Fix for bug#12905 show fields from view behaving erratically with current database

  use saved view db name in case of view

mysql-test/r/information_schema.result

@@ -979,3 +979,14 @@ WHERE TABLE_SCHEMA='test' AND TABLE_TYPE='BASE TABLE');
 Name	Engine	Version	Row_format	Rows	Avg_row_length	Data_length	Max_data_length	Index_length	Data_free	Auto_increment	Create_time	Update_time	Check_time	Collation	Checksum	Create_options	Comment
 t1	MyISAM	10	Fixed	0	0	0	#	1024	0	NULL	#	#	NULL	latin1_swedish_ci	NULL		
 t2	MyISAM	10	Fixed	0	0	0	#	1024	0	NULL	#	#	NULL	latin1_swedish_ci	NULL		
+DROP TABLE t1,t2;
+create table t1(f1 int);
+create view v1 (c) as select f1 from t1;
+select database();
+database()
+NULL
+show fields from test.v1;
+Field	Type	Null	Key	Default	Extra
+c	int(11)	YES		NULL	
+drop view v1;
+drop table t1;

mysql-test/t/information_schema.test

@@ -665,4 +665,16 @@ SHOW TABLE STATUS FROM test
   WHERE name IN ( SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES
                     WHERE TABLE_SCHEMA='test' AND TABLE_TYPE='BASE TABLE');
 
-DROP TABLE t1,t2
+DROP TABLE t1,t2;
+
+#
+# Bug #12905 show fields from view behaving erratically with current database
+#
+create table t1(f1 int);
+create view v1 (c) as select f1 from t1;
+connect (con5,localhost,root,,*NO-ONE*);
+select database();
+show fields from test.v1;
+connection default;
+drop view v1;
+drop table t1;

sql/sql_show.cc

@@ -1988,9 +1988,19 @@ int get_all_tables(THD *thd, TABLE_LIST *tables, COND *cond)
     /*
       get_all_tables() returns 1 on failure and 0 on success thus
       return only these and not the result code of ::process_table()
+
+      We should use show_table_list->alias instead of 
+      show_table_list->table_name because table_name
+      could be changed during opening of I_S tables. It's safe
+      to use alias because alias contains original table name 
+      in this case(this part of code is used only for 
+      'show columns' & 'show statistics' commands).
     */
     error= test(schema_table->process_table(thd, show_table_list,
-                                    table, res, show_table_list->db,
+                                            table, res, 
+                                            (show_table_list->view ?
+                                             show_table_list->view_db.str :
+                                             show_table_list->db),
                                             show_table_list->alias));
     close_thread_tables(thd);
     show_table_list->table= 0;
@@ -2092,6 +2102,13 @@ int get_all_tables(THD *thd, TABLE_LIST *tables, COND *cond)
             lex->derived_tables= 0;
             res= open_normal_and_derived_tables(thd, show_table_list,
                                                 MYSQL_LOCK_IGNORE_FLUSH);
+            /*
+              We should use show_table_list->alias instead of 
+              show_table_list->table_name because table_name
+              could be changed during opening of I_S tables. It's safe
+              to use alias because alias contains original table name 
+              in this case.
+            */
             res= schema_table->process_table(thd, show_table_list, table,
                                             res, base_name,
                                             show_table_list->alias);