Merging 4.1 to 5.0.

BitKeeper/etc/ignore:
  auto-union
BitKeeper/etc/logging_ok:
  auto-union
client/mysqltest.c:
  Auto merged
configure.in:
  Auto merged
include/my_sys.h:
  Auto merged
include/mysql_com.h:
  Auto merged
libmysql/libmysql.c:
  Auto merged
libmysqld/Makefile.am:
  Auto merged
libmysqld/lib_sql.cc:
  Auto merged
myisam/mi_check.c:
  Auto merged
myisam/myisamchk.c:
  Auto merged
myisam/myisamdef.h:
  Auto merged
mysql-test/r/func_group.result:
  Auto merged
mysql-test/r/func_time.result:
  Auto merged
mysql-test/r/null.result:
  Auto merged
mysql-test/r/query_cache.result:
  Auto merged
mysql-test/r/rpl_server_id2.result:
  Auto merged
mysql-test/r/select.result:
  Auto merged
mysql-test/r/subselect.result:
  Auto merged
mysql-test/r/variables.result:
  Auto merged
mysql-test/t/rpl000015.test:
  Auto merged
mysql-test/t/rpl_error_ignored_table.test:
  Auto merged
mysql-test/t/rpl_log.test:
  Auto merged
mysql-test/t/rpl_log_pos.test:
  Auto merged
mysql-test/t/rpl_max_relay_size.test:
  Auto merged
mysql-test/t/rpl_relayrotate.test:
  Auto merged
mysql-test/t/rpl_rotate_logs.test:
  Auto merged
mysql-test/t/rpl_server_id2.test:
  Auto merged
mysql-test/t/subselect.test:
  Auto merged
mysql-test/t/variables.test:
  Auto merged
mysys/my_pthread.c:
  Auto merged
netware/BUILD/compile-netware-all:
  Auto merged
netware/BUILD/compile-netware-standard:
  Auto merged
netware/BUILD/mwenv:
  Auto merged
netware/Makefile.am:
  Auto merged
netware/my_manage.c:
  Auto merged
netware/my_manage.h:
  Auto merged
netware/mysql_test_run.c:
  Auto merged
scripts/mysql_install_db.sh:
  Auto merged
sql/Makefile.am:
  Auto merged
sql/ha_berkeley.cc:
  Auto merged
sql/ha_berkeley.h:
  Auto merged
sql/ha_innodb.cc:
  Auto merged
sql/ha_innodb.h:
  Auto merged
sql/ha_myisam.cc:
  Auto merged
sql/handler.cc:
  Auto merged
sql/handler.h:
  Auto merged
sql/item.cc:
  Auto merged
sql/item.h:
  Auto merged
sql/item_cmpfunc.cc:
  Auto merged
sql/item_func.cc:
  Auto merged
sql/item_subselect.cc:
  Auto merged
sql/item_subselect.h:
  Auto merged
sql/item_sum.cc:
  Auto merged
sql/item_sum.h:
  Auto merged
sql/item_timefunc.cc:
  Auto merged
sql/lock.cc:
  Auto merged
sql/mysql_priv.h:
  Auto merged
sql/opt_range.cc:
  Auto merged
sql/protocol.cc:
  Auto merged
sql/protocol.h:
  Auto merged
sql/repl_failsafe.cc:
  Auto merged
sql/set_var.cc:
  Auto merged
sql/sql_acl.cc:
  Auto merged
sql/sql_base.cc:
  Auto merged
sql/sql_cache.cc:
  Auto merged
sql/sql_class.cc:
  Auto merged
sql/sql_class.h:
  Auto merged
sql/sql_db.cc:
  Auto merged
sql/sql_insert.cc:
  Auto merged
sql/sql_parse.cc:
  Auto merged
sql/sql_prepare.cc:
  Auto merged
sql/sql_select.h:
  Auto merged
sql/sql_show.cc:
  Auto merged
sql/sql_string.cc:
  Auto merged
sql/sql_string.h:
  Auto merged
sql/sql_table.cc:
  Auto merged
sql/sql_union.cc:
  Auto merged
sql/sql_yacc.yy:
  Auto merged
tests/client_test.c:
  Auto merged

sql/sql_lex.h

@@ -351,6 +351,7 @@ public:
   st_select_lex *fake_select_lex;
 
   st_select_lex *union_distinct; /* pointer to the last UNION DISTINCT */
+  bool describe; /* union exec() called for EXPLAIN */
 
   void init_query();
   bool create_total_list(THD *thd, st_lex *lex, TABLE_LIST **result);
@@ -383,6 +384,7 @@ public:
   void print(String *str);
 
   ulong init_prepare_fake_select_lex(THD *thd);
+  int change_result(select_subselect *result, select_subselect *old_result);
   void set_limit(st_select_lex *values, st_select_lex *sl);
 
   friend void mysql_init_query(THD *thd, bool lexonly);
@@ -549,6 +551,20 @@ typedef class st_select_lex SELECT_LEX;
 #define ALTER_ORDER		64
 #define ALTER_OPTIONS		128
 
+typedef struct st_alter_info
+{
+  List<Alter_drop>            drop_list;
+  List<Alter_column>          alter_list;
+  uint                        flags;
+  enum enum_enable_or_disable keys_onoff;
+  enum tablespace_op_type     tablespace_op;
+  bool                        is_simple;
+
+  st_alter_info(){clear();}
+  void clear(){keys_onoff= LEAVE_AS_IS;tablespace_op= NO_TABLESPACE_OP;}
+  void reset(){drop_list.empty();alter_list.empty();clear();}
+} ALTER_INFO;
+
 struct st_sp_chistics
 {
   LEX_STRING comment;
@@ -589,8 +605,6 @@ typedef struct st_lex
 
   List<key_part_spec> col_list;
   List<key_part_spec> ref_list;
-  List<Alter_drop>    drop_list;
-  List<Alter_column>  alter_list;
   List<String>	      interval_list;
   List<LEX_USER>      users_list;
   List<LEX_COLUMN>    columns;
@@ -618,19 +632,17 @@ typedef struct st_lex
   enum enum_tx_isolation tx_isolation;
   enum enum_ha_read_modes ha_read_mode;
   enum ha_rkey_function ha_rkey_mode;
-  enum enum_enable_or_disable alter_keys_onoff;
   enum enum_var_type option_type;
-  enum tablespace_op_type tablespace_op;
   uint uint_geom_type;
   uint grant, grant_tot_col, which_columns;
   uint fk_delete_opt, fk_update_opt, fk_match_option;
   uint slave_thd_opt;
-  uint alter_flags;
   uint8 describe;
   bool drop_if_exists, drop_temporary, local_file;
-  bool in_comment, ignore_space, verbose, simple_alter, no_write_to_binlog;
+  bool in_comment, ignore_space, verbose, no_write_to_binlog;
   bool derived_tables;
   bool safe_to_cache_query;
+  ALTER_INFO alter_info;
   sp_head *sphead;
   sp_name *spname;
   bool sp_lex_in_use;	/* Keep track on lex usage in SPs for error handling */
@@ -684,6 +696,4 @@ void lex_end(LEX *lex);
 
 extern pthread_key(LEX*,THR_LEX);
 
-extern LEX_STRING tmp_table_alias;
-
 #define current_lex (current_thd->lex)