Fix for LP BUG#806071

In case of two views with subqueries it is dificult to decide about order of injected ORDER BY clauses.
A simple solution is just prohibit ORDER BY injection if there is other order by.

mysql-test/r/view.result:
  New test added, old test changed.
mysql-test/t/view.test:
  New test aded.
sql/share/errmsg.txt:
  new warning added.
sql/sql_view.cc:
  Inject ORDER BY only if there is no other one.
  
  Warning about ignoring ORDER BY in this case for EXPLAIN EXTENDED.

mysql-test/r/view.result

@@ -3135,17 +3135,18 @@ Warnings:
 Note	1003	select `test`.`t1`.`f1` AS `f1`,`test`.`t1`.`f2` AS `f2` from `test`.`t1` order by `test`.`t1`.`f2`
 select * from v1 order by f1;
 f1	f2
-1	1
 1	2
 1	3
+1	1
+2	3
 2	1
 2	2
-2	3
 explain extended select * from v1 order by f1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	6	100.00	Using filesort
 Warnings:
-Note	1003	select `test`.`t1`.`f1` AS `f1`,`test`.`t1`.`f2` AS `f2` from `test`.`t1` order by `test`.`t1`.`f1`,`test`.`t1`.`f2`
+Note	1926	View 'test'.'v1' ORDER BY clause ignored because there is other ORDER BY clause already.
+Note	1003	select `test`.`t1`.`f1` AS `f1`,`test`.`t1`.`f2` AS `f2` from `test`.`t1` order by `test`.`t1`.`f1`
 drop view v1;
 drop table t1;
 CREATE TABLE t1 (
@@ -4310,5 +4311,29 @@ f1	f2	f3	f4
 EXECUTE stmt1;
 f1	f2	f3	f4
 DEALLOCATE PREPARE stmt1;
+#
+# LP BUG#806071 (2 views with ORDER BY)
+#
 DROP VIEW v1;
 DROP TABLE t1;
+CREATE TABLE t1 (f1 int);
+INSERT INTO t1 VALUES (1),(1);
+CREATE ALGORITHM=TEMPTABLE VIEW v1 AS SELECT f1 FROM t1;
+CREATE ALGORITHM=MERGE VIEW v2 AS SELECT f1 FROM v1 ORDER BY f1;
+SELECT * FROM v2 AS a1, v2 AS a2;
+f1	f1
+1	1
+1	1
+1	1
+1	1
+EXPLAIN EXTENDED SELECT * FROM v2 AS a1, v2 AS a2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	<derived3>	ALL	NULL	NULL	NULL	NULL	2	100.00	Using temporary; Using filesort
+1	SIMPLE	<derived5>	ALL	NULL	NULL	NULL	NULL	2	100.00	Using join buffer (flat, BNL join)
+5	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	
+3	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	
+Warnings:
+Note	1926	View 'test'.'v2' ORDER BY clause ignored because there is other ORDER BY clause already.
+Note	1003	select `v1`.`f1` AS `f1`,`v1`.`f1` AS `f1` from `test`.`v1` join `test`.`v1` order by `v1`.`f1`
+drop view v1, v2;
+drop table t1;

mysql-test/t/view.test

@@ -4253,5 +4253,21 @@ EXECUTE stmt1;
 
 DEALLOCATE PREPARE stmt1;
 
+--echo #
+--echo # LP BUG#806071 (2 views with ORDER BY)
+--echo #
+
 DROP VIEW v1;
 DROP TABLE t1;
+
+CREATE TABLE t1 (f1 int);
+INSERT INTO t1 VALUES (1),(1);
+
+CREATE ALGORITHM=TEMPTABLE VIEW v1 AS SELECT f1 FROM t1;
+CREATE ALGORITHM=MERGE VIEW v2 AS SELECT f1 FROM v1 ORDER BY f1;
+
+SELECT * FROM v2 AS a1, v2 AS a2;
+EXPLAIN EXTENDED SELECT * FROM v2 AS a1, v2 AS a2;
+
+drop view v1, v2;
+drop table t1;

sql/share/errmsg.txt

@@ -6288,3 +6288,5 @@ ER_QUERY_CACHE_IS_DISABLED
         eng "Query cache is disabled (resize or similar command in progress); repeat this command later"
 ER_QUERY_CACHE_IS_GLOBALY_DISABLED
         eng "Query cache is globally disabled and you can't enable it only for this session"
+ER_VIEW_ORDERBY_IGNORED
+        eng "View '%-.192s'.'%-.192s' ORDER BY clause ignored because there is other ORDER BY clause already."

sql/sql_view.cc

@@ -1483,8 +1483,22 @@ bool mysql_make_view(THD *thd, File_parser *parser, TABLE_LIST *table,
         We can safely ignore the VIEW's ORDER BY if we merge into union 
         branch, as order is not important there.
       */
-      if (!table->select_lex->master_unit()->is_union())
+      if (!table->select_lex->master_unit()->is_union() &&
+          table->select_lex->order_list.elements == 0)
         table->select_lex->order_list.push_back(&lex->select_lex.order_list);
+      else
+      {
+        if (old_lex->sql_command == SQLCOM_SELECT &&
+            (old_lex->describe & DESCRIBE_EXTENDED) &&
+            lex->select_lex.order_list.elements &&
+            !table->select_lex->master_unit()->is_union())
+        {
+          push_warning_printf(thd, MYSQL_ERROR::WARN_LEVEL_NOTE,
+                              ER_VIEW_ORDERBY_IGNORED,
+                              ER(ER_VIEW_ORDERBY_IGNORED),
+                              table->db, table->table_name);
+        }
+      }
       /*
 	This SELECT_LEX will be linked in global SELECT_LEX list
 	to make it processed by mysql_handle_derived(),