Fix for BUG#8490: In mysql_make_view for join algorithm views we need

to insert view's subqueries into select_lex->slave(->next)* chain. 
In case a join has several such views, don't add the same subqueries several times
(this forms a loop on the above chain which breaks many parts of the code)

mysql-test/r/view.result

@@ -1694,3 +1694,21 @@ col1	col2	col2	col3
 5	david	NULL	NULL
 DROP VIEW v1,v2,v3;
 DROP TABLE t1,t2;
+create table t1 as select 1 A union select 2 union select 3;
+create table t2 as select * from t1;
+create view v1 as select * from t1 where a in (select * from t2);
+select * from v1 A, v1 B where A.a = B.a;
+A	A
+1	1
+2	2
+3	3
+create table t3 as select a a,a b from t2;
+create view v2 as select * from t3 where 
+a in (select * from t1) or b in (select * from t2);
+select * from v2 A, v2 B where A.a = B.b;
+a	b	a	b
+1	1	1	1
+2	2	2	2
+3	3	3	3
+drop view v1, v2;
+drop table t1, t2, t3;

mysql-test/t/view.test

@@ -1519,3 +1519,17 @@ SELECT a.col1,a.col2,b.col2,b.col3
  
 DROP VIEW v1,v2,v3;
 DROP TABLE t1,t2;
+
+# BUG#8490 Select from views containing subqueries causes server to hang 
+# forever.
+create table t1 as select 1 A union select 2 union select 3;
+create table t2 as select * from t1;
+create view v1 as select * from t1 where a in (select * from t2);
+select * from v1 A, v1 B where A.a = B.a;
+create table t3 as select a a,a b from t2;
+create view v2 as select * from t3 where 
+  a in (select * from t1) or b in (select * from t2);
+select * from v2 A, v2 B where A.a = B.b;
+drop view v1, v2;
+drop table t1, t2, t3;
+

sql/sql_view.cc

@@ -796,17 +796,25 @@ mysql_make_view(File_parser *parser, TABLE_LIST *table)
 
       /* Store WHERE clause for post-processing in setup_ancestor */
       table->where= view_select->where;
-
       /*
-        Add subqueries units to SELECT in which we merging current view.
-
+        Add subqueries units to SELECT into which we merging current view.
+        
+        unit(->next)* chain starts with subqueries that are used by this
+        view and continues with subqueries that are used by other views.
+        We must not add any subquery twice (otherwise we'll form a loop),
+        to do this we remember in end_unit the first subquery that has 
+        been already added.
+                
         NOTE: we do not support UNION here, so we take only one select
       */
+      SELECT_LEX_NODE *end_unit= table->select_lex->slave;
       for (SELECT_LEX_UNIT *unit= lex->select_lex.first_inner_unit();
            unit;
            unit= unit->next_unit())
       {
         SELECT_LEX_NODE *save_slave= unit->slave;
+        if (unit == end_unit)
+          break;
         unit->include_down(table->select_lex);
         unit->slave= save_slave; // fix include_down initialisation
       }