fulltext+const_table bug fixed

mysql-test/r/fulltext.result:
  test added
mysql-test/t/fulltext.test:
  test added
sql/item_func.cc:
  fulltext+const_table problem fixed once and forever
sql/item_func.h:
  fulltext+const_table problem fixed once and forever
sql/sql_select.cc:
  fulltext+const_table problem fixed once and forever
sql/table.h:
  fulltext+const_table problem fixed once and forever

mysql-test/r/fulltext.result

@@ -150,3 +150,9 @@ select * from t1;
 id	title
 1	this test once revealed a bug
 update t1 set title=NULL where id=1;
+drop table t1;
+CREATE TABLE t1 (a int(11), b text, FULLTEXT KEY (b)) TYPE=MyISAM;
+insert into t1 values (1,"I wonder why the fulltext index doesnt work?");
+SELECT * from t1 where MATCH (b) AGAINST ('apples');
+a	b
+drop table t1;

mysql-test/t/fulltext.test

@@ -129,3 +129,13 @@ check table t1;
 update t1 set title='this test once revealed a bug' where id=1;
 select * from t1;
 update t1 set title=NULL where id=1;
+
+drop table t1;
+
+# one more bug - const_table related
+
+CREATE TABLE t1 (a int(11), b text, FULLTEXT KEY (b)) TYPE=MyISAM;
+insert into t1 values (1,"I wonder why the fulltext index doesnt work?");
+SELECT * from t1 where MATCH (b) AGAINST ('apples');
+
+drop table t1;

sql/item_func.cc

@@ -2108,6 +2108,7 @@ bool Item_func_match::fix_fields(THD *thd,struct st_table_list *tlist)
       key=NO_SUCH_KEY;
   const_item_cache=0;
   table=((Item_field *)fields.head())->field->table;
+  table->fulltext_searched=1;
   record=table->record[0];
   if (key == NO_SUCH_KEY && mode != FT_BOOL)
   {

sql/item_func.h

@@ -930,6 +930,7 @@ public:
       ft_handler=0;
       if(join_key)
 	table->file->ft_handler=0;
+      table->fulltext_searched=0;
     }
     if (concat) delete concat;
   }

sql/sql_select.cc

@@ -982,7 +982,8 @@ make_join_statistics(JOIN *join,TABLE_LIST *tables,COND *conds,
       s->dependent=(table_map) 0;
     s->key_dependent=(table_map) 0;
     if ((table->system || table->file->records <= 1) && ! s->dependent &&
-	!(table->file->option_flag() & HA_NOT_EXACT_COUNT))
+	!(table->file->option_flag() & HA_NOT_EXACT_COUNT) &&
+        !table->fulltext_searched)
     {
       set_position(join,const_count++,s,(KEYUSE*) 0);
     }

sql/table.h

@@ -95,6 +95,7 @@ struct st_table {
   my_bool db_low_byte_first;		/* Portable row format */
   my_bool locked_by_flush;
   my_bool locked_by_name;
+  my_bool fulltext_searched;
   my_bool crashed;
   my_bool is_view;
   my_bool no_keyread;