MWL#90: Address review feedback part #4

sql/opt_subselect.cc

@@ -687,18 +687,22 @@ bool convert_join_subqueries_to_semijoins(JOIN *join)
   arena= thd->activate_stmt_arena_if_needed(&backup);
  
   for (in_subq= join->sj_subselects.front(); 
-       in_subq != in_subq_end && 
-       join->tables + (*in_subq)->unit->first_select()->join->tables < MAX_TABLES;
+       in_subq != in_subq_end;
        in_subq++)
   {
     bool remove_item= TRUE;
     if ((*in_subq)->is_flattenable_semijoin) 
     {
+      if (join->tables + 
+          (*in_subq)->unit->first_select()->join->tables >= MAX_TABLES)
+        break;
       if (convert_subq_to_sj(join, *in_subq))
         DBUG_RETURN(TRUE);
     }
     else
     {
+      if (join->tables + 1 >= MAX_TABLES)
+        break;
       if (convert_subq_to_jtbm(join, *in_subq, &remove_item))
         DBUG_RETURN(TRUE);
     }
@@ -1211,6 +1215,17 @@ static bool convert_subq_to_sj(JOIN *parent_join, Item_in_subselect *subq_pred)
 }
 
 
+const int SUBQERY_TEMPTABLE_NAME_MAX_LEN= 20;
+
+static void create_subquery_temptable_name(char *to, uint number)
+{
+  DBUG_ASSERT(number < 10000);       
+  to= strmov(to, "<subquery");
+  to= int10_to_str((int) number, to, 10);
+  to[0]= '>';
+  to[1]= 0;
+}
+
 /*
   Convert subquery predicate into non-mergeable semi-join nest.
 
@@ -1241,15 +1256,15 @@ static bool convert_subq_to_jtbm(JOIN *parent_join,
   if (subq_pred->engine->engine_type() != subselect_engine::HASH_SJ_ENGINE)
   {
     *remove_item= FALSE;
-    make_in_exists_conversion(parent_join->thd, parent_join, subq_pred);
-    DBUG_RETURN(FALSE);
+    bool res;
+    res= make_in_exists_conversion(parent_join->thd, parent_join, subq_pred);
+    DBUG_RETURN(res);
   }
   *remove_item= TRUE;
 
   TABLE_LIST *jtbm;
   char *tbl_alias;
-  const char alias_mask[]="<subquery%d>";
-  if (!(tbl_alias= (char*)parent_join->thd->calloc(sizeof(alias_mask)+5)) || 
+  if (!(tbl_alias= (char*)parent_join->thd->calloc(SUBQERY_TEMPTABLE_NAME_MAX_LEN)) ||
       !(jtbm= alloc_join_nest(parent_join->thd))) //todo: this is not a join nest!
   {
     DBUG_RETURN(TRUE);
@@ -1268,7 +1283,8 @@ static bool convert_subq_to_jtbm(JOIN *parent_join,
     Inject the jtbm table into TABLE_LIST::next_leaf list, so that 
     make_join_statistics() and co. can find it.
   */
-  for (tl= parent_lex->leaf_tables; tl->next_leaf; tl= tl->next_leaf) ;
+  for (tl= parent_lex->leaf_tables; tl->next_leaf; tl= tl->next_leaf)
+  {}
   tl->next_leaf= jtbm;
 
   /*
@@ -1276,7 +1292,8 @@ static bool convert_subq_to_jtbm(JOIN *parent_join,
     (a theory: a next_local chain always starts with ::leaf_tables
      because view's tables are inserted after the view)
   */
-  for (tl= parent_lex->leaf_tables; tl->next_local; tl= tl->next_local) ;
+  for (tl= parent_lex->leaf_tables; tl->next_local; tl= tl->next_local)
+  {}
   tl->next_local= jtbm;
 
   /* A theory: no need to re-connect the next_global chain */
@@ -1289,14 +1306,15 @@ static bool convert_subq_to_jtbm(JOIN *parent_join,
   jtbm->table->map= table_map(1) << (parent_join->tables);
 
   parent_join->tables++;
+  DBUG_ASSERT(parent_join->tables < MAX_TABLES);
 
   Item *conds= hash_sj_engine->semi_join_conds;
   conds->fix_after_pullout(parent_lex, &conds);
 
   DBUG_EXECUTE("where", print_where(conds,"SJ-EXPR", QT_ORDINARY););
   
-  my_snprintf(tbl_alias, sizeof(alias_mask)+5, alias_mask, 
-    hash_sj_engine->materialize_join->select_lex->select_number);
+  create_subquery_temptable_name(tbl_alias, hash_sj_engine->materialize_join->
+                                              select_lex->select_number);
   jtbm->alias= tbl_alias;
 
   /* Inject sj_on_expr into the parent's WHERE or ON */
@@ -4017,13 +4035,13 @@ enum_nested_loop_state join_tab_execution_startup(JOIN_TAB *tab)
   {
     /* It's a merged SJM nest */
     enum_nested_loop_state rc;
-    JOIN *join= tab->join;
     SJ_MATERIALIZATION_INFO *sjm= tab->bush_children->start->emb_sj_nest->sj_mat_info;
-    JOIN_TAB *join_tab= tab->bush_children->start;
-    JOIN_TAB *save_return_tab= join->return_tab;
 
     if (!sjm->materialized)
     {
+      JOIN *join= tab->join;
+      JOIN_TAB *join_tab= tab->bush_children->start;
+      JOIN_TAB *save_return_tab= join->return_tab;
       /*
         Now run the join for the inner tables. The first call is to run the
         join, the second one is to signal EOF (this is essential for some

sql/sql_base.cc

@@ -7784,7 +7784,7 @@ bool setup_tables(THD *thd, Name_resolution_context *context,
       Item *item= table_list->jtbm_subselect;
       if (item->fix_fields(thd, &item))
       {
-        my_error(ER_TOO_MANY_TABLES,MYF(0),MAX_TABLES);
+        my_error(ER_TOO_MANY_TABLES,MYF(0),MAX_TABLES); /* psergey-todo: WHY ER_TOO_MANY_TABLES ???*/
         DBUG_RETURN(1);
       }
       DBUG_ASSERT(item == table_list->jtbm_subselect);

sql/sql_select.cc

@@ -6991,9 +6991,8 @@ JOIN::make_simple_join(JOIN *parent, TABLE *temp_table)
 
   join_tab= parent->join_tab_reexec;
   table= &parent->table_reexec[0]; parent->table_reexec[0]= temp_table;
-  top_jtrange_tables= 1;
+  tables= top_jtrange_tables= 1;
 
-  tables= 1;
   const_tables= 0;
   const_table_map= 0;
   eliminated_tables= 0;
@@ -8417,11 +8416,8 @@ no_join_cache:
 void check_join_cache_usage_for_tables(JOIN *join, ulonglong options,
                                        uint no_jbuf_after)
 {
-  //JOIN_TAB *first_sjm_table= NULL;
-  //JOIN_TAB *last_sjm_table= NULL;
   JOIN_TAB *tab;
 
-  //for (uint i= join->const_tables; i < join->tables; i++)
   for (tab= first_linear_tab(join, TRUE); 
        tab; 
        tab= next_linear_tab(join, tab, TRUE))
@@ -8429,23 +8425,10 @@ void check_join_cache_usage_for_tables(JOIN *join, ulonglong options,
     tab->used_join_cache_level= join->max_allowed_join_cache_level;  
   }
 
-  //for (uint i= join->const_tables; i < join->tables; i++)
   for (tab= first_linear_tab(join, TRUE); 
        tab; 
        tab= next_linear_tab(join, tab, TRUE))
   {
-#if 0
-    if (sj_is_materialize_strategy(join->best_positions[i].sj_strategy))
-    {
-      first_sjm_table= tab;
-      last_sjm_table= tab + join->best_positions[i].n_sj_tables;
-      for (JOIN_TAB *sjm_tab= first_sjm_table;
-             sjm_tab != last_sjm_table; sjm_tab++)
-        sjm_tab->first_sjm_sibling= first_sjm_table;
-    } 
-    if (!(tab >= first_sjm_table && tab < last_sjm_table))
-      tab->first_sjm_sibling= NULL;
-#endif 
     JOIN_TAB *prev_tab;
 restart:
     tab->icp_other_tables_ok= TRUE;
@@ -8471,10 +8454,6 @@ restart:
         we can first allocate a join buffer, then decide not to use it and free
         it.
       */
-      /*
-      if (join->return_tab)
-        i= join->return_tab-join->join_tab-1;   // always >= 0
-      */
       if (join->return_tab)
       {
         tab= join->return_tab;
@@ -19617,14 +19596,21 @@ static void select_describe(JOIN *join, bool need_tmp_table, bool need_order,
             examined_rows= tab->limit;
           else
           {
-            //tab->table->file->info(HA_STATUS_VARIABLE);
             if (!tab->table->pos_in_table_list ||
                 tab->table->is_filled_at_execution()) // temporary, is_filled_at_execution
+            {
               examined_rows= tab->records;
+            }
             else
+            {
+              /*
+                handler->info(HA_STATUS_VARIABLE) has been called in
+                make_join_statistics()
+              */
               examined_rows= tab->table->file->stats.records;
             }
           }
+        }
         else
           examined_rows=(ha_rows)tab->records_read; 
  

sql/sql_show.cc

@@ -6600,14 +6600,12 @@ int make_schema_select(THD *thd, SELECT_LEX *sel,
 bool get_schema_tables_result(JOIN *join,
                               enum enum_schema_table_state executed_place)
 {
-  //JOIN_TAB *tmp_join_tab= join->join_tab+join->tables;
   THD *thd= join->thd;
   LEX *lex= thd->lex;
   bool result= 0;
   DBUG_ENTER("get_schema_tables_result");
 
   thd->no_warnings_for_error= 1;
-  //for (JOIN_TAB *tab= join->join_tab; tab < tmp_join_tab; tab++)
   for (JOIN_TAB *tab= first_linear_tab(join, FALSE); 
        tab; 
        tab= next_linear_tab(join, tab, FALSE))