Fixed LP bug #794901.

Also:
1. simplified the code of the function mysql_derived_merge_for_insert.
2. moved merge of views/dt for multi-update/delete to the prepare stage.
3. the list of the references to the candidates for semi-join now is
   allocated in the statement memory.

11 files changed, 123 insertions, 137 deletions

diff --git a/sql/item_subselect.cc b/sql/item_subselect.cc
index f7c778dbdbf..8679a4f9a0d 100644
--- a/sql/item_subselect.cc
+++ b/sql/item_subselect.cc
@@ -1146,7 +1146,8 @@ Item_in_subselect::Item_in_subselect(Item * left_exp,
 				     st_select_lex *select_lex):
   Item_exists_subselect(), left_expr_cache(0), first_execution(TRUE),
   optimizer(0), pushed_cond_guards(NULL), in_strategy(0),
-  is_jtbm_merged(FALSE), is_flattenable_semijoin(FALSE), 
+  is_jtbm_merged(FALSE), is_flattenable_semijoin(FALSE),
+  is_registered_semijoin(FALSE), 
   upper_item(0)
 {
   DBUG_ENTER("Item_in_subselect::Item_in_subselect");
diff --git a/sql/item_subselect.h b/sql/item_subselect.h
index 26a45a14dbe..02239ad77d3 100644
--- a/sql/item_subselect.h
+++ b/sql/item_subselect.h
@@ -459,6 +459,11 @@ public:
   bool is_flattenable_semijoin;
 
   /*
+    TRUE<=>registered in the list of semijoins in outer select
+  */
+  bool is_registered_semijoin;
+
+  /*
     Used to determine how this subselect item is represented in the item tree,
     in case there is a need to locate it there and replace with something else.
     Two options are possible:
diff --git a/sql/opt_subselect.cc b/sql/opt_subselect.cc
index bd07bb63ceb..5d97d016499 100644
--- a/sql/opt_subselect.cc
+++ b/sql/opt_subselect.cc
@@ -177,8 +177,8 @@ bool subquery_types_allow_materialization(Item_in_subselect *in_subs);
 static bool replace_where_subcondition(JOIN *join, Item **expr, 
                                        Item *old_cond, Item *new_cond,
                                        bool do_fix_fields);
-static int subq_sj_candidate_cmp(Item_in_subselect* const *el1, 
-                                 Item_in_subselect* const *el2);
+static int subq_sj_candidate_cmp(Item_in_subselect* el1, Item_in_subselect* el2,
+                                 void *arg);
 static bool convert_subq_to_sj(JOIN *parent_join, Item_in_subselect *subq_pred);
 static bool convert_subq_to_jtbm(JOIN *parent_join, 
                                  Item_in_subselect *subq_pred, bool *remove);
@@ -357,8 +357,15 @@ int check_and_do_in_subquery_rewrites(JOIN *join)
       in_subs->is_flattenable_semijoin= TRUE;
 
       /* Register the subquery for further processing in flatten_subqueries() */
-      select_lex->
-        outer_select()->join->sj_subselects.append(thd->mem_root, in_subs);
+      if (!in_subs->is_registered_semijoin)
+      {
+        Query_arena *arena, backup;
+        arena= thd->activate_stmt_arena_if_needed(&backup);
+        select_lex->outer_select()->sj_subselects.push_back(in_subs);
+        if (arena)
+          thd->restore_active_arena(arena, &backup);
+        in_subs->is_registered_semijoin= TRUE;
+      }
     }
     else
     {
@@ -405,7 +412,7 @@ int check_and_do_in_subquery_rewrites(JOIN *join)
                condition also excludes multi-table update statements.
         A note about prepared statements: we want the if-branch to be taken on
         PREPARE and each EXECUTE. The rewrites are only done once, but we need 
-        join->sj_subselects list to be populated for every EXECUTE. 
+        select_lex->sj_subselects list to be populated for every EXECUTE. 
 
         */
         if (optimizer_flag(thd, OPTIMIZER_SWITCH_MATERIALIZATION) &&      // 0
@@ -432,8 +439,15 @@ int check_and_do_in_subquery_rewrites(JOIN *join)
           {
             in_subs->emb_on_expr_nest= thd->thd_marker.emb_on_expr_nest;
             in_subs->is_flattenable_semijoin= FALSE;
-            select_lex->outer_select()->
-              join->sj_subselects.append(thd->mem_root, in_subs);
+            if (!in_subs->is_registered_semijoin)
+	    {
+              Query_arena *arena, backup;
+              arena= thd->activate_stmt_arena_if_needed(&backup);
+              select_lex->outer_select()->sj_subselects.push_back(in_subs);
+              if (arena)
+                thd->restore_active_arena(arena, &backup);
+              in_subs->is_registered_semijoin= TRUE;
+            }
           }
         }
 
@@ -731,21 +745,19 @@ bool check_for_outer_joins(List<TABLE_LIST> *join_list)
 bool convert_join_subqueries_to_semijoins(JOIN *join)
 {
   Query_arena *arena, backup;
-  Item_in_subselect **in_subq;
-  Item_in_subselect **in_subq_end;
+  Item_in_subselect *in_subq;
   THD *thd= join->thd;
   List_iterator<TABLE_LIST> ti(join->select_lex->leaf_tables);
   DBUG_ENTER("convert_join_subqueries_to_semijoins");
 
-  if (join->sj_subselects.elements() == 0)
+  if (join->select_lex->sj_subselects.is_empty())
     DBUG_RETURN(FALSE);
 
-  for (in_subq= join->sj_subselects.front(), 
-       in_subq_end= join->sj_subselects.back(); 
-       in_subq != in_subq_end; 
-       in_subq++)
+  List_iterator_fast<Item_in_subselect> li(join->select_lex->sj_subselects);
+
+  while ((in_subq= li++))
   {
-    SELECT_LEX *subq_sel= (*in_subq)->get_select_lex();
+    SELECT_LEX *subq_sel= in_subq->get_select_lex();
     if (subq_sel->handle_derived(thd->lex, DT_OPTIMIZE))
       DBUG_RETURN(1);
     if (subq_sel->handle_derived(thd->lex, DT_MERGE))
@@ -753,13 +765,11 @@ bool convert_join_subqueries_to_semijoins(JOIN *join)
     subq_sel->update_used_tables();
   }
 
+  li.rewind();
   /* First, convert child join's subqueries. We proceed bottom-up here */
-  for (in_subq= join->sj_subselects.front(), 
-       in_subq_end= join->sj_subselects.back(); 
-       in_subq != in_subq_end; 
-       in_subq++)
+  while ((in_subq= li++)) 
   {
-    st_select_lex *child_select= (*in_subq)->get_select_lex();
+    st_select_lex *child_select= in_subq->get_select_lex();
     JOIN *child_join= child_select->join;
     child_join->outer_tables = child_join->table_count;
 
@@ -773,9 +783,9 @@ bool convert_join_subqueries_to_semijoins(JOIN *join)
 
     if (convert_join_subqueries_to_semijoins(child_join))
       DBUG_RETURN(TRUE);
-    (*in_subq)->sj_convert_priority= 
-      test((*in_subq)->emb_on_expr_nest != NO_JOIN_NEST) * MAX_TABLES * 2 +
-      (*in_subq)->is_correlated * MAX_TABLES + child_join->outer_tables;
+    in_subq->sj_convert_priority= 
+      test(in_subq->emb_on_expr_nest != NO_JOIN_NEST) * MAX_TABLES * 2 +
+      in_subq->is_correlated * MAX_TABLES + child_join->outer_tables;
   }
   
   // Temporary measure: disable semi-joins when they are together with outer
@@ -783,7 +793,7 @@ bool convert_join_subqueries_to_semijoins(JOIN *join)
 #if 0  
   if (check_for_outer_joins(join->join_list))
   {
-    in_subq= join->sj_subselects.front();
+    in_subq= join->select_lex->sj_subselects.head();
     arena= thd->activate_stmt_arena_if_needed(&backup);
     goto skip_conversion;
   }
@@ -795,41 +805,41 @@ bool convert_join_subqueries_to_semijoins(JOIN *join)
       - prefer correlated subqueries over uncorrelated;
       - prefer subqueries that have greater number of outer tables;
   */
-  join->sj_subselects.sort(subq_sj_candidate_cmp);
+  bubble_sort<Item_in_subselect>(&join->select_lex->sj_subselects,
+				 subq_sj_candidate_cmp, NULL);
   // #tables-in-parent-query + #tables-in-subquery < MAX_TABLES
   /* Replace all subqueries to be flattened with Item_int(1) */
   arena= thd->activate_stmt_arena_if_needed(&backup);
  
-  for (in_subq= join->sj_subselects.front(); 
-       in_subq != in_subq_end;
-       in_subq++)
+  li.rewind();
+  while ((in_subq= li++))
   {
     bool remove_item= TRUE;
 
     /* Stop processing if we've reached a subquery that's attached to the ON clause */
-    if ((*in_subq)->emb_on_expr_nest != NO_JOIN_NEST)
+    if (in_subq->emb_on_expr_nest != NO_JOIN_NEST)
       break;
 
-    if ((*in_subq)->is_flattenable_semijoin) 
+    if (in_subq->is_flattenable_semijoin) 
     {
       if (join->table_count + 
-          (*in_subq)->unit->first_select()->join->table_count >= MAX_TABLES)
+          in_subq->unit->first_select()->join->table_count >= MAX_TABLES)
         break;
-      if (convert_subq_to_sj(join, *in_subq))
+      if (convert_subq_to_sj(join, in_subq))
         DBUG_RETURN(TRUE);
     }
     else
     {
       if (join->table_count + 1 >= MAX_TABLES)
         break;
-      if (convert_subq_to_jtbm(join, *in_subq, &remove_item))
+      if (convert_subq_to_jtbm(join, in_subq, &remove_item))
         DBUG_RETURN(TRUE);
     }
     if (remove_item)
     {
-      Item **tree= ((*in_subq)->emb_on_expr_nest == NO_JOIN_NEST)?
-                     &join->conds : &((*in_subq)->emb_on_expr_nest->on_expr);
-      Item *replace_me= (*in_subq)->original_item();
+      Item **tree= (in_subq->emb_on_expr_nest == NO_JOIN_NEST)?
+                     &join->conds : &(in_subq->emb_on_expr_nest->on_expr);
+      Item *replace_me= in_subq->original_item();
       if (replace_where_subcondition(join, tree, replace_me, new Item_int(1),
                                      FALSE))
         DBUG_RETURN(TRUE); /* purecov: inspected */
@@ -840,34 +850,34 @@ bool convert_join_subqueries_to_semijoins(JOIN *join)
     3. Finalize (perform IN->EXISTS rewrite) the subqueries that we didn't
     convert:
   */
-  for (; in_subq!= in_subq_end; in_subq++)
+  while (in_subq)
   {
-    JOIN *child_join= (*in_subq)->unit->first_select()->join;
-    (*in_subq)->changed= 0;
-    (*in_subq)->fixed= 0;
+    JOIN *child_join= in_subq->unit->first_select()->join;
+    in_subq->changed= 0;
+    in_subq->fixed= 0;
 
     SELECT_LEX *save_select_lex= thd->lex->current_select;
-    thd->lex->current_select= (*in_subq)->unit->first_select();
+    thd->lex->current_select= in_subq->unit->first_select();
 
-    bool res= (*in_subq)->select_transformer(child_join);
+    bool res= in_subq->select_transformer(child_join);
 
     thd->lex->current_select= save_select_lex;
 
     if (res)
       DBUG_RETURN(TRUE);
 
-    (*in_subq)->changed= 1;
-    (*in_subq)->fixed= 1;
+    in_subq->changed= 1;
+    in_subq->fixed= 1;
 
-    Item *substitute= (*in_subq)->substitution;
-    bool do_fix_fields= !(*in_subq)->substitution->fixed;
-    Item **tree= ((*in_subq)->emb_on_expr_nest == NO_JOIN_NEST)?
-                   &join->conds : &((*in_subq)->emb_on_expr_nest->on_expr);
-    Item *replace_me= (*in_subq)->original_item();
+    Item *substitute= in_subq->substitution;
+    bool do_fix_fields= !in_subq->substitution->fixed;
+    Item **tree= (in_subq->emb_on_expr_nest == NO_JOIN_NEST)?
+                   &join->conds : &(in_subq->emb_on_expr_nest->on_expr);
+    Item *replace_me= in_subq->original_item();
     if (replace_where_subcondition(join, tree, replace_me, substitute, 
                                    do_fix_fields))
       DBUG_RETURN(TRUE);
-    (*in_subq)->substitution= NULL;
+    in_subq->substitution= NULL;
 #if 0
     /* 
       Don't do the following, because the simplify_join() call is after this
@@ -881,9 +891,9 @@ bool convert_join_subqueries_to_semijoins(JOIN *join)
     */
     if (!thd->stmt_arena->is_conventional())
     {
-      tree= ((*in_subq)->emb_on_expr_nest == NO_JOIN_NEST)?
+      tree= (in_subq->emb_on_expr_nest == NO_JOIN_NEST)?
              &join->select_lex->prep_where : 
-             &((*in_subq)->emb_on_expr_nest->prep_on_expr);
+             &(in_subq->emb_on_expr_nest->prep_on_expr);
 
       if (replace_where_subcondition(join, tree, replace_me, substitute, 
                                      FALSE))
@@ -898,12 +908,13 @@ bool convert_join_subqueries_to_semijoins(JOIN *join)
       re-run the test for materialization that was done in
       check_and_do_in_subquery_rewrites.
     */
-    (*in_subq)->in_strategy= SUBS_IN_TO_EXISTS;
+    in_subq->in_strategy= SUBS_IN_TO_EXISTS;
+    in_subq= li++;
   }
 
   if (arena)
     thd->restore_active_arena(arena, &backup);
-  join->sj_subselects.clear();
+  join->select_lex->sj_subselects.empty();
   DBUG_RETURN(FALSE);
 }
 
@@ -1004,11 +1015,11 @@ static bool replace_where_subcondition(JOIN *join, Item **expr,
   return TRUE;
 }
 
-static int subq_sj_candidate_cmp(Item_in_subselect* const *el1, 
-                                 Item_in_subselect* const *el2)
+static int subq_sj_candidate_cmp(Item_in_subselect* el1, Item_in_subselect* el2,
+                                 void *arg)
 {
-  return ((*el1)->sj_convert_priority < (*el2)->sj_convert_priority) ? 1 : 
-         ( ((*el1)->sj_convert_priority == (*el2)->sj_convert_priority)? 0 : -1);
+  return (el1->sj_convert_priority > el2->sj_convert_priority) ? 1 : 
+         ( (el1->sj_convert_priority == el2->sj_convert_priority)? 0 : -1);
 }
 
 
diff --git a/sql/sql_delete.cc b/sql/sql_delete.cc
index 7f3ed2e705f..becc1ada7ae 100644
--- a/sql/sql_delete.cc
+++ b/sql/sql_delete.cc
@@ -603,9 +603,11 @@ int mysql_multi_delete_prepare(THD *thd)
                                     &thd->lex->select_lex.top_join_list,
                                     lex->query_tables,
                                     lex->select_lex.leaf_tables, FALSE, 
-                                    DELETE_ACL, SELECT_ACL, TRUE))
+                                    DELETE_ACL, SELECT_ACL, FALSE))
     DBUG_RETURN(TRUE);
 
+  if (lex->select_lex.handle_derived(thd->lex, DT_MERGE))  
+    DBUG_RETURN(TRUE);
 
   /*
     Multi-delete can't be constructed over-union => we always have
diff --git a/sql/sql_derived.cc b/sql/sql_derived.cc
index 0f860986bab..e3de7d9c2dd 100644
--- a/sql/sql_derived.cc
+++ b/sql/sql_derived.cc
@@ -346,10 +346,17 @@ bool mysql_derived_merge(THD *thd, LEX *lex, TABLE_LIST *derived)
   if (derived->merged)
     return FALSE;
 
+ if (thd->lex->sql_command == SQLCOM_UPDATE_MULTI ||
+     thd->lex->sql_command == SQLCOM_DELETE_MULTI)
+   thd->save_prep_leaf_list= TRUE;
+
   arena= thd->activate_stmt_arena_if_needed(&backup);  // For easier test
   derived->merged= TRUE;
 
-  if (!derived->merged_for_insert)
+  if (!derived->merged_for_insert || 
+      (derived->is_multitable() && 
+       (thd->lex->sql_command == SQLCOM_UPDATE_MULTI ||
+        thd->lex->sql_command == SQLCOM_DELETE_MULTI)))
   {
     /*
       Check whether there is enough free bits in table map to merge subquery.
@@ -392,7 +399,7 @@ bool mysql_derived_merge(THD *thd, LEX *lex, TABLE_LIST *derived)
     }
 
     /* Merge derived table's subquery in the parent select. */
-    if (parent_lex->merge_subquery(derived, dt_select, tablenr, map))
+    if (parent_lex->merge_subquery(thd, derived, dt_select, tablenr, map))
     {
       res= TRUE;
       goto exit_merge;
@@ -468,8 +475,6 @@ exit_merge:
 
 bool mysql_derived_merge_for_insert(THD *thd, LEX *lex, TABLE_LIST *derived)
 {
-  SELECT_LEX *dt_select= derived->get_single_select();
-
   if (derived->merged_for_insert)
     return FALSE;
   if (derived->is_materialized_derived())
@@ -482,43 +487,13 @@ bool mysql_derived_merge_for_insert(THD *thd, LEX *lex, TABLE_LIST *derived)
   {
     if (!derived->updatable)
       return derived->create_field_translation(thd);
-    TABLE_LIST *tl=((TABLE_LIST*)dt_select->table_list.first);
-    TABLE *table= tl->table;
-    /* preserve old map & tablenr. */
-    if (!derived->merged_for_insert && derived->table)
-      table->set_table_map(derived->table->map, derived->table->tablenr);
-
-    derived->table= table;
-    derived->schema_table=
-      ((TABLE_LIST*)dt_select->table_list.first)->schema_table;
-    if (!derived->merged)
+    if (derived->merge_underlying_list)
     {
-      Query_arena *arena, backup;
-      arena= thd->activate_stmt_arena_if_needed(&backup);  // For easier test
-      derived->select_lex->leaf_tables.push_back(tl);
-      derived->nested_join= (NESTED_JOIN*) thd->calloc(sizeof(NESTED_JOIN));
-      if (derived->nested_join)
-      {
-        derived->wrap_into_nested_join(tl->select_lex->top_join_list);
-        derived->get_unit()->exclude_level(); 
-      }
-      if (arena)
-        thd->restore_active_arena(arena, &backup);
-      derived->merged= TRUE;
-      if (!derived->nested_join)
-        return TRUE;
-    }      
-  }
-  else
-  {
-    if (thd->lex->sql_command == SQLCOM_UPDATE_MULTI ||
-        thd->lex->sql_command == SQLCOM_DELETE_MULTI)
-      thd->save_prep_leaf_list= TRUE;
-    if (!derived->merged_for_insert && mysql_derived_merge(thd, lex, derived))
-      return TRUE;
-  }
-  derived->merged_for_insert= TRUE;
-
+      derived->table= derived->merge_underlying_list->table;
+      derived->schema_table= derived->merge_underlying_list->schema_table;
+      derived->merged_for_insert= TRUE;
+    }
+  }  
   return FALSE;
 }
 
diff --git a/sql/sql_insert.cc b/sql/sql_insert.cc
index 72514d72dc1..05a30ab49a4 100644
--- a/sql/sql_insert.cc
+++ b/sql/sql_insert.cc
@@ -135,7 +135,7 @@ bool check_view_single_update(List<Item> &fields, List<Item> *values,
     A buffer for the insert values was allocated for the merged view.
     Use it.
   */
-  //tbl->table->insert_values= view->table->insert_values;
+  tbl->table->insert_values= view->table->insert_values;
   view->table= tbl->table;
   *map= tables;
 
diff --git a/sql/sql_lex.cc b/sql/sql_lex.cc
index e5abc896800..7ae2be9905c 100644
--- a/sql/sql_lex.cc
+++ b/sql/sql_lex.cc
@@ -1647,6 +1647,7 @@ void st_select_lex::init_select()
 {
   st_select_lex_node::init_select();
   sj_nests.empty();
+  sj_subselects.empty();
   group_list.empty();
   type= db= 0;
   having= 0;
@@ -3235,12 +3236,6 @@ bool st_select_lex::get_free_table_map(table_map *map, uint *tablenr)
   *map= 0;
   *tablenr= 0;
   TABLE_LIST *tl;
-  if (!join)
-  {
-    (*map)= 1<<1;
-    (*tablenr)++;
-    return FALSE;
-  }
   List_iterator<TABLE_LIST> ti(leaf_tables);
   while ((tl= ti++))
   {
@@ -3397,7 +3392,8 @@ void st_select_lex::remap_tables(TABLE_LIST *derived, table_map map,
   @return FALSE ok
 */
 
-bool SELECT_LEX::merge_subquery(TABLE_LIST *derived, SELECT_LEX *subq_select,
+bool SELECT_LEX::merge_subquery(THD *thd, TABLE_LIST *derived,
+                                SELECT_LEX *subq_select,
                                 uint table_no, table_map map)
 {
   derived->wrap_into_nested_join(subq_select->top_join_list);
@@ -3405,19 +3401,17 @@ bool SELECT_LEX::merge_subquery(TABLE_LIST *derived, SELECT_LEX *subq_select,
   leaf_tables.concat(&subq_select->leaf_tables);
 
   ftfunc_list->concat(subq_select->ftfunc_list);
-  if (join)
-  {
-    Item_in_subselect **in_subq;
-    Item_in_subselect **in_subq_end;
-    for (in_subq= subq_select->join->sj_subselects.front(), 
-         in_subq_end= subq_select->join->sj_subselects.back(); 
-         in_subq != in_subq_end; 
-         in_subq++)
+  if (join ||
+      thd->lex->sql_command == SQLCOM_UPDATE_MULTI ||
+      thd->lex->sql_command == SQLCOM_DELETE_MULTI)
+  {
+    List_iterator_fast<Item_in_subselect> li(subq_select->sj_subselects);
+    Item_in_subselect *in_subq;
+    while ((in_subq= li++))
     {
-      join->sj_subselects.append(join->thd->mem_root, *in_subq);
-      DBUG_ASSERT((*in_subq)->emb_on_expr_nest != NULL);
-      if ((*in_subq)->emb_on_expr_nest == NO_JOIN_NEST)
-        (*in_subq)->emb_on_expr_nest= derived;
+      sj_subselects.push_back(in_subq);
+      if (in_subq->emb_on_expr_nest == NO_JOIN_NEST)
+         in_subq->emb_on_expr_nest= derived;
     }
   }
   /*
diff --git a/sql/sql_lex.h b/sql/sql_lex.h
index 57eeb963b89..14ab445a366 100644
--- a/sql/sql_lex.h
+++ b/sql/sql_lex.h
@@ -637,6 +637,12 @@ public:
     tables. Unlike 'next_local', this in this list views are *not*
     leaves. Created in setup_tables() -> make_leaves_list().
   */
+  /* 
+    Subqueries that will need to be converted to semi-join nests, including
+    those converted to jtbm nests. The list is emptied when conversion is done.
+  */
+  List<Item_in_subselect> sj_subselects;
+
   List<TABLE_LIST> leaf_tables;
   List<TABLE_LIST> leaf_tables_exec;
   List<TABLE_LIST> leaf_tables_prep;
@@ -886,7 +892,7 @@ public:
   void remove_table_from_list(TABLE_LIST *table);
   void remap_tables(TABLE_LIST *derived, table_map map,
                     uint tablenr, st_select_lex *parent_lex);
-  bool merge_subquery(TABLE_LIST *derived, st_select_lex *subq_lex,
+  bool merge_subquery(THD *thd, TABLE_LIST *derived, st_select_lex *subq_lex,
                       uint tablenr, table_map map);
   inline bool is_mergeable()
   {
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index d42a4b869b3..ce0d4e95e3f 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -13033,7 +13033,7 @@ void setup_tmp_table_column_bitmaps(TABLE *table, uchar *bitmaps)
 */
 
 TABLE *
-create_tmp_table(THD *thd,TMP_TABLE_PARAM *param,List<Item> &fields,
+create_tmp_table(THD *thd, TMP_TABLE_PARAM *param, List<Item> &fields,
 		 ORDER *group, bool distinct, bool save_sum_fields,
 		 ulonglong select_options, ha_rows rows_limit,
                  char *table_alias, bool do_not_open)
diff --git a/sql/sql_select.h b/sql/sql_select.h
index ae21db849ff..cd91478fcf5 100644
--- a/sql/sql_select.h
+++ b/sql/sql_select.h
@@ -964,11 +964,6 @@ public:
   bool optimized; ///< flag to avoid double optimization in EXPLAIN
   bool initialized; ///< flag to avoid double init_execution calls
 
-  /* 
-    Subqueries that will need to be converted to semi-join nests, including
-    those converted to jtbm nests. The list is emptied when conversion is done.
-  */
-  Array<Item_in_subselect> sj_subselects;
   /*
     Additional WHERE and HAVING predicates to be considered for IN=>EXISTS
     subquery transformation of a JOIN object.
@@ -998,7 +993,7 @@ public:
 
   JOIN(THD *thd_arg, List<Item> &fields_arg, ulonglong select_options_arg,
        select_result *result_arg)
-    :fields_list(fields_arg), sj_subselects(thd_arg->mem_root, 4)
+    :fields_list(fields_arg)
   {
     init(thd_arg, fields_arg, select_options_arg, result_arg);
   }
diff --git a/sql/sql_update.cc b/sql/sql_update.cc
index 91be30b076b..b516065eff7 100644
--- a/sql/sql_update.cc
+++ b/sql/sql_update.cc
@@ -248,6 +248,7 @@ int mysql_update(THD *thd,
       DBUG_RETURN(1);
     close_tables_for_reopen(thd, &table_list);
   }
+
   if (table_list->handle_derived(thd->lex, DT_MERGE_FOR_INSERT))
     DBUG_RETURN(1);
   if (table_list->handle_derived(thd->lex, DT_PREPARE))
@@ -1037,10 +1038,10 @@ reopen_tables:
     second time, but this call will do nothing (there are check for second
     call in setup_tables()).
   */
+
   //We need to merge for insert prior to prepare.
   if (mysql_handle_derived(lex, DT_MERGE_FOR_INSERT))
     DBUG_RETURN(TRUE);
-
   if (mysql_handle_derived(lex, DT_PREPARE))
     DBUG_RETURN(TRUE);
 
@@ -1048,7 +1049,10 @@ reopen_tables:
                                     &lex->select_lex.top_join_list,
                                     table_list,
                                     lex->select_lex.leaf_tables, FALSE,
-                                    UPDATE_ACL, SELECT_ACL, TRUE))
+                                    UPDATE_ACL, SELECT_ACL, FALSE))
+    DBUG_RETURN(TRUE);
+
+  if (lex->select_lex.handle_derived(thd->lex, DT_MERGE))  
     DBUG_RETURN(TRUE);
 
   if (setup_fields_with_no_wrap(thd, 0, *fields, MARK_COLUMNS_WRITE, 0, 0))
@@ -1334,13 +1338,6 @@ int multi_update::prepare(List<Item> &not_used_values,
   thd->cuted_fields=0L;
   thd_proc_info(thd, "updating main table");
 
-  SELECT_LEX *select_lex= lex_unit->first_select();
-  if (select_lex->first_cond_optimization)
-  {
-    if (select_lex->handle_derived(thd->lex, DT_MERGE))
-      DBUG_RETURN(TRUE);
-  }
-
   tables_to_update= get_table_map(fields);
 
   if (!tables_to_update)