Fix LP BUG#682683

  
Analysis:
The fix for LP BUG#680846 avoids evaluation of constant expressions
with subqueries in the GROUP/ORDER clauses in the procedure
remove_const(). The purpose of remove_const is to remove constant
expressions in the GROUP/ORDER clauses.
  
In order delay until execution the evaluation of such subqueries,
they were not removed in the GROUP/ORDER clause. As a result temp
table creation during execution attempted to create a column in the
temp table for each constant GROUP/ORDER expression. However, the
logic in create_tmp_table is to not create temp table columns for
constant items. The crash was due to a group Item without a
corresponding column in the temp table for GROUP BY.
  
Solution:
The patch adds back removal of constant expressions with subqueries.
In order for such expressions to be evaluated, so that the server can
ensure that such subquries return 1 row, the evaluation of these
expressions is delayed until execution.

mysql-test/r/subselect4.result

@@ -605,6 +605,46 @@ COUNT(t2.f3)	f9
 0	NULL
 drop table t1,t2;
 #
+# LP BUG#682683 Crash in create_tmp_table called from
+#               JOIN::init_execution
+#
+CREATE TABLE t2 (f1 int) ;
+INSERT INTO t2 VALUES (1),(2);
+CREATE TABLE t1 (f1 int) ;
+EXPLAIN
+SELECT (SELECT f1 FROM t1) AS field1 FROM t2 GROUP BY field1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	
+2	SUBQUERY	t1	system	NULL	NULL	NULL	NULL	0	const row not found
+SELECT (SELECT f1 FROM t1) AS field1 FROM t2 GROUP BY field1;
+field1
+NULL
+EXPLAIN
+SELECT (SELECT f1 FROM t1) AS field1 FROM t2 ORDER BY field1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	
+2	SUBQUERY	t1	system	NULL	NULL	NULL	NULL	0	const row not found
+SELECT (SELECT f1 FROM t1) AS field1 FROM t2 ORDER BY field1;
+field1
+NULL
+NULL
+INSERT INTO t1 VALUES (1),(2);
+EXPLAIN
+SELECT (SELECT f1 FROM t1) AS field1 FROM t2 GROUP BY field1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	
+2	SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	2	
+SELECT (SELECT f1 FROM t1) AS field1 FROM t2 GROUP BY field1;
+ERROR 21000: Subquery returns more than 1 row
+EXPLAIN
+SELECT (SELECT f1 FROM t1) AS field1 FROM t2 ORDER BY field1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	
+2	SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	2	
+SELECT (SELECT f1 FROM t1) AS field1 FROM t2 ORDER BY field1;
+ERROR 21000: Subquery returns more than 1 row
+drop table t1,t2;
+#
 # LP BUG#680943 Assertion `!table || (!table->read_set ||
 # bitmap_is_set(table->read_set, field_index))' failed with subquery
 #

mysql-test/t/subselect4.test

@@ -558,6 +558,36 @@ ORDER BY f9;
 
 drop table t1,t2;
 
+--echo #
+--echo # LP BUG#682683 Crash in create_tmp_table called from
+--echo #               JOIN::init_execution
+--echo #
+
+CREATE TABLE t2 (f1 int) ;
+INSERT INTO t2 VALUES (1),(2);
+
+CREATE TABLE t1 (f1 int) ;
+
+EXPLAIN
+SELECT (SELECT f1 FROM t1) AS field1 FROM t2 GROUP BY field1;
+SELECT (SELECT f1 FROM t1) AS field1 FROM t2 GROUP BY field1;
+EXPLAIN
+SELECT (SELECT f1 FROM t1) AS field1 FROM t2 ORDER BY field1;
+SELECT (SELECT f1 FROM t1) AS field1 FROM t2 ORDER BY field1;
+
+INSERT INTO t1 VALUES (1),(2);
+
+EXPLAIN
+SELECT (SELECT f1 FROM t1) AS field1 FROM t2 GROUP BY field1;
+--error ER_SUBQUERY_NO_1_ROW
+SELECT (SELECT f1 FROM t1) AS field1 FROM t2 GROUP BY field1;
+EXPLAIN
+SELECT (SELECT f1 FROM t1) AS field1 FROM t2 ORDER BY field1;
+--error ER_SUBQUERY_NO_1_ROW
+SELECT (SELECT f1 FROM t1) AS field1 FROM t2 ORDER BY field1;
+
+drop table t1,t2;
+
 --echo #
 --echo # LP BUG#680943 Assertion `!table || (!table->read_set ||
 --echo # bitmap_is_set(table->read_set, field_index))' failed with subquery

sql/sql_select.cc

@@ -1402,6 +1402,7 @@ setup_subq_exit:
 
 /**
   Create and initialize objects neeed for the execution of a query plan.
+  Evaluate constant expressions not evaluated during optimization.
 */
 
 int JOIN::init_execution()
@@ -1409,6 +1410,7 @@ int JOIN::init_execution()
   DBUG_ENTER("JOIN::init_execution");
 
   DBUG_ASSERT(optimized);
+  DBUG_ASSERT(!(select_options & SELECT_DESCRIBE));
   initialized= true;
 
   /* Create a tmp table if distinct or if the sort is too complicated */
@@ -1839,6 +1841,27 @@ JOIN::exec()
     DBUG_VOID_RETURN;
   }
 
+  /*
+    Evaluate all constant expressions with subqueries in the ORDER/GROUP clauses
+    to make sure that all subqueries return a single row. The evaluation itself
+    will trigger an error if that is not the case.
+  */
+  if (exec_const_order_group_cond.elements &&
+      !(select_options & SELECT_DESCRIBE))
+  {
+    List_iterator_fast<Item> const_item_it(exec_const_order_group_cond);
+    Item *cur_const_item;
+    while ((cur_const_item= const_item_it++))
+    {
+      cur_const_item->val_str(&cur_const_item->str_value);
+      if (thd->is_error())
+      {
+        error= thd->is_error();
+        DBUG_VOID_RETURN;
+      }
+    }
+  }
+
   if ((this->select_lex->options & OPTION_SCHEMA_TABLE) &&
       get_schema_tables_result(this, PROCESSED_BY_JOIN_EXEC))
     DBUG_VOID_RETURN;
@@ -8279,13 +8302,16 @@ remove_const(JOIN *join,ORDER *first_order, COND *cond,
         (join->tables > 1 && join->rollup.state == ROLLUP::STATE_INITED &&
         join->outer_join))
       *simple_order=0;				// Must do a temp table to sort
-    else if (!(order_tables & not_const_tables) &&
-             !order->item[0]->with_subselect)
+    else if (!(order_tables & not_const_tables))
     {
-      /*
-        Skip constant expressions in the ORDER/GROUP clause, except when there
-        is a subquery in the expression.
-      */
+      if (order->item[0]->with_subselect)
+      {
+        /*
+          Delay the evaluation of constant ORDER and/or GROUP expressions that
+          contain subqueries until the execution phase.
+        */
+        join->exec_const_order_group_cond.push_back(order->item[0]);
+      }
       DBUG_PRINT("info",("removing: %s", order->item[0]->full_name()));
       continue;
     }

sql/sql_select.h

@@ -1599,6 +1599,13 @@ public:
     evaluated at optimization time.
   */
   Item *exec_const_cond;
+  /*
+    Constant ORDER and/or GROUP expressions that contain subqueries. Such
+    expressions need to evaluated to verify that the subquery indeed
+    returns a single row. The evaluation of such expressions is delayed
+    until query execution.
+  */
+  List<Item> exec_const_order_group_cond;
   SQL_SELECT *select;                ///<created in optimisation phase
   JOIN_TAB *return_tab;              ///<used only for outer joins
   Item **ref_pointer_array; ///<used pointer reference for this select
@@ -1762,7 +1769,8 @@ public:
   bool send_row_on_empty_set()
   {
     return (do_send_rows && tmp_table_param.sum_func_count != 0 &&
-	    !group_list && having_value != Item::COND_FALSE);
+	    !(group_list || group_optimized_away) &&
+            having_value != Item::COND_FALSE);
   }
   bool change_result(select_result *result);
   bool is_top_level_join() const