Bug#20836 Selecting into variables results in wrong results being returned

This error is displayed anytime the SELECT statement needs a temp table to
return correct results because the object (select_dumpvar) that represents
variables named in the INTO clause stored the results before the temp
table was considered.  The problem was fixed by creating the necessary
Item_func_set_user_var objects once the correct data is ready.

mysql-test/r/distinct.result

@@ -566,3 +566,62 @@ a	b
 3	2
 2	3
 DROP TABLE t1;
+DROP TABLE IF EXISTS t1;
+CREATE TABLE t1 (id INT NOT NULL, fruit_id INT NOT NULL, fruit_name varchar(20)
+default NULL);
+INSERT INTO t1 VALUES (1,1,'ORANGE');
+INSERT INTO t1 VALUES (2,2,'APPLE');
+INSERT INTO t1 VALUES (3,2,'APPLE');
+INSERT INTO t1 VALUES (4,3,'PEAR');
+SELECT DISTINCT fruit_id, fruit_name INTO @v1, @v2 FROM t1 WHERE fruit_name = 
+'APPLE';
+SELECT @v1, @v2;
+@v1	@v2
+2	APPLE
+SELECT DISTINCT fruit_id, fruit_name INTO @v3, @v4 FROM t1 GROUP BY fruit_id, 
+fruit_name HAVING fruit_name = 'APPLE';
+SELECT @v3, @v4;
+@v3	@v4
+2	APPLE
+SELECT DISTINCT @v5:= fruit_id, @v6:= fruit_name INTO @v7, @v8 FROM t1 WHERE 
+fruit_name = 'APPLE';
+SELECT @v5, @v6, @v7, @v8;
+@v5	@v6	@v7	@v8
+2	APPLE	2	APPLE
+SELECT DISTINCT @v5 + fruit_id, CONCAT(@v6, fruit_name) INTO @v9, @v10 FROM t1 
+WHERE fruit_name = 'APPLE';
+SELECT @v5, @v6, @v7, @v8, @v9, @v10;
+@v5	@v6	@v7	@v8	@v9	@v10
+2	APPLE	2	APPLE	4	APPLEAPPLE
+SELECT DISTINCT @v11:= @v5 + fruit_id, @v12:= CONCAT(@v6, fruit_name) INTO 
+@v13, @v14 FROM t1 WHERE fruit_name = 'APPLE';
+SELECT @v11, @v12, @v13, @v14;
+@v11	@v12	@v13	@v14
+4	APPLEAPPLE	4	APPLEAPPLE
+SELECT DISTINCT @v13, @v14 INTO @v15, @v16 FROM t1 WHERE fruit_name = 'APPLE';
+SELECT @v15, @v16;
+@v15	@v16
+4	APPLEAPPLE
+SELECT DISTINCT 2 + 2, 'Bob' INTO @v17, @v18 FROM t1 WHERE fruit_name = 
+'APPLE';
+SELECT @v17, @v18;
+@v17	@v18
+4	Bob
+DROP TABLE IF EXISTS t2;
+CREATE TABLE t2 (fruit_id INT NOT NULL, fruit_name varchar(20)
+default NULL);
+SELECT DISTINCT fruit_id, fruit_name INTO OUTFILE 
+'../tmp/data1.tmp' FROM t1 WHERE fruit_name = 'APPLE';
+LOAD DATA INFILE '../tmp/data1.tmp' INTO TABLE t2;
+SELECT DISTINCT @v19:= fruit_id, @v20:= fruit_name INTO OUTFILE 
+'../tmp/data2.tmp' FROM t1 WHERE fruit_name = 'APPLE';
+LOAD DATA INFILE '../tmp/data2.tmp' INTO TABLE t2;
+SELECT @v19, @v20;
+@v19	@v20
+2	APPLE
+SELECT * FROM t2;
+fruit_id	fruit_name
+2	APPLE
+2	APPLE
+DROP TABLE t1;
+DROP TABLE t2;

mysql-test/t/distinct.test

@@ -389,4 +389,69 @@ explain SELECT DISTINCT a, b FROM t1 ORDER BY b;
 SELECT DISTINCT a, b FROM t1 ORDER BY b;
 DROP TABLE t1;
 
+#
+#Bug #20836: Selecting into variables results in wrong results being returned
+#
+--disable_warnings
+DROP TABLE IF EXISTS t1;
+--enable_warnings
+
+CREATE TABLE t1 (id INT NOT NULL, fruit_id INT NOT NULL, fruit_name varchar(20)
+default NULL);
+
+INSERT INTO t1 VALUES (1,1,'ORANGE');
+INSERT INTO t1 VALUES (2,2,'APPLE');
+INSERT INTO t1 VALUES (3,2,'APPLE');
+INSERT INTO t1 VALUES (4,3,'PEAR');
+
+SELECT DISTINCT fruit_id, fruit_name INTO @v1, @v2 FROM t1 WHERE fruit_name = 
+'APPLE';
+SELECT @v1, @v2;
+
+SELECT DISTINCT fruit_id, fruit_name INTO @v3, @v4 FROM t1 GROUP BY fruit_id, 
+fruit_name HAVING fruit_name = 'APPLE';
+SELECT @v3, @v4;
+
+SELECT DISTINCT @v5:= fruit_id, @v6:= fruit_name INTO @v7, @v8 FROM t1 WHERE 
+fruit_name = 'APPLE';
+SELECT @v5, @v6, @v7, @v8;
+
+SELECT DISTINCT @v5 + fruit_id, CONCAT(@v6, fruit_name) INTO @v9, @v10 FROM t1 
+WHERE fruit_name = 'APPLE';
+SELECT @v5, @v6, @v7, @v8, @v9, @v10;
+
+SELECT DISTINCT @v11:= @v5 + fruit_id, @v12:= CONCAT(@v6, fruit_name) INTO 
+@v13, @v14 FROM t1 WHERE fruit_name = 'APPLE';
+SELECT @v11, @v12, @v13, @v14;
+
+SELECT DISTINCT @v13, @v14 INTO @v15, @v16 FROM t1 WHERE fruit_name = 'APPLE';
+SELECT @v15, @v16;
+
+SELECT DISTINCT 2 + 2, 'Bob' INTO @v17, @v18 FROM t1 WHERE fruit_name = 
+'APPLE';
+SELECT @v17, @v18;
+
+--disable_warnings
+DROP TABLE IF EXISTS t2;
+--enable_warnings
+
+CREATE TABLE t2 (fruit_id INT NOT NULL, fruit_name varchar(20)
+default NULL);
+
+SELECT DISTINCT fruit_id, fruit_name INTO OUTFILE 
+'../tmp/data1.tmp' FROM t1 WHERE fruit_name = 'APPLE';
+LOAD DATA INFILE '../tmp/data1.tmp' INTO TABLE t2;
+--exec rm $MYSQL_TEST_DIR/var/tmp/data1.tmp
+
+SELECT DISTINCT @v19:= fruit_id, @v20:= fruit_name INTO OUTFILE 
+'../tmp/data2.tmp' FROM t1 WHERE fruit_name = 'APPLE';
+LOAD DATA INFILE '../tmp/data2.tmp' INTO TABLE t2;
+--exec rm $MYSQL_TEST_DIR/var/tmp/data2.tmp
+
+SELECT @v19, @v20;
+SELECT * FROM t2;
+
+DROP TABLE t1;
+DROP TABLE t2;
+
 # End of 4.1 tests

sql/sql_class.cc

@@ -1372,37 +1372,20 @@ bool select_exists_subselect::send_data(List<Item> &items)
 
 int select_dumpvar::prepare(List<Item> &list, SELECT_LEX_UNIT *u)
 {
-  List_iterator_fast<Item> li(list);
-  List_iterator_fast<LEX_STRING> gl(var_list);
-  Item *item;
-  LEX_STRING *ls;
+  unit= u;
+  
   if (var_list.elements != list.elements)
   {
     my_error(ER_WRONG_NUMBER_OF_COLUMNS_IN_SELECT, MYF(0));
     return 1;
   }
-  unit=u;
-  while ((item=li++))
-  {
-    ls= gl++;
-    Item_func_set_user_var *xx = new Item_func_set_user_var(*ls,item);
-    /*
-      Item_func_set_user_var can't substitute something else on its place =>
-      0 can be passed as last argument (reference on item)
-    */
-    xx->fix_fields(thd,(TABLE_LIST*) thd->lex->select_lex.table_list.first,
-		   0);
-    xx->fix_length_and_dec();
-    vars.push_back(xx);
-  }
   return 0;
 }
 
 
 void select_dumpvar::cleanup()
 {
-  vars.empty();
-  row_count=0;
+  row_count= 0;
 }
 
 
@@ -1744,12 +1727,14 @@ Statement_map::~Statement_map()
 
 bool select_dumpvar::send_data(List<Item> &items)
 {
-  List_iterator_fast<Item_func_set_user_var> li(vars);
-  Item_func_set_user_var *xx;
+  List_iterator_fast<LEX_STRING> var_li(var_list);
+  List_iterator<Item> it(items);
+  Item *item;
+  LEX_STRING *ls;
   DBUG_ENTER("send_data");
 
   if (unit->offset_limit_cnt)
-  {				          // Using limit offset,count
+  {						// using limit offset,count
     unit->offset_limit_cnt--;
     DBUG_RETURN(0);
   }
@@ -1758,10 +1743,21 @@ bool select_dumpvar::send_data(List<Item> &items)
     my_error(ER_TOO_MANY_ROWS, MYF(0));
     DBUG_RETURN(1);
   }
-  while ((xx=li++))
+  while ((ls= var_li++) && (item= it++))
   {
-    xx->check();
-    xx->update();
+    Item_func_set_user_var *suv= new Item_func_set_user_var(*ls, item);
+
+    /*
+      Item_func_set_user_var can't substitute something else on its
+      place => NULL may be passed as last argument (reference on
+      item) Item_func_set_user_var can't be fixed after creation, so
+      we do not check var->fixed
+    */
+
+    suv->fix_fields(thd, (TABLE_LIST *) thd->lex->select_lex.table_list.first,
+            0);
+    suv->check();
+    suv->update();  
   }
   DBUG_RETURN(0);
 }

sql/sql_class.h

@@ -1573,8 +1573,7 @@ class select_dumpvar :public select_result_interceptor {
   ha_rows row_count;
 public:
   List<LEX_STRING> var_list;
-  List<Item_func_set_user_var> vars;
-  select_dumpvar(void)  { var_list.empty(); vars.empty(); row_count=0;}
+  select_dumpvar()  { var_list.empty(); row_count= 0;}
   ~select_dumpvar() {}
   int prepare(List<Item> &list, SELECT_LEX_UNIT *u);
   bool send_data(List<Item> &items);