &fields,
     for (; cur_group ; cur_group= cur_group->next, key_part_info++)
     {
       Field *field=(*cur_group->item)->get_tmp_table_field();
+      DBUG_ASSERT(field->table == table);
       bool maybe_null=(*cur_group->item)->maybe_null;
       key_part_info->null_bit=0;
       key_part_info->field=  field;
@@ -14992,32 +15000,7 @@ bool JOIN::rollup_init()
       {
         item->maybe_null= 1;
         found_in_group= 1;
-        if (item->const_item())
-        {
-          /*
-            For ROLLUP queries each constant item referenced in GROUP BY list
-            is wrapped up into an Item_func object yielding the same value
-            as the constant item. The objects of the wrapper class are never
-            considered as constant items and besides they inherit all
-            properties of the Item_result_field class.
-            This wrapping allows us to ensure writing constant items
-            into temporary tables whenever the result of the ROLLUP
-            operation has to be written into a temporary table, e.g. when
-            ROLLUP is used together with DISTINCT in the SELECT list.
-            Usually when creating temporary tables for a intermidiate
-            result we do not include fields for constant expressions.
-	  */           
-          Item* new_item= new Item_func_rollup_const(item);
-          if (!new_item)
-            return 1;
-          new_item->fix_fields(thd, (Item **) 0);
-          thd->change_item_tree(it.ref(), new_item);
-          for (ORDER *tmp= group_tmp; tmp; tmp= tmp->next)
-          { 
-            if (*tmp->item == item)
-              thd->change_item_tree(tmp->item, new_item);
-          }
-        }
+        break;
       }
     }
     if (item->type() == Item::FUNC_ITEM && !found_in_group)
@@ -15036,6 +15019,59 @@ bool JOIN::rollup_init()
   }
   return 0;
 }
+
+/**
+   Wrap all constant Items in GROUP BY list.
+
+   For ROLLUP queries each constant item referenced in GROUP BY list
+   is wrapped up into an Item_func object yielding the same value
+   as the constant item. The objects of the wrapper class are never
+   considered as constant items and besides they inherit all
+   properties of the Item_result_field class.
+   This wrapping allows us to ensure writing constant items
+   into temporary tables whenever the result of the ROLLUP
+   operation has to be written into a temporary table, e.g. when
+   ROLLUP is used together with DISTINCT in the SELECT list.
+   Usually when creating temporary tables for a intermidiate
+   result we do not include fields for constant expressions.
+
+   @retval
+     0  if ok
+   @retval
+     1  on error
+*/
+
+bool JOIN::rollup_process_const_fields()
+{
+  ORDER *group_tmp;
+  Item *item;
+  List_iterator<Item> it(all_fields);
+
+  for (group_tmp= group_list; group_tmp; group_tmp= group_tmp->next)
+  {
+    if (!(*group_tmp->item)->const_item())
+      continue;
+    while ((item= it++))
+    {
+      if (*group_tmp->item == item)
+      {
+        Item* new_item= new Item_func_rollup_const(item);
+        if (!new_item)
+          return 1;
+        new_item->fix_fields(thd, (Item **) 0);
+        thd->change_item_tree(it.ref(), new_item);
+        for (ORDER *tmp= group_tmp; tmp; tmp= tmp->next)
+        {
+          if (*tmp->item == item)
+            thd->change_item_tree(tmp->item, new_item);
+        }
+        break;
+      }
+    }
+    it.rewind();
+  }
+  return 0;
+}
   
 
 /*

sql/sql_select.h

@@ -452,6 +452,7 @@ public:
   }
 
   bool rollup_init();
+  bool rollup_process_const_fields();
   bool rollup_make_fields(List<Item> &all_fields, List<Item> &fields,
 			  Item_sum ***func);
   int rollup_send_data(uint idx);