Faster alter table code for 5.1.

BitKeeper/etc/config

@@ -24,7 +24,7 @@ description: MySQL - fast and reliable SQL database
 # repository is commercial it can be an internal email address or "none"
 # to disable logging.
 # 
-logging:  logging@openlogging.org
+logging:  none
 # 
 # If this field is set, all checkins will appear to be made by this user,
 # in effect making this a single user package.  Single user packages are
@@ -73,3 +73,8 @@ hours:
 [nick:]checkout:get
 checkout:edit
 eoln:unix
+
+license: BKL5433d4e6925a06a150001200fff9b
+licsign1: YgAAAo0AAAADgAAAAEYUtZil1XCmH6z+LTlQMDJ+1ZeBLIgtHo1azUxQ8/8G1JuW
+licsign2: fxW3y9raSlpYVAleJSaBDKYiVtEuSdaUN2ILLo6Wc8TJmLl0aprUy7Lh/m/Sq/YC
+licsign3: 0H7qah3bdItuw7NGNSLfBzigbKOF6kPbU84VlAUhOqLR2e5Zf32SBZhtCYGA

mysql-test/r/alter_table.result

@@ -537,3 +537,57 @@ create table t1 ( a timestamp );
 alter table t1 add unique ( a(1) );
 ERROR HY000: Incorrect sub part key; the used key part isn't a string, the used length is longer than the key part, or the storage engine doesn't support unique sub keys
 drop table t1;
+create table t1 (v varchar(32));
+insert into t1 values ('def'),('abc'),('hij'),('3r4f');
+select * from t1;
+v
+def
+abc
+hij
+3r4f
+alter table t1 change v v2 varchar(32);
+select * from t1;
+v2
+def
+abc
+hij
+3r4f
+alter table t1 change v2 v varchar(64);
+select * from t1;
+v
+def
+abc
+hij
+3r4f
+update t1 set v = 'lmn' where v = 'hij';
+select * from t1;
+v
+def
+abc
+lmn
+3r4f
+alter table t1 add i int auto_increment not null primary key first;
+select * from t1;
+i	v
+1	def
+2	abc
+3	lmn
+4	3r4f
+update t1 set i=5 where i=3;
+select * from t1;
+i	v
+1	def
+2	abc
+5	lmn
+4	3r4f
+alter table t1 change i i bigint;
+select * from t1;
+i	v
+1	def
+2	abc
+5	lmn
+4	3r4f
+alter table t1 add unique key (i, v);
+select * from t1 where i between 2 and 4 and v in ('def','3r4f','lmn');
+i	v
+4	3r4f

mysql-test/t/alter_table.test

@@ -360,3 +360,30 @@ create table t1 ( a timestamp );
 --error 1089
 alter table t1 add unique ( a(1) );
 drop table t1;
+
+#
+# Some additional tests for new, faster alter table.
+# Note that most of the whole alter table code is being
+# tested all around the test suite already.
+#
+
+create table t1 (v varchar(32));
+insert into t1 values ('def'),('abc'),('hij'),('3r4f');
+select * from t1;
+# Fast alter, no copy performed
+alter table t1 change v v2 varchar(32);
+select * from t1;
+# Fast alter, no copy performed
+alter table t1 change v2 v varchar(64);
+select * from t1;
+update t1 set v = 'lmn' where v = 'hij';
+select * from t1;
+# Regular alter table
+alter table t1 add i int auto_increment not null primary key first;
+select * from t1;
+update t1 set i=5 where i=3;
+select * from t1;
+alter table t1 change i i bigint;
+select * from t1;
+alter table t1 add unique key (i, v);
+select * from t1 where i between 2 and 4 and v in ('def','3r4f','lmn');

sql/field.cc

@@ -65,6 +65,7 @@ inline int field_type2index (enum_field_types field_type)
           ((int)FIELDTYPE_TEAR_FROM) + (field_type - FIELDTYPE_TEAR_TO) - 1);
 }
 
+
 static enum_field_types field_types_merge_rules [FIELDTYPE_NUM][FIELDTYPE_NUM]=
 {
   /* MYSQL_TYPE_DECIMAL -> */
@@ -5920,6 +5921,26 @@ int Field_str::store(double nr)
 }
 
 
+uint Field::is_equal(create_field *new_field)
+{
+  return (new_field->sql_type == type());
+}
+
+
+uint Field_str::is_equal(create_field *new_field)
+{
+  if (((new_field->flags & (BINCMP_FLAG | BINARY_FLAG)) &&
+       !(flags & (BINCMP_FLAG | BINARY_FLAG))) ||
+      (!(new_field->flags & (BINCMP_FLAG | BINARY_FLAG)) &&
+	(flags & (BINCMP_FLAG | BINARY_FLAG))))
+    return 0; /* One of the fields is binary and the other one isn't */
+
+  return ((new_field->sql_type == type()) &&
+	  new_field->charset == field_charset &&
+	  new_field->length == max_length());
+}
+
+
 int Field_string::store(longlong nr)
 {
   char buff[64];
@@ -6676,6 +6697,22 @@ Field *Field_varstring::new_key_field(MEM_ROOT *root,
 }
 
 
+uint Field_varstring::is_equal(create_field *new_field)
+{
+  if (new_field->sql_type == type() &&
+      new_field->charset == field_charset)
+  {
+    if (new_field->length == max_length())
+      return IS_EQUAL_YES;
+    if (new_field->length > max_length() &&
+	((new_field->length <= 255 && max_length() <= 255) ||
+	 (new_field->length > 255 && max_length() > 255)))
+      return IS_EQUAL_PACK_LENGTH; // VARCHAR, longer variable length
+  }
+  return IS_EQUAL_NO;
+}
+
+
 /****************************************************************************
 ** blob type
 ** A blob is saved as a length and a pointer. The length is stored in the
@@ -7777,6 +7814,17 @@ bool Field_num::eq_def(Field *field)
 }
 
 
+uint Field_num::is_equal(create_field *new_field)
+{
+  return ((new_field->sql_type == type()) &&
+	  ((new_field->flags & UNSIGNED_FLAG) == (uint) (flags &
+							 UNSIGNED_FLAG)) &&
+	  ((new_field->flags & AUTO_INCREMENT_FLAG) ==
+	   (uint) (flags & AUTO_INCREMENT_FLAG)) &&
+	  (new_field->length >= max_length()));
+}
+
+
 /*
   Bit field.
 

sql/field.h

@@ -28,6 +28,7 @@
 
 class Send_field;
 class Protocol;
+class create_field;
 struct st_cache_field;
 void field_conv(Field *to,Field *from);
 
@@ -305,6 +306,8 @@ class Field
   int warn_if_overflow(int op_result);
   /* maximum possible display length */
   virtual uint32 max_length()= 0;
+
+  virtual uint is_equal(create_field *new_field);
   /* convert decimal to longlong with overflow check */
   longlong convert_decimal2longlong(const my_decimal *val, bool unsigned_flag,
                                     int *err);
@@ -345,6 +348,7 @@ class Field_num :public Field {
   bool eq_def(Field *field);
   int store_decimal(const my_decimal *);
   my_decimal *val_decimal(my_decimal *);
+  uint is_equal(create_field *new_field);
 };
 
 
@@ -369,6 +373,7 @@ class Field_str :public Field {
   uint32 max_length() { return field_length; }
   friend class create_field;
   my_decimal *val_decimal(my_decimal *);
+  uint is_equal(create_field *new_field);
 };
 
 
@@ -1082,6 +1087,7 @@ class Field_varstring :public Field_longstr {
   Field *new_key_field(MEM_ROOT *root, struct st_table *new_table,
                        char *new_ptr, uchar *new_null_ptr,
                        uint new_null_bit);
+  uint is_equal(create_field *new_field);
 };
 
 

sql/ha_berkeley.cc

@@ -2638,4 +2638,14 @@ int ha_berkeley::cmp_ref(const byte *ref1, const byte *ref2)
   return 0;
 }
 
+
+bool ha_berkeley::check_if_incompatible_data(HA_CREATE_INFO *info,
+					     uint table_changes)
+{
+  if (table_changes < IS_EQUAL_YES)
+    return COMPATIBLE_DATA_NO;
+  return COMPATIBLE_DATA_YES;
+}
+
+
 #endif /* HAVE_BERKELEY_DB */

sql/ha_berkeley.h

@@ -157,6 +157,7 @@ class ha_berkeley: public handler
   uint8 table_cache_type() { return HA_CACHE_TBL_TRANSACT; }
   bool primary_key_is_clustered() { return true; }
   int cmp_ref(const byte *ref1, const byte *ref2);
+  bool check_if_incompatible_data(HA_CREATE_INFO *info, uint table_changes);
 };
 
 extern bool berkeley_shared_data;

sql/ha_heap.cc

@@ -582,3 +582,15 @@ ulonglong ha_heap::get_auto_increment()
   ha_heap::info(HA_STATUS_AUTO);
   return auto_increment_value;
 }
+
+
+bool ha_heap::check_if_incompatible_data(HA_CREATE_INFO *info,
+					 uint table_changes)
+{
+  /* Check that auto_increment value was not changed */
+  if ((table_changes != IS_EQUAL_YES &&
+       info->used_fields & HA_CREATE_USED_AUTO) &&
+      info->auto_increment_value != 0)
+    return COMPATIBLE_DATA_NO;
+  return COMPATIBLE_DATA_YES;
+}

sql/ha_heap.h

@@ -103,6 +103,7 @@ class ha_heap: public handler
     HEAP_PTR ptr2=*(HEAP_PTR*)ref2;
     return ptr1 < ptr2? -1 : (ptr1 > ptr2? 1 : 0);
   }
+  bool check_if_incompatible_data(HA_CREATE_INFO *info, uint table_changes);
 private:
   void update_key_stats();
 };

sql/ha_innodb.cc

@@ -7038,4 +7038,24 @@ innobase_rollback_by_xid(
 	}
 }
 
+
+bool ha_innobase::check_if_incompatible_data(HA_CREATE_INFO *info,
+					     uint table_changes)
+{
+  if (table_changes != IS_EQUAL_YES)
+    return COMPATIBLE_DATA_NO;
+  
+  /* Check that auto_increment value was not changed */
+  if ((info->used_fields & HA_CREATE_USED_AUTO) &&
+      info->auto_increment_value != 0)
+    return COMPATIBLE_DATA_NO;
+  
+  /* Check that row format didn't change */
+  if ((info->used_fields & HA_CREATE_USED_AUTO) &&
+      get_row_type() != info->row_type)
+    return COMPATIBLE_DATA_NO;
+
+  return COMPATIBLE_DATA_YES;
+}
+
 #endif /* HAVE_INNOBASE_DB */

sql/ha_innodb.h

@@ -214,6 +214,8 @@ class ha_innobase: public handler
         static ulonglong get_mysql_bin_log_pos();
         bool primary_key_is_clustered() { return true; }
         int cmp_ref(const byte *ref1, const byte *ref2);
+	bool ha_innobase::check_if_incompatible_data(HA_CREATE_INFO *info,
+						     uint table_changes);
 };
 
 extern struct show_var_st innodb_status_variables[];

sql/ha_myisam.cc

@@ -1660,3 +1660,25 @@ uint ha_myisam::checksum() const
   return (uint)file->s->state.checksum;
 }
 
+
+bool ha_myisam::check_if_incompatible_data(HA_CREATE_INFO *info,
+					   uint table_changes)
+{
+  uint options= table->s->db_options_in_use;
+
+  if (info->auto_increment_value != auto_increment_value ||
+      info->raid_type != raid_type ||
+      info->raid_chunks != raid_chunks ||
+      info->raid_chunksize != raid_chunksize ||
+      info->data_file_name != data_file_name ||
+      info->index_file_name != index_file_name ||
+      table_changes == IS_EQUAL_NO)
+    return COMPATIBLE_DATA_NO;
+
+  if ((options & (HA_OPTION_PACK_RECORD | HA_OPTION_CHECKSUM |
+		  HA_OPTION_DELAY_KEY_WRITE)) !=
+      (info->table_options & (HA_OPTION_PACK_RECORD | HA_OPTION_CHECKSUM |
+			      HA_OPTION_DELAY_KEY_WRITE)))
+    return COMPATIBLE_DATA_NO;
+  return COMPATIBLE_DATA_YES;
+}

sql/ha_myisam.h

@@ -129,6 +129,7 @@ class ha_myisam: public handler
   int backup(THD* thd, HA_CHECK_OPT* check_opt);
   int assign_to_keycache(THD* thd, HA_CHECK_OPT* check_opt);
   int preload_keys(THD* thd, HA_CHECK_OPT* check_opt);
+  bool check_if_incompatible_data(HA_CREATE_INFO *info, uint table_changes);
 #ifdef HAVE_REPLICATION
   int dump(THD* thd, int fd);
   int net_read_dump(NET* net);

sql/ha_myisammrg.cc

@@ -488,3 +488,14 @@ void ha_myisammrg::append_create_info(String *packet)
   }
   packet->append(')');
 }
+
+
+bool ha_myisammrg::check_if_incompatible_data(HA_CREATE_INFO *info,
+					      uint table_changes)
+{
+  /*
+    For myisammrg, we should always re-generate the mapping file as this
+    is trivial to do
+  */
+  return COMPATIBLE_DATA_NO;
+}

sql/ha_myisammrg.h

@@ -82,4 +82,5 @@ class ha_myisammrg: public handler
   void update_create_info(HA_CREATE_INFO *create_info);
   void append_create_info(String *packet);
   MYRG_INFO *myrg_info() { return file; }
+  bool check_if_incompatible_data(HA_CREATE_INFO *info, uint table_changes);
 };

sql/ha_ndbcluster.cc

@@ -7233,4 +7233,26 @@ ha_ndbcluster::generate_scan_filter(Ndb_cond_stack *ndb_cond_stack,
   DBUG_RETURN(0);
 }
 
+
+bool ha_ndbcluster::check_if_incompatible_data(HA_CREATE_INFO *info,
+					       uint table_changes)
+{
+  return COMPATIBLE_DATA_NO;
+
+  if (table_changes != IS_EQUAL_YES)
+    return COMPATIBLE_DATA_NO;
+  
+  /* Check that auto_increment value was not changed */
+  if ((info->used_fields & HA_CREATE_USED_AUTO) &&
+      info->auto_increment_value != 0)
+    return COMPATIBLE_DATA_NO;
+  
+  /* Check that row format didn't change */
+  if ((info->used_fields & HA_CREATE_USED_AUTO) &&
+      get_row_type() != info->row_type)
+    return COMPATIBLE_DATA_NO;
+
+  return COMPATIBLE_DATA_YES;
+}
+
 #endif /* HAVE_NDBCLUSTER_DB */

sql/ha_ndbcluster.h

@@ -534,6 +534,10 @@ static void set_tabname(const char *pathname, char *tabname);
                                      uint key_length,
                                      qc_engine_callback *engine_callback,
                                      ulonglong *engine_data);
+
+  bool ha_ndbcluster::check_if_incompatible_data(HA_CREATE_INFO *info,
+						 uint table_changes);
+
 private:
   int alter_table_name(const char *to);
   int drop_table();

sql/handler.h

@@ -218,6 +218,9 @@ typedef ulonglong my_xid; // this line is the same as in log_event.h
 #define MAXGTRIDSIZE 64
 #define MAXBQUALSIZE 64
 
+#define COMPATIBLE_DATA_YES 0
+#define COMPATIBLE_DATA_NO  1
+
 struct xid_t {
   long formatID;
   long gtrid_length;
@@ -1005,6 +1008,9 @@ class handler :public Sql_alloc
      Pops the top if condition stack, if stack is not empty
  */
  virtual void cond_pop() { return; };
+ virtual bool check_if_incompatible_data(HA_CREATE_INFO *create_info,
+					 uint table_changes)
+ { return COMPATIBLE_DATA_NO; }
 };
 
 	/* Some extern variables used with handlers */

sql/mysql_priv.h

@@ -391,6 +391,13 @@ void debug_sync_point(const char* lock_name, uint lock_timeout);
 
 #define STRING_BUFFER_USUAL_SIZE 80
 
+/*
+  Some defines for exit codes for ::is_equal class functions.
+*/
+#define IS_EQUAL_NO 0
+#define IS_EQUAL_YES 1
+#define IS_EQUAL_PACK_LENGTH 2
+
 enum enum_parsing_place
 {
   NO_MATTER,

sql/mysqld.cc

@@ -4317,6 +4317,7 @@ enum options_mysqld
   OPT_ENABLE_SHARED_MEMORY,
   OPT_SHARED_MEMORY_BASE_NAME,
   OPT_OLD_PASSWORDS,
+  OPT_OLD_ALTER_TABLE,
   OPT_EXPIRE_LOGS_DAYS,
   OPT_GROUP_CONCAT_MAX_LEN,
   OPT_DEFAULT_COLLATION,
@@ -4836,6 +4837,11 @@ Disable with --skip-ndbcluster (will save memory).",
    (gptr*) &opt_no_mix_types, (gptr*) &opt_no_mix_types, 0, GET_BOOL, NO_ARG,
    0, 0, 0, 0, 0, 0},
 #endif
+  {"old-alter-table", OPT_OLD_ALTER_TABLE,
+   "Use old, non-optimized alter table.",
+   (gptr*) &global_system_variables.old_alter_table,
+   (gptr*) &max_system_variables.old_alter_table, 0, GET_BOOL, NO_ARG,
+   0, 0, 0, 0, 0, 0},
   {"old-passwords", OPT_OLD_PASSWORDS, "Use old password encryption method (needed for 4.0 and older clients).",
    (gptr*) &global_system_variables.old_passwords,
    (gptr*) &max_system_variables.old_passwords, 0, GET_BOOL, NO_ARG,
@@ -6016,6 +6022,7 @@ static void mysql_init_variables(void)
   global_system_variables.max_join_size= (ulonglong) HA_POS_ERROR;
   max_system_variables.max_join_size=   (ulonglong) HA_POS_ERROR;
   global_system_variables.old_passwords= 0;
+  global_system_variables.old_alter_table= 0;
 
   /* Variables that depends on compile options */
 #ifndef DBUG_OFF

sql/set_var.cc

@@ -284,6 +284,8 @@ sys_var_thd_ulong	sys_net_retry_count("net_retry_count",
 					    &SV::net_retry_count,
 					    0, fix_net_retry_count);
 sys_var_thd_bool	sys_new_mode("new", &SV::new_mode);
+sys_var_thd_bool	sys_old_alter_table("old_alter_table",
+					    &SV::old_alter_table);
 sys_var_thd_bool	sys_old_passwords("old_passwords", &SV::old_passwords);
 sys_var_thd_ulong       sys_optimizer_prune_level("optimizer_prune_level",
                                                   &SV::optimizer_prune_level);
@@ -630,6 +632,7 @@ sys_var *sys_variables[]=
   &sys_net_wait_timeout,
   &sys_net_write_timeout,
   &sys_new_mode,
+  &sys_old_alter_table,
   &sys_old_passwords,
   &sys_optimizer_prune_level,
   &sys_optimizer_search_depth,
@@ -903,6 +906,7 @@ struct show_var_st init_vars[]= {
   {sys_net_retry_count.name,  (char*) &sys_net_retry_count,	    SHOW_SYS},
   {sys_net_write_timeout.name,(char*) &sys_net_write_timeout,       SHOW_SYS},
   {sys_new_mode.name,         (char*) &sys_new_mode,                SHOW_SYS},
+  {sys_old_alter_table.name,  (char*) &sys_old_alter_table,         SHOW_SYS},
   {sys_old_passwords.name,    (char*) &sys_old_passwords,           SHOW_SYS},
   {"open_files_limit",	      (char*) &open_files_limit,	    SHOW_LONG},
   {sys_optimizer_prune_level.name, (char*) &sys_optimizer_prune_level,

sql/set_var.h

@@ -882,6 +882,7 @@ class NAMED_LIST :public ilink
 
 /* updated in sql_acl.cc */
 
+extern sys_var_thd_bool sys_old_alter_table;
 extern sys_var_thd_bool sys_old_passwords;
 extern LEX_STRING default_key_cache_base;
 

sql/sql_class.h

@@ -564,6 +564,7 @@ struct system_variables
   my_bool ndb_use_exact_count;
   my_bool ndb_use_transactions;
 #endif /* HAVE_NDBCLUSTER_DB */
+  my_bool old_alter_table;
   my_bool old_passwords;
   
   /* Only charset part of these variables is sensible */

sql/sql_lex.h

@@ -645,6 +645,7 @@ typedef class st_select_lex SELECT_LEX;
 #define ALTER_KEYS_ONOFF        512
 #define ALTER_CONVERT          1024
 #define ALTER_FORCE		2048
+#define ALTER_RECREATE          4096
 
 typedef struct st_alter_info
 {

sql/sql_table.cc

@@ -1348,6 +1348,34 @@ static int mysql_prepare_table(THD *thd, HA_CREATE_INFO *create_info,
 }
 
 
+/*
+  Set table default charset, if not set
+
+  SYNOPSIS
+    set_table_default_charset()
+    create_info        Table create information
+
+  DESCRIPTION
+    If the table character set was not given explicitely,
+    let's fetch the database default character set and
+    apply it to the table.
+*/
+
+static void set_table_default_charset(THD *thd,
+				      HA_CREATE_INFO *create_info, char *db)
+{
+  if (!create_info->default_table_charset)
+  {
+    HA_CREATE_INFO db_info;
+    char path[FN_REFLEN];
+    /* Abuse build_table_path() to build the path to the db.opt file */
+    build_table_path(path, sizeof(path), db, MY_DB_OPT_FILE, "");
+    load_db_opt(thd, path, &db_info);
+    create_info->default_table_charset= db_info.default_table_charset;
+  }
+}
+
+
 /*
   Extend long VARCHAR fields to blob & prepare field if it's a blob
 
@@ -1532,20 +1560,7 @@ bool mysql_create_table(THD *thd,const char *db, const char *table_name,
   }
 #endif
 
-  /*
-    If the table character set was not given explicitely,
-    let's fetch the database default character set and
-    apply it to the table.
-  */
-  if (!create_info->default_table_charset)
-  {
-    HA_CREATE_INFO db_info;
-    char  path[FN_REFLEN];
-    /* Abuse build_table_path() to build the path to the db.opt file */
-    build_table_path(path, sizeof(path), db, MY_DB_OPT_FILE, "");
-    load_db_opt(thd, path, &db_info);
-    create_info->default_table_charset= db_info.default_table_charset;
-  }
+  set_table_default_charset(thd, create_info, (char*) db);
 
   if (mysql_prepare_table(thd, create_info, &fields,
 			  &keys, internal_tmp_table, &db_options, file,
@@ -3029,6 +3044,166 @@ int mysql_drop_indexes(THD *thd, TABLE_LIST *table_list,
 #endif /* NOT_USED */
 
 
+
+#define ALTER_TABLE_DATA_CHANGED  1
+#define ALTER_TABLE_INDEX_CHANGED 2
+
+/*
+  SYNOPSIS
+    compare tables()
+    table       original table
+    create_list fields in new table
+    key_list    keys in new table
+    create_info create options in new table
+
+  DESCRIPTION
+    'table' (first argument) contains information of the original
+    table, which includes all corresponding parts that the new
+    table has in arguments create_list, key_list and create_info.
+
+    By comparing the changes between the original and new table
+    we can determine how much it has changed after ALTER TABLE
+    and whether we need to make a copy of the table, or just change
+    the .frm file.
+
+  RETURN VALUES
+    0 No copy needed
+    1 Data changes, copy needed
+    2 Index changes, copy needed   
+*/
+
+uint compare_tables(TABLE *table, List<create_field> *create_list,
+		    List<Key> *key_list, HA_CREATE_INFO *create_info,
+		    ALTER_INFO *alter_info, uint order_num)
+{
+  Field **f_ptr, *field;
+  uint changes= 0, tmp;
+  List_iterator_fast<create_field> new_field_it(*create_list);
+  create_field *new_field;
+
+  /*
+    Some very basic checks. If number of fields changes, or the
+    handler, we need to run full ALTER TABLE. In the future
+    new fields can be added and old dropped without copy, but
+    not yet.
+
+    Test also that engine was not given during ALTER TABLE, or
+    we are force to run regular alter table (copy).
+    E.g. ALTER TABLE tbl_name ENGINE=MyISAM.
+
+    For the following ones we also want to run regular alter table:
+    ALTER TABLE tbl_name ORDER BY ..
+    ALTER TABLE tbl_name CONVERT TO CHARACTER SET ..
+
+    At the moment we can't handle altering temporary tables without a copy.
+    We also test if OPTIMIZE TABLE was given and was mapped to alter table.
+    In that case we always do full copy.
+  */
+  if (table->s->fields != create_list->elements ||
+      table->s->db_type != create_info->db_type ||
+      table->s->tmp_table ||
+      create_info->used_fields & HA_CREATE_USED_ENGINE ||
+      create_info->used_fields & HA_CREATE_USED_CHARSET ||
+      create_info->used_fields & HA_CREATE_USED_DEFAULT_CHARSET ||
+      (alter_info->flags & ALTER_RECREATE) ||
+      order_num)
+    return ALTER_TABLE_DATA_CHANGED;
+
+  /*
+    Go through fields and check if the original ones are compatible
+    with new table.
+  */
+  for (f_ptr= table->field, new_field= new_field_it++;
+       (field= *f_ptr); f_ptr++, new_field= new_field_it++)
+  {
+    /* Make sure we have at least the default charset in use. */
+    if (!new_field->charset)
+      new_field->charset= create_info->default_table_charset;
+    
+    /* Check that NULL behavior is same for old and new fields */
+    if ((new_field->flags & NOT_NULL_FLAG) !=
+	(uint) (field->flags & NOT_NULL_FLAG))
+      return ALTER_TABLE_DATA_CHANGED;
+
+    /* Don't pack rows in old tables if the user has requested this. */
+    if (create_info->row_type == ROW_TYPE_DYNAMIC ||
+	(new_field->flags & BLOB_FLAG) ||
+	new_field->sql_type == MYSQL_TYPE_VARCHAR &&
+	create_info->row_type != ROW_TYPE_FIXED)
+      create_info->table_options|= HA_OPTION_PACK_RECORD;
+
+    /* Evaluate changes bitmap and send to check_if_incompatible_data() */
+    if (!(tmp= field->is_equal(new_field)))
+      return ALTER_TABLE_DATA_CHANGED;
+
+    changes|= tmp;
+  }
+  /* Check if changes are compatible with current handler without a copy */
+  if (table->file->check_if_incompatible_data(create_info, changes))
+    return ALTER_TABLE_DATA_CHANGED;
+
+  /*
+    Go through keys and check if the original ones are compatible
+    with new table.
+  */
+  KEY *table_key_info= table->key_info;
+  List_iterator_fast<Key> key_it(*key_list);
+  Key *key= key_it++;
+
+  /* Check if the number of key elements has changed */
+  if  (table->s->keys != key_list->elements)
+    return ALTER_TABLE_INDEX_CHANGED;
+
+  for (uint i= 0; i < table->s->keys; i++, table_key_info++, key= key_it++)
+  {
+    /*
+      Check that the key types are compatible between old and new tables.
+    */
+    if (table_key_info->algorithm != key->algorithm ||
+	((key->type == Key::PRIMARY || key->type == Key::UNIQUE) &&
+	 !(table_key_info->flags & HA_NOSAME)) ||
+	(!(key->type == Key::PRIMARY || key->type == Key::UNIQUE) &&
+	 (table_key_info->flags & HA_NOSAME)) ||
+	((key->type == Key::SPATIAL) &&
+	 !(table_key_info->flags & HA_SPATIAL)) ||
+	(!(key->type == Key::SPATIAL) &&
+	 (table_key_info->flags & HA_SPATIAL)) ||
+	((key->type == Key::FULLTEXT) &&
+	 !(table_key_info->flags & HA_FULLTEXT)) ||
+	(!(key->type == Key::FULLTEXT) &&
+	 (table_key_info->flags & HA_FULLTEXT)))
+      return ALTER_TABLE_INDEX_CHANGED;
+    
+    if  (table_key_info->key_parts != key->columns.elements)
+      return ALTER_TABLE_INDEX_CHANGED;
+
+    /*
+      Check that the key parts remain compatible between the old and
+      new tables.
+    */
+    KEY_PART_INFO *table_key_part= table_key_info->key_part;
+    List_iterator_fast<key_part_spec> key_part_it(key->columns);
+    key_part_spec *key_part= key_part_it++;
+    for (uint j= 0; j < table_key_info->key_parts; j++,
+	   table_key_part++, key_part= key_part_it++)
+    {
+      /*
+	Key definition has changed if we are using a different field or
+	if the used key length is different
+	(If key_part->length == 0 it means we are using the whole field)
+      */
+      if (strcmp(key_part->field_name, table_key_part->field->field_name) ||
+	  (key_part->length && key_part->length != table_key_part->length) ||
+	  (key_part->length == 0 && table_key_part->length !=
+	   table_key_part->field->pack_length()))
+	return ALTER_TABLE_INDEX_CHANGED;	
+    }
+  }
+
+  return 0; // Tables are compatible
+}
+
+
 /*
   Alter table
 */
@@ -3050,7 +3225,7 @@ bool mysql_alter_table(THD *thd,char *new_db, char *new_name,
   ulonglong next_insert_id;
   uint db_create_options, used_fields;
   enum db_type old_db_type,new_db_type;
-  bool need_copy_table;
+  uint need_copy_table= 0;
   DBUG_ENTER("mysql_alter_table");
 
   thd->proc_info="init";
@@ -3282,8 +3457,8 @@ bool mysql_alter_table(THD *thd,char *new_db, char *new_name,
 	def_it.remove();
       }
     }
-    else
-    {						// Use old field value
+    else // This field was not dropped and not changed, add it to the list
+    {	 // for the new table.   
       create_list.push_back(def=new create_field(field,field));
       alter_it.rewind();			// Change default if ALTER
       Alter_column *alter;
@@ -3495,17 +3670,22 @@ bool mysql_alter_table(THD *thd,char *new_db, char *new_name,
   if (table->s->tmp_table)
     create_info->options|=HA_LEX_CREATE_TMP_TABLE;
 
+  set_table_default_charset(thd, create_info, db);
+
+  if (thd->variables.old_alter_table)
+    need_copy_table= 1;
+  else
+    need_copy_table= compare_tables(table, &create_list, &key_list,
+				    create_info, alter_info, order_num);
+
   /*
     better have a negative test here, instead of positive, like
     alter_info->flags & ALTER_ADD_COLUMN|ALTER_ADD_INDEX|...
     so that ALTER TABLE won't break when somebody will add new flag
   */
-  need_copy_table= (alter_info->flags &
-                    ~(ALTER_CHANGE_COLUMN_DEFAULT|ALTER_OPTIONS) ||
-                    (create_info->used_fields &
-                     ~(HA_CREATE_USED_COMMENT|HA_CREATE_USED_PASSWORD)) ||
-                    table->s->tmp_table);
-  create_info->frm_only= !need_copy_table;
+
+  if (!need_copy_table)
+    create_info->frm_only= 1;
 
   /*
     Handling of symlinked tables:
@@ -3811,7 +3991,7 @@ bool mysql_alter_table(THD *thd,char *new_db, char *new_name,
  err:
   DBUG_RETURN(TRUE);
 }
-
+/* mysql_alter_table */
 
 static int
 copy_data_between_tables(TABLE *from,TABLE *to,
@@ -4023,7 +4203,7 @@ bool mysql_recreate_table(THD *thd, TABLE_LIST *table_list,
   create_info.row_type=ROW_TYPE_NOT_USED;
   create_info.default_table_charset=default_charset_info;
   /* Force alter table to recreate table */
-  lex->alter_info.flags= ALTER_CHANGE_COLUMN;
+  lex->alter_info.flags= (ALTER_CHANGE_COLUMN | ALTER_RECREATE);
   DBUG_RETURN(mysql_alter_table(thd, NullS, NullS, &create_info,
                                 table_list, lex->create_list,
                                 lex->key_list, 0, (ORDER *) 0,