Bug#48508: Crash on prepared statement re-execution.

Actually there is two different bugs.
The first one caused crash on queries with WHERE condition over views
containing WHERE condition. A wrong check for prepared statement phase led
to items for view fields being allocated in the execution memory and freed
at the end of execution. Thus the optimized WHERE condition refers to
unallocated memory on the second execution and server crashed.
The second one caused by the Item_cond::compile function not saving changes
it made to the item tree. Thus on the next execution changes weren't
reverted and server crashed on dereferencing of unallocated space.

The new helper function called is_stmt_prepare_or_first_stmt_execute
is added to the Query_arena class.
The find_field_in_view function now uses
is_stmt_prepare_or_first_stmt_execute() to check whether
newly created view items should be freed at the end of the query execution.
The Item_cond::compile function now saves changes it makes to item tree.

mysql-test/r/ps.result

@@ -1891,4 +1891,27 @@ execute stmt using @arg;
 ?
 -12345.5432100000
 deallocate prepare stmt;
+#
+# Bug#48508: Crash on prepared statement re-execution.
+#
+create table t1(b int);
+insert into t1 values (0);
+create view v1 AS select 1 as a from t1 where b;
+prepare stmt from "select * from v1 where a";
+execute stmt;
+a
+execute stmt;
+a
+drop table t1;
+drop view v1;
+create table t1(a bigint);
+create table t2(b tinyint);
+insert into t2 values (null);
+prepare stmt from "select 1 from t1 join  t2 on a xor b where b > 1  and a =1";
+execute stmt;
+1
+execute stmt;
+1
+drop table t1,t2;
+#
 End of 5.0 tests.

mysql-test/t/ps.test

@@ -1973,4 +1973,25 @@ select @arg;
 execute stmt using @arg;
 deallocate prepare stmt;
 
+--echo #
+--echo # Bug#48508: Crash on prepared statement re-execution.
+--echo #
+create table t1(b int);
+insert into t1 values (0);
+create view v1 AS select 1 as a from t1 where b;
+prepare stmt from "select * from v1 where a";
+execute stmt;
+execute stmt;
+drop table t1;
+drop view v1;
+
+create table t1(a bigint);
+create table t2(b tinyint);
+insert into t2 values (null);
+prepare stmt from "select 1 from t1 join  t2 on a xor b where b > 1  and a =1";
+execute stmt;
+execute stmt;
+drop table t1,t2;
+--echo #
+
 --echo End of 5.0 tests.

sql/item_cmpfunc.cc

@@ -3907,7 +3907,7 @@ Item *Item_cond::compile(Item_analyzer analyzer, byte **arg_p,
     byte *arg_v= *arg_p;
     Item *new_item= item->compile(analyzer, &arg_v, transformer, arg_t);
     if (new_item && new_item != item)
-      li.replace(new_item);
+      current_thd->change_item_tree(li.ref(), new_item);
   }
   return Item_func::transform(transformer, arg_t);
 }

sql/sql_base.cc

@@ -3481,7 +3481,8 @@ find_field_in_view(THD *thd, TABLE_LIST *table_list,
     if (!my_strcasecmp(system_charset_info, field_it.name(), name))
     {
       // in PS use own arena or data will be freed after prepare
-      if (register_tree_change && thd->stmt_arena->is_stmt_prepare_or_first_sp_execute())
+      if (register_tree_change &&
+          thd->stmt_arena->is_stmt_prepare_or_first_stmt_execute())
         arena= thd->activate_stmt_arena_if_needed(&backup);
       /*
         create_item() may, or may not create a new Item, depending on

sql/sql_class.h

@@ -759,6 +759,8 @@ class Query_arena
   { return state == INITIALIZED_FOR_SP; }
   inline bool is_stmt_prepare_or_first_sp_execute() const
   { return (int)state < (int)PREPARED; }
+  inline bool is_stmt_prepare_or_first_stmt_execute() const
+  { return (int)state <= (int)PREPARED; }
   inline bool is_first_stmt_execute() const { return state == PREPARED; }
   inline bool is_stmt_execute() const
   { return state == PREPARED || state == EXECUTED; }