Fix for bug#4912 "mysqld crashs in case a statement is executed

 a second time". The bug was caused by incompatibility of
negations elimination algorithm and PS: during first statement 
execute a subtree with negation was replaced with equivalent 
subtree without NOTs.
The problem was that although this transformation was permanent, 
items of the new subtree were created in execute-local memory.
The patch adds means to check if it is the first execute of a
prepared statement, and if this is the case, to allocate items
in memory of the prepared statement.
The implementation:
- backports Item_arena from 5.0
- adds Item_arena::is_stmt_prepare(), 
  Item_arena::is_first_stmt_execute().
- deletes THD::allocate_temporary_pool_for_ps_preparing(),
  THD::free_temporary_pool_for_ps_preparing(); they
  were redundant.
and adds a few invariants:
- thd->free_list never contains junk (= freed items)
- thd->current_arena is never null. If there is no
  prepared statement, it points at the thd. 
The rest of the patch contains mainly mechanical changes and
cleanups.


mysql-test/r/ps.result:
  Test results updated (test case for Bug#4912)
mysql-test/t/ps.test:
  A test case for Bug#4912 "mysqld crashs in case a statement is 
  executed a second time"
sql/item_cmpfunc.cc:
  current_statement -> current_arena
sql/item_subselect.cc:
  Statement -> Item_arena, current_statement -> current_arena
sql/item_subselect.h:
  Item_subselect does not need to save thd->current_statement.
sql/item_sum.cc:
  Statement -> Item_arena
sql/item_sum.h:
  Statement -> Item_arena
sql/mysql_priv.h:
  Statement -> Item_arena
sql/sql_base.cc:
  current_statement -> current_arena
sql/sql_class.cc:
  - Item_arena
  - convenient set_n_backup_statement, restore_backup_statement
  (nice idea, Sanja)
sql/sql_class.h:
  - Item_arena: backport from 5.0
  - allocate_temporary_pool_for_ps_preparing,
    free_temporary_pool_for_ps_preparing removed.
sql/sql_derived.cc:
  current_statement -> current_arena
sql/sql_lex.cc:
  current_statement -> current_arena
sql/sql_parse.cc:
  Deploy invariant that thd->free_list never contains junk items
  (backport from 5.0).
sql/sql_prepare.cc:
  - backporting Item_arena
  - no need to allocate_temporary_pool_for_ps_preparing().
sql/sql_select.cc:
  Fix for bug#4912 "mysqld crashs in case a statement is 
  executed a second time": if this is the first execute of
  a prepared statement, negation elimination is
  done in memory of the prepared statement.
sql/sql_union.cc:
  Backporting Item_arena from 5.0.

mysql-test/r/ps.result

@@ -219,3 +219,10 @@ Name	Engine	Version	Row_format	Rows	Avg_row_length	Data_length	Max_data_length	I
 t1	MyISAM	9	Dynamic	0	0	0	4294967295	1024	0	NULL	#	#	#	latin1_swedish_ci	NULL		
 deallocate prepare stmt1 ;
 drop table t1;
+create table t1(a varchar(2), b varchar(3));
+prepare stmt1 from "select a, b from t1 where (not (a='aa' and b < 'zzz'))";
+execute stmt1;
+a	b
+execute stmt1;
+a	b
+deallocate prepare stmt1;

mysql-test/t/ps.test

@@ -206,3 +206,15 @@ execute stmt1;
 show table status from test like 't1%' ;
 deallocate prepare stmt1 ;
 drop table t1;
+
+#
+# Bug#4912 "mysqld crashs in case a statement is executed a second time":
+# negation elimination should and prepared statemens
+# 
+
+create table t1(a varchar(2), b varchar(3));
+prepare stmt1 from "select a, b from t1 where (not (a='aa' and b < 'zzz'))";
+execute stmt1;
+execute stmt1;
+deallocate prepare stmt1;
+

sql/item_cmpfunc.cc

@@ -589,10 +589,8 @@ bool Item_in_optimizer::fix_left(THD *thd,
   /*
     If it is preparation PS only then we do not know values of parameters =>
     cant't get there values and do not need that values.
-
-    TODO: during merge with 5.0 it should be changed on !thd->only_prepare()
   */
-  if (!thd->current_statement)
+  if (! thd->current_arena->is_stmt_prepare())
     cache->store(args[0]);
   if (cache->cols() == 1)
   {

sql/item_subselect.cc

@@ -125,7 +125,6 @@ bool Item_subselect::fix_fields(THD *thd_param, TABLE_LIST *tables, Item **ref)
 {
   DBUG_ASSERT(fixed == 0);
   engine->set_thd((thd= thd_param));
-  stmt= thd->current_statement;
 
   char const *save_where= thd->where;
   int res;
@@ -306,7 +305,10 @@ Item_singlerow_subselect::select_transformer(JOIN *join)
     return RES_OK;
 
   SELECT_LEX *select_lex= join->select_lex;
-  Statement backup;
+
+  /* Juggle with current arena only if we're in prepared statement prepare */
+  Item_arena *arena= join->thd->current_arena;
+  Item_arena backup;
 
   if (!select_lex->master_unit()->first_select()->next_select() &&
       !select_lex->table_list.elements &&
@@ -341,8 +343,8 @@ Item_singlerow_subselect::select_transformer(JOIN *join)
     if (join->conds || join->having)
     {
       Item *cond;
-      if (stmt)
-	thd->set_n_backup_item_arena(stmt, &backup);
+      if (arena->is_stmt_prepare())
+	thd->set_n_backup_item_arena(arena, &backup);
 
       if (!join->having)
 	cond= join->conds;
@@ -355,15 +357,15 @@ Item_singlerow_subselect::select_transformer(JOIN *join)
 					   new Item_null())))
 	goto err;
     }
-    if (stmt)
-      thd->restore_backup_item_arena(stmt, &backup);
+    if (arena->is_stmt_prepare())
+      thd->restore_backup_item_arena(arena, &backup);
     return RES_REDUCE;
   }
   return RES_OK;
 
 err:
-  if (stmt)
-    thd->restore_backup_item_arena(stmt, &backup);
+  if (arena->is_stmt_prepare())
+    thd->restore_backup_item_arena(arena, &backup);
   return RES_ERROR;
 }
 
@@ -640,11 +642,11 @@ Item_in_subselect::single_value_transformer(JOIN *join,
   }
 
   SELECT_LEX *select_lex= join->select_lex;
-  Statement backup;
+  Item_arena *arena= join->thd->current_arena, backup;
 
   thd->where= "scalar IN/ALL/ANY subquery";
-  if (stmt)
-    thd->set_n_backup_item_arena(stmt, &backup);
+  if (arena->is_stmt_prepare())
+    thd->set_n_backup_item_arena(arena, &backup);
 
   if (select_lex->item_list.elements > 1)
   {
@@ -857,21 +859,21 @@ Item_in_subselect::single_value_transformer(JOIN *join,
 	  push_warning(thd, MYSQL_ERROR::WARN_LEVEL_NOTE,
 		       ER_SELECT_REDUCED, warn_buff);
 	}
-	if (stmt)
-	  thd->restore_backup_item_arena(stmt, &backup);
+	if (arena->is_stmt_prepare())
+	  thd->restore_backup_item_arena(arena, &backup);
 	DBUG_RETURN(RES_REDUCE);
       }
     }
   }
 
 ok:
-  if (stmt)
-    thd->restore_backup_item_arena(stmt, &backup);
+  if (arena->is_stmt_prepare())
+    thd->restore_backup_item_arena(arena, &backup);
   DBUG_RETURN(RES_OK);
 
 err:
-  if (stmt)
-    thd->restore_backup_item_arena(stmt, &backup);
+  if (arena->is_stmt_prepare())
+    thd->restore_backup_item_arena(arena, &backup);
   DBUG_RETURN(RES_ERROR);
 }
 
@@ -885,12 +887,12 @@ Item_in_subselect::row_value_transformer(JOIN *join)
   {
     DBUG_RETURN(RES_OK);
   }
-  Statement backup;
+  Item_arena *arena= join->thd->current_arena, backup;
   Item *item= 0;
 
   thd->where= "row IN/ALL/ANY subquery";
-  if (stmt)
-    thd->set_n_backup_item_arena(stmt, &backup);
+  if (arena->is_stmt_prepare())
+    thd->set_n_backup_item_arena(arena, &backup);
 
   SELECT_LEX *select_lex= join->select_lex;
 
@@ -974,13 +976,13 @@ Item_in_subselect::row_value_transformer(JOIN *join)
     if (join->conds->fix_fields(thd, join->tables_list, 0))
       goto err;
   }
-  if (stmt)
-    thd->restore_backup_item_arena(stmt, &backup);
+  if (arena->is_stmt_prepare())
+    thd->restore_backup_item_arena(arena, &backup);
   DBUG_RETURN(RES_OK);
 
 err:
-  if (stmt)
-    thd->restore_backup_item_arena(stmt, &backup);
+  if (arena->is_stmt_prepare())
+    thd->restore_backup_item_arena(arena, &backup);
   DBUG_RETURN(RES_ERROR);
 }
 

sql/item_subselect.h

@@ -36,8 +36,6 @@ class Item_subselect :public Item_result_field
 protected:
   /* thread handler, will be assigned in fix_fields only */
   THD *thd;
-  /* prepared statement, or 0 */
-  Statement *stmt;
   /* substitution instead of subselect in case of optimization */
   Item *substitution;
   /* unit of subquery */

sql/item_sum.cc

@@ -64,28 +64,28 @@ Item_sum::Item_sum(THD *thd, Item_sum *item):
 
 
 /*
-  Save copy of arguments if we are prepare prepared statement
+  Save copy of arguments if we prepare prepared statement
   (arguments can be rewritten in get_tmp_table_item())
 
   SYNOPSIS
-    Item_sum::save_args_for_prepared_statements()
+    Item_sum::save_args_for_prepared_statement()
     thd		- thread handler
 
   RETURN
     0 - OK
     1 - Error
 */
-bool Item_sum::save_args_for_prepared_statements(THD *thd)
+bool Item_sum::save_args_for_prepared_statement(THD *thd)
 {
-  if (thd->current_statement)
-    return save_args(thd->current_statement);
+  if (thd->current_arena->is_stmt_prepare())
+    return save_args(thd->current_arena);
   return 0;
 }
 
 
-bool Item_sum::save_args(Statement* stmt)
+bool Item_sum::save_args(Item_arena* arena)
 {
-  if (!(args_copy= (Item**) stmt->alloc(sizeof(Item*)*arg_count)))
+  if (!(args_copy= (Item**) arena->alloc(sizeof(Item*)*arg_count)))
     return 1;
   memcpy(args_copy, args, sizeof(Item*)*arg_count);
   return 0;
@@ -214,7 +214,7 @@ Item_sum_num::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
 {
   DBUG_ASSERT(fixed == 0);
 
-  if (save_args_for_prepared_statements(thd))
+  if (save_args_for_prepared_statement(thd))
     return 1;
   
   if (!thd->allow_sum_func)
@@ -248,7 +248,7 @@ Item_sum_hybrid::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
 {
   DBUG_ASSERT(fixed == 0);
 
-  if (save_args_for_prepared_statements(thd))
+  if (save_args_for_prepared_statement(thd))
     return 1;
 
   Item *item= args[0];
@@ -1947,7 +1947,7 @@ Item_func_group_concat::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
 {
   DBUG_ASSERT(fixed == 0);
 
-  if (save_args_for_prepared_statements(thd))
+  if (save_args_for_prepared_statement(thd))
     return 1;
 
   uint i;			/* for loop variable */ 

sql/item_sum.h

@@ -92,8 +92,8 @@ class Item_sum :public Item_result_field
   virtual bool setup(THD *thd) {return 0;}
   virtual void make_unique() {}
   Item *get_tmp_table_item(THD *thd);
-  bool save_args_for_prepared_statements(THD *);
-  bool save_args(Statement* stmt);
+  bool save_args_for_prepared_statement(THD *);
+  bool save_args(Item_arena *arena);
 
   bool walk (Item_processor processor, byte *argument);
 };

sql/mysql_priv.h

@@ -295,7 +295,7 @@ void debug_sync_point(const char* lock_name, uint lock_timeout);
 
 struct st_table;
 class THD;
-class Statement;
+class Item_arena;
 
 /* Struct to handle simple linked lists */
 

sql/sql_base.cc

@@ -2188,14 +2188,15 @@ int setup_wild(THD *thd, TABLE_LIST *tables, List<Item> &fields,
 {
   if (!wild_num)
     return 0;
-  Statement *stmt= thd->current_statement, backup;
+  Item_arena *arena= thd->current_arena, backup;
 
   /*
     If we are in preparing prepared statement phase then we have change
     temporary mem_root to statement mem root to save changes of SELECT list
   */
-  if (stmt)
-    thd->set_n_backup_item_arena(stmt, &backup);
+  if (arena->is_stmt_prepare())
+    thd->set_n_backup_item_arena(arena, &backup);
+
   reg2 Item *item;
   List_iterator<Item> it(fields);
   while ( wild_num && (item= it++))
@@ -2219,8 +2220,8 @@ int setup_wild(THD *thd, TABLE_LIST *tables, List<Item> &fields,
       else if (insert_fields(thd,tables,((Item_field*) item)->db_name,
                              ((Item_field*) item)->table_name, &it))
       {
-	if (stmt)
-	  thd->restore_backup_item_arena(stmt, &backup);
+        if (arena->is_stmt_prepare())
+	  thd->restore_backup_item_arena(arena, &backup);
 	return (-1);
       }
       if (sum_func_list)
@@ -2235,8 +2236,8 @@ int setup_wild(THD *thd, TABLE_LIST *tables, List<Item> &fields,
       wild_num--;
     }
   }
-  if (stmt)
-      thd->restore_backup_item_arena(stmt, &backup);
+  if (arena->is_stmt_prepare())
+      thd->restore_backup_item_arena(arena, &backup);
   return 0;
 }
 
@@ -2449,7 +2450,7 @@ insert_fields(THD *thd,TABLE_LIST *tables, const char *db_name,
 int setup_conds(THD *thd,TABLE_LIST *tables,COND **conds)
 {
   table_map not_null_tables= 0;
-  Statement *stmt= thd->current_statement, backup;
+  Item_arena *arena= thd->current_arena, backup;
 
   DBUG_ENTER("setup_conds");
   thd->set_query_id=1;
@@ -2488,12 +2489,12 @@ int setup_conds(THD *thd,TABLE_LIST *tables,COND **conds)
 	   !(specialflag & SPECIAL_NO_NEW_FUNC)))
       {
 	table->outer_join= 0;
-	if (stmt)
-	  thd->set_n_backup_item_arena(stmt, &backup);
+	if (arena->is_stmt_prepare())
+	  thd->set_n_backup_item_arena(arena, &backup);
 	*conds= and_conds(*conds, table->on_expr);
 	table->on_expr=0;
-	if (stmt)
-	  thd->restore_backup_item_arena(stmt, &backup);
+	if (arena->is_stmt_prepare())
+	  thd->restore_backup_item_arena(arena, &backup);
 	if ((*conds) && !(*conds)->fixed &&
 	    (*conds)->fix_fields(thd, tables, conds))
 	  DBUG_RETURN(1);
@@ -2501,8 +2502,8 @@ int setup_conds(THD *thd,TABLE_LIST *tables,COND **conds)
     }
     if (table->natural_join)
     {
-      if (stmt)
-	thd->set_n_backup_item_arena(stmt, &backup);
+      if (arena->is_stmt_prepare())
+	thd->set_n_backup_item_arena(arena, &backup);
       /* Make a join of all fields with have the same name */
       TABLE *t1= table->table;
       TABLE *t2= table->natural_join->table;
@@ -2543,8 +2544,8 @@ int setup_conds(THD *thd,TABLE_LIST *tables,COND **conds)
         {
           *conds= and_conds(*conds, cond_and);
           // fix_fields() should be made with temporary memory pool
-          if (stmt)
-            thd->restore_backup_item_arena(stmt, &backup);
+          if (arena->is_stmt_prepare())
+            thd->restore_backup_item_arena(arena, &backup);
           if (*conds && !(*conds)->fixed)
           {
             if ((*conds)->fix_fields(thd, tables, conds))
@@ -2555,8 +2556,8 @@ int setup_conds(THD *thd,TABLE_LIST *tables,COND **conds)
         {
           table->on_expr= and_conds(table->on_expr, cond_and);
           // fix_fields() should be made with temporary memory pool
-          if (stmt)
-            thd->restore_backup_item_arena(stmt, &backup);
+          if (arena->is_stmt_prepare())
+            thd->restore_backup_item_arena(arena, &backup);
           if (table->on_expr && !table->on_expr->fixed)
           {
             if (table->on_expr->fix_fields(thd, tables, &table->on_expr))
@@ -2567,7 +2568,7 @@ int setup_conds(THD *thd,TABLE_LIST *tables,COND **conds)
     }
   }
 
-  if (stmt)
+  if (arena->is_stmt_prepare())
   {
     /*
       We are in prepared statement preparation code => we should store
@@ -2580,8 +2581,8 @@ int setup_conds(THD *thd,TABLE_LIST *tables,COND **conds)
   DBUG_RETURN(test(thd->net.report_error));
 
 err:
-  if (stmt)
-      thd->restore_backup_item_arena(stmt, &backup);
+  if (arena->is_stmt_prepare())
+      thd->restore_backup_item_arena(arena, &backup);
   DBUG_RETURN(1);
 }
 

sql/sql_class.cc

@@ -155,7 +155,7 @@ bool foreign_key_prefix(Key *a, Key *b)
 ** Thread specific functions
 ****************************************************************************/
 
-THD::THD():user_time(0), current_statement(0), is_fatal_error(0),
+THD::THD():user_time(0), current_arena(this), is_fatal_error(0),
 	   last_insert_id_used(0),
            insert_id_used(0), rand_used(0), time_zone_used(0),
            in_lock_tables(0), global_read_lock(0), bootstrap(0)
@@ -1301,23 +1301,59 @@ int select_dumpvar::prepare(List<Item> &list, SELECT_LEX_UNIT *u)
 }
 
 
+Item_arena::Item_arena(THD* thd)
+  :free_list(0),
+  state(INITIALIZED)
+{
+  init_sql_alloc(&mem_root,
+                 thd->variables.query_alloc_block_size,
+                 thd->variables.query_prealloc_size);
+}
+
+
+/* This constructor is called when Item_arena is a subobject of THD */
+
+Item_arena::Item_arena()
+  :free_list(0),
+  state(CONVENTIONAL_EXECUTION)
+{
+  clear_alloc_root(&mem_root);
+}
+
+
+Item_arena::Item_arena(bool init_mem_root)
+  :free_list(0),
+  state(INITIALIZED)
+{
+  if (init_mem_root)
+    clear_alloc_root(&mem_root);
+}
+
+Item_arena::Type Item_arena::type() const
+{
+  DBUG_ASSERT("Item_arena::type()" == "abstract");
+  return STATEMENT;
+}
+
+
+Item_arena::~Item_arena()
+{}
+
+
 /*
   Statement functions 
 */
 
 Statement::Statement(THD *thd)
-  :id(++thd->statement_id_counter),
+  :Item_arena(thd),
+  id(++thd->statement_id_counter),
   set_query_id(1),
   allow_sum_func(0),
   lex(&main_lex),
   query(0),
-  query_length(0),
-  free_list(0)
+  query_length(0)
 {
   name.str= NULL;
-  init_sql_alloc(&mem_root,
-                 thd->variables.query_alloc_block_size,
-                 thd->variables.query_prealloc_size);
 }
 
 /*
@@ -1332,14 +1368,12 @@ Statement::Statement()
   allow_sum_func(0),                            /* initialized later */
   lex(&main_lex),
   query(0),                                     /* these two are set */ 
-  query_length(0),                              /* in alloc_query() */
-  free_list(0)
+  query_length(0)                               /* in alloc_query() */
 {
-  bzero((char *) &mem_root, sizeof(mem_root));
 }
 
 
-Statement::Type Statement::type() const
+Item_arena::Type Statement::type() const
 {
   return STATEMENT;
 }
@@ -1356,14 +1390,29 @@ void Statement::set_statement(Statement *stmt)
 }
 
 
-void Statement::set_n_backup_item_arena(Statement *set, Statement *backup)
+void
+Statement::set_n_backup_statement(Statement *stmt, Statement *backup)
+{
+  backup->set_statement(this);
+  set_statement(stmt);
+}
+
+
+void Statement::restore_backup_statement(Statement *stmt, Statement *backup)
+{
+  stmt->set_statement(this);
+  set_statement(backup);
+}
+
+
+void Item_arena::set_n_backup_item_arena(Item_arena *set, Item_arena *backup)
 {
   backup->set_item_arena(this);
   set_item_arena(set);
 }
 
 
-void Statement::restore_backup_item_arena(Statement *set, Statement *backup)
+void Item_arena::restore_backup_item_arena(Item_arena *set, Item_arena *backup)
 {
   set->set_item_arena(this);
   set_item_arena(backup);
@@ -1371,10 +1420,11 @@ void Statement::restore_backup_item_arena(Statement *set, Statement *backup)
   init_alloc_root(&backup->mem_root, 0, 0);
 }
 
-void Statement::set_item_arena(Statement *set)
+void Item_arena::set_item_arena(Item_arena *set)
 {
   mem_root= set->mem_root;
   free_list= set->free_list;
+  state= set->state;
 }
 
 Statement::~Statement()

sql/sql_class.h

@@ -418,6 +418,61 @@ struct system_variables
 void free_tmp_table(THD *thd, TABLE *entry);
 
 
+class Item_arena
+{
+public:
+  /*
+    List of items created in the parser for this query. Every item puts
+    itself to the list on creation (see Item::Item() for details))
+  */
+  Item *free_list;
+  MEM_ROOT mem_root;
+  static const int INITIALIZED= 0, PREPARED= 1, EXECUTED= 3,
+                   CONVENTIONAL_EXECUTION= 2, ERROR= -1;
+  int state;
+
+  /* We build without RTTI, so dynamic_cast can't be used. */
+  enum Type
+  {
+    STATEMENT, PREPARED_STATEMENT, STORED_PROCEDURE
+  };
+
+  Item_arena(THD *thd);
+  Item_arena();
+  Item_arena(bool init_mem_root);
+  virtual Type type() const;
+  virtual ~Item_arena();
+
+  inline bool is_stmt_prepare() const { return state < PREPARED; }
+  inline bool is_first_stmt_execute() const { return state == PREPARED; }
+  inline gptr alloc(unsigned int size) { return alloc_root(&mem_root,size); }
+  inline gptr calloc(unsigned int size)
+  {
+    gptr ptr;
+    if ((ptr=alloc_root(&mem_root,size)))
+      bzero((char*) ptr,size);
+    return ptr;
+  }
+  inline char *strdup(const char *str)
+  { return strdup_root(&mem_root,str); }
+  inline char *strmake(const char *str, uint size)
+  { return strmake_root(&mem_root,str,size); }
+  inline char *memdup(const char *str, uint size)
+  { return memdup_root(&mem_root,str,size); }
+  inline char *memdup_w_gap(const char *str, uint size, uint gap)
+  {
+    gptr ptr;
+    if ((ptr=alloc_root(&mem_root,size+gap)))
+      memcpy(ptr,str,size);
+    return ptr;
+  }
+
+  void set_n_backup_item_arena(Item_arena *set, Item_arena *backup);
+  void restore_backup_item_arena(Item_arena *set, Item_arena *backup);
+  void set_item_arena(Item_arena *set);
+};
+
+
 /*
   State of a single command executed against this connection.
   One connection can contain a lot of simultaneously running statements,
@@ -432,7 +487,7 @@ void free_tmp_table(THD *thd, TABLE *entry);
   be used explicitly.
 */
 
-class Statement
+class Statement: public Item_arena
 {
   Statement(const Statement &rhs);              /* not implemented: */
   Statement &operator=(const Statement &rhs);   /* non-copyable */
@@ -474,20 +529,8 @@ class Statement
   */
   char *query;
   uint32 query_length;                          // current query length
-  /*
-    List of items created in the parser for this query. Every item puts
-    itself to the list on creation (see Item::Item() for details))
-  */
-  Item *free_list;
-  MEM_ROOT mem_root;
 
 public:
-  /* We build without RTTI, so dynamic_cast can't be used. */
-  enum Type
-  {
-    STATEMENT,
-    PREPARED_STATEMENT
-  };
 
   /*
     This constructor is called when statement is a subobject of THD:
@@ -500,34 +543,10 @@ class Statement
 
   /* Assign execution context (note: not all members) of given stmt to self */
   void set_statement(Statement *stmt);
+  void set_n_backup_statement(Statement *stmt, Statement *backup);
+  void restore_backup_statement(Statement *stmt, Statement *backup);
   /* return class type */
   virtual Type type() const;
-
-  inline gptr alloc(unsigned int size) { return alloc_root(&mem_root,size); }
-  inline gptr calloc(unsigned int size)
-  {
-    gptr ptr;
-    if ((ptr=alloc_root(&mem_root,size)))
-      bzero((char*) ptr,size);
-    return ptr;
-  }
-  inline char *strdup(const char *str)
-  { return strdup_root(&mem_root,str); }
-  inline char *strmake(const char *str, uint size)
-  { return strmake_root(&mem_root,str,size); }
-  inline char *memdup(const char *str, uint size)
-  { return memdup_root(&mem_root,str,size); }
-  inline char *memdup_w_gap(const char *str, uint size, uint gap)
-  {
-    gptr ptr;
-    if ((ptr=alloc_root(&mem_root,size+gap)))
-      memcpy(ptr,str,size);
-    return ptr;
-  }
-
-  void set_n_backup_item_arena(Statement *set, Statement *backup);
-  void restore_backup_item_arena(Statement *set, Statement *backup);
-  void set_item_arena(Statement *set);
 };
 
 
@@ -760,9 +779,9 @@ class THD :public ilink,
   Vio* active_vio;
 #endif
   /*
-    Current prepared Statement if there one, or 0
+    Current prepared Item_arena if there one, or 0
   */
-  Statement *current_statement;
+  Item_arena *current_arena;
   /*
     next_insert_id is set on SET INSERT_ID= #. This is used as the next
     generated auto_increment value in handler.cc
@@ -983,33 +1002,6 @@ class THD :public ilink,
   }
   inline CHARSET_INFO *charset() { return variables.character_set_client; }
   void update_charset();
-
-  inline void allocate_temporary_memory_pool_for_ps_preparing()
-  {
-    DBUG_ASSERT(current_statement!=0);
-    /*
-      We do not want to have in PS memory all that junk,
-      which will be created by preparation => substitute memory
-      from original thread pool.
-
-      We know that PS memory pool is now copied to THD, we move it back
-      to allow some code use it.
-    */
-    current_statement->set_item_arena(this);
-    init_sql_alloc(&mem_root,
-		   variables.query_alloc_block_size,
-		   variables.query_prealloc_size);
-    free_list= 0;
-  }
-  inline void free_temporary_memory_pool_for_ps_preparing()
-  {
-    DBUG_ASSERT(current_statement!=0);
-    cleanup_items(current_statement->free_list);
-    free_items(free_list);
-    close_thread_tables(this); // to close derived tables
-    free_root(&mem_root, MYF(0));
-    set_item_arena(current_statement);
-  }
 };
 
 /* Flags for the THD::system_thread (bitmap) variable */

sql/sql_derived.cc

@@ -151,7 +151,7 @@ static int mysql_derived(THD *thd, LEX *lex, SELECT_LEX_UNIT *unit,
     if it is preparation PS only then we do not need real data and we
     can skip execution (and parameters is not defined, too)
   */
-  if (!thd->current_statement)
+  if (! thd->current_arena->is_stmt_prepare())
   {
     if (is_union)
     {

sql/sql_lex.cc

@@ -1527,9 +1527,9 @@ bool st_select_lex::setup_ref_array(THD *thd, uint order_group_num)
     We have to create array in prepared statement memory if it is
     prepared statement
   */
-  Statement *stmt= thd->current_statement ? thd->current_statement : thd;
+  Item_arena *arena= thd->current_arena;
   return (ref_pointer_array= 
-	  (Item **)stmt->alloc(sizeof(Item*) *
+	  (Item **)arena->alloc(sizeof(Item*) *
 			       (item_list.elements +
 				select_n_having_items +
 				order_group_num)* 5)) == 0;

sql/sql_parse.cc

@@ -1543,6 +1543,7 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
       break;
     mysqld_list_fields(thd,&table_list,fields);
     free_items(thd->free_list);
+    thd->free_list= 0;
     break;
   }
 #endif
@@ -4047,6 +4048,7 @@ void mysql_parse(THD *thd, char *inBuf, uint length)
     }
     thd->proc_info="freeing items";
     free_items(thd->free_list);  /* Free strings used by items */
+    thd->free_list= 0;
     lex_end(lex);
   }
   DBUG_VOID_RETURN;
@@ -4073,6 +4075,7 @@ bool mysql_test_parse_for_slave(THD *thd, char *inBuf, uint length)
       all_tables_not_ok(thd,(TABLE_LIST*) lex->select_lex.table_list.first))
     error= 1;                /* Ignore question */
   free_items(thd->free_list);  /* Free strings used by items */
+  thd->free_list= 0;
   lex_end(lex);
 
   return error;

sql/sql_select.cc

@@ -4377,25 +4377,39 @@ COND *eliminate_not_funcs(THD *thd, COND *cond)
 static COND *
 optimize_cond(THD *thd, COND *conds, Item::cond_result *cond_value)
 {
+  SELECT_LEX *select= thd->lex->current_select;
   DBUG_ENTER("optimize_cond");
-  if (!conds)
+  if (conds)
+  {
+    DBUG_EXECUTE("where", print_where(conds, "original"););
+    /* Eliminate NOT operators; in case of PS/SP do it once */
+    if (thd->current_arena->is_first_stmt_execute())
+    {
+      Item_arena *arena= thd->current_arena, backup;
+      thd->set_n_backup_item_arena(arena, &backup);
+      conds= eliminate_not_funcs(thd, conds);
+      select->prep_where= conds->copy_andor_structure(thd);
+      thd->restore_backup_item_arena(arena, &backup);
+    }
+    else
+      conds= eliminate_not_funcs(thd, conds);
+    DBUG_EXECUTE("where", print_where(conds, "after negation elimination"););
+
+    /* change field = field to field = const for each found field = const */
+    propagate_cond_constants((I_List<COND_CMP> *) 0, conds, conds);
+    /*
+      Remove all instances of item == item
+      Remove all and-levels where CONST item != CONST item
+    */
+    DBUG_EXECUTE("where", print_where(conds, "after const change"););
+    conds= remove_eq_conds(thd, conds, cond_value);
+    DBUG_EXECUTE("info", print_where(conds, "after remove"););
+  }
+  else
   {
     *cond_value= Item::COND_TRUE;
-    DBUG_RETURN(conds);
-  }
-  DBUG_EXECUTE("where",print_where(conds,"original"););
-  /* eliminate NOT operators */
-  conds= eliminate_not_funcs(thd, conds);
-  DBUG_EXECUTE("where", print_where(conds, "after negation elimination"););
-  /* change field = field to field = const for each found field = const */
-  propagate_cond_constants((I_List<COND_CMP> *) 0,conds,conds);
-  /*
-    Remove all instances of item == item
-    Remove all and-levels where CONST item != CONST item
-  */
-  DBUG_EXECUTE("where",print_where(conds,"after const change"););
-  conds= remove_eq_conds(thd, conds, cond_value) ;
-  DBUG_EXECUTE("info",print_where(conds,"after remove"););
+    select->prep_where= 0;
+  }
   DBUG_RETURN(conds);
 }
 

sql/sql_union.cc

@@ -287,24 +287,23 @@ int st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
     thd_arg->lex->current_select= lex_select_save;
     if (!item_list.elements)
     {
-      Statement *stmt= thd->current_statement;
-      Statement backup;
-      if (stmt)
-	thd->set_n_backup_item_arena(stmt, &backup);
+      Item_arena *arena= thd->current_arena, backup;
+      if (arena->is_stmt_prepare())
+	thd->set_n_backup_item_arena(arena, &backup);
       Field **field;
       for (field= table->field; *field; field++)
       {
 	Item_field *item= new Item_field(*field);
 	if (!item || item_list.push_back(item))
 	{
-	  if (stmt)
-	    thd->restore_backup_item_arena(stmt, &backup);
+          if (arena->is_stmt_prepare())
+	    thd->restore_backup_item_arena(arena, &backup);
 	  DBUG_RETURN(-1);
 	}
       }
-      if (stmt)
+      if (arena->is_stmt_prepare())
       {
-	thd->restore_backup_item_arena(stmt, &backup);
+	thd->restore_backup_item_arena(arena, &backup);
 
 	/* prepare fake select to initialize it correctly */
 	ulong options_tmp= init_prepare_fake_select_lex(thd);