mariadb/sql/sql_db.cc

/* Copyright (C) 2000-2003 MySQL AB

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */


/* create and drop of databases */

#include "mysql_priv.h"
#include <mysys_err.h>
#include "sql_acl.h"
#include <my_dir.h>
#include <m_ctype.h>
#ifdef __WIN__
#include <direct.h>
#endif

const char *del_exts[]= {".frm", ".BAK", ".TMD",".opt", NullS};
static TYPELIB deletable_extentions=
{array_elements(del_exts)-1,"del_exts", del_exts, NULL};

static long mysql_rm_known_files(THD *thd, MY_DIR *dirp,
				 const char *db, const char *path,
				 uint level);

/* Database options hash */
static HASH dboptions;
static my_bool dboptions_init= 0;
static rw_lock_t LOCK_dboptions;

/* Structure for database options */
typedef struct my_dbopt_st
{
  char *name;			/* Database name                  */
  uint name_length;		/* Database length name           */
  CHARSET_INFO *charset;	/* Database default character set */
} my_dbopt_t;


/*
  Function we use in the creation of our hash to get key.
*/
static byte* dboptions_get_key(my_dbopt_t *opt, uint *length,
                               my_bool not_used __attribute__((unused)))
{
  *length= opt->name_length;
  return (byte*) opt->name;
}


/*
  Function to free dboptions hash element
*/

static void free_dbopt(void *dbopt)
{
  my_free((gptr) dbopt, MYF(0));
}


/* 
  Initialize database option hash

  SYNOPSIS
    my_dbopt_init()

  NOTES
    Must be called before any other database function is called.

  RETURN
    0	ok
    1	Fatal error
*/

bool my_dbopt_init(void)
{
  bool error= 0;
  (void) my_rwlock_init(&LOCK_dboptions, NULL);
  if (!dboptions_init)
  {
    dboptions_init= 1;
    error= hash_init(&dboptions, lower_case_table_names ? 
                     &my_charset_bin : system_charset_info,
                     32, 0, 0, (hash_get_key) dboptions_get_key,
                     free_dbopt,0);
  }
  return error;
}


/* 
  Free database option hash.
*/

void my_dbopt_free(void)
{
  if (dboptions_init)
  {
    dboptions_init= 0;
    hash_free(&dboptions);
    (void) rwlock_destroy(&LOCK_dboptions);
  }
}


void my_dbopt_cleanup(void)
{
  rw_wrlock(&LOCK_dboptions);
  hash_free(&dboptions);
  hash_init(&dboptions, lower_case_table_names ? 
            &my_charset_bin : system_charset_info,
            32, 0, 0, (hash_get_key) dboptions_get_key,
            free_dbopt,0);
  rw_unlock(&LOCK_dboptions);
}


/*
  Find database options in the hash.
  
  DESCRIPTION
    Search a database options in the hash, usings its path.
    Fills "create" on success.
  
  RETURN VALUES
    0 on success.
    1 on error.
*/

static my_bool get_dbopt(const char *dbname, HA_CREATE_INFO *create)
{
  my_dbopt_t *opt;
  uint length;
  my_bool error= 1;
  
  length= (uint) strlen(dbname);
  
  rw_rdlock(&LOCK_dboptions);
  if ((opt= (my_dbopt_t*) hash_search(&dboptions, (byte*) dbname, length)))
  {
    create->default_table_charset= opt->charset;
    error= 0;
  }
  rw_unlock(&LOCK_dboptions);
  return error;
}


/*
  Writes database options into the hash.
  
  DESCRIPTION
    Inserts database options into the hash, or updates
    options if they are already in the hash.
  
  RETURN VALUES
    0 on success.
    1 on error.
*/

static my_bool put_dbopt(const char *dbname, HA_CREATE_INFO *create)
{
  my_dbopt_t *opt;
  uint length;
  my_bool error= 0;
  DBUG_ENTER("put_dbopt");

  length= (uint) strlen(dbname);
  
  rw_wrlock(&LOCK_dboptions);
  if (!(opt= (my_dbopt_t*) hash_search(&dboptions, (byte*) dbname, length)))
  { 
    /* Options are not in the hash, insert them */
    char *tmp_name;
    if (!my_multi_malloc(MYF(MY_WME | MY_ZEROFILL),
                         &opt, (uint) sizeof(*opt), &tmp_name, length+1,
                         NullS))
    {
      error= 1;
      goto end;
    }
    
    opt->name= tmp_name;
    strmov(opt->name, dbname);
    opt->name_length= length;
    
    if ((error= my_hash_insert(&dboptions, (byte*) opt)))
    {
      my_free((gptr) opt, MYF(0));
      goto end;
    }
  }

  /* Update / write options in hash */
  opt->charset= create->default_table_charset;

end:
  rw_unlock(&LOCK_dboptions);  
  DBUG_RETURN(error);
}


/*
  Deletes database options from the hash.
*/

void del_dbopt(const char *path)
{
  my_dbopt_t *opt;
  rw_wrlock(&LOCK_dboptions);
  if ((opt= (my_dbopt_t *)hash_search(&dboptions, (const byte*) path,
                                      strlen(path))))
    hash_delete(&dboptions, (byte*) opt);
  rw_unlock(&LOCK_dboptions);
}


/* 
  Create database options file:

  DESCRIPTION
    Currently database default charset is only stored there.

  RETURN VALUES
  0	ok
  1	Could not create file or write to it.  Error sent through my_error()
*/

static bool write_db_opt(THD *thd, const char *path, HA_CREATE_INFO *create)
{
  register File file;
  char buf[256]; // Should be enough for one option
  bool error=1;

  if (!create->default_table_charset)
    create->default_table_charset= thd->variables.collation_server;
  
  if (put_dbopt(path, create))
    return 1;
  
  if ((file=my_create(path, CREATE_MODE,O_RDWR | O_TRUNC,MYF(MY_WME))) >= 0)
  {
    ulong length;
    length= (ulong) (strxnmov(buf, sizeof(buf), "default-character-set=",
                              create->default_table_charset->csname,
                              "\ndefault-collation=",
                              create->default_table_charset->name,
                              "\n", NullS) - buf);

    /* Error is written by my_write */
    if (!my_write(file,(byte*) buf, length, MYF(MY_NABP+MY_WME)))
      error=0;
    my_close(file,MYF(0));
  }
  return error;
}


/* 
  Load database options file

  load_db_opt()
  path		Path for option file
  create	Where to store the read options

  DESCRIPTION
    For now, only default-character-set is read.

  RETURN VALUES
  0	File found
  1	No database file or could not open it

*/

bool load_db_opt(THD *thd, const char *path, HA_CREATE_INFO *create)
{
  File file;
  char buf[256];
  DBUG_ENTER("load_db_opt");
  bool error=1;
  uint nbytes;

  bzero((char*) create,sizeof(*create));
  create->default_table_charset= thd->variables.collation_server;
  
  /* Check if options for this database are already in the hash */
  if (!get_dbopt(path, create))
    DBUG_RETURN(0);	   
  
  /* Otherwise, load options from the .opt file */
  if ((file=my_open(path, O_RDONLY | O_SHARE, MYF(0))) >= 0)
  {
    IO_CACHE cache;
    init_io_cache(&cache, file, IO_SIZE, READ_CACHE, 0, 0, MYF(0));

    while ((int) (nbytes= my_b_gets(&cache, (char*) buf, sizeof(buf))) > 0)
    {
      char *pos= buf+nbytes-1;
      /* Remove end space and control characters */
      while (pos > buf && !my_isgraph(&my_charset_latin1, pos[-1]))
	pos--;
      *pos=0;
      if ((pos= strchr(buf, '=')))
      {
	if (!strncmp(buf,"default-character-set", (pos-buf)))
	{
          /*
             Try character set name, and if it fails 
             try collation name, probably it's an old
             4.1.0 db.opt file, which didn't have
             separate default-character-set and
             default-collation commands.
          */
	  if (!(create->default_table_charset=
		get_charset_by_csname(pos+1, MY_CS_PRIMARY, MYF(0))) &&
              !(create->default_table_charset=
                get_charset_by_name(pos+1, MYF(0))))
	  {
	    sql_print_error("Error while loading database options: '%s':",path);
	    sql_print_error(ER(ER_UNKNOWN_CHARACTER_SET),pos+1);
            create->default_table_charset= default_charset_info;
	  }
	}
	else if (!strncmp(buf,"default-collation", (pos-buf)))
	{
	  if (!(create->default_table_charset= get_charset_by_name(pos+1,
								   MYF(0))))
	  {
	    sql_print_error("Error while loading database options: '%s':",path);
	    sql_print_error(ER(ER_UNKNOWN_COLLATION),pos+1);
            create->default_table_charset= default_charset_info;
	  }
	}
      }
    }
    end_io_cache(&cache);
    my_close(file,MYF(0));
    /*
      Put the loaded value into the hash.
      Note that another thread could've added the same
      entry to the hash after we called get_dbopt(),
      but it's not an error, as put_dbopt() takes this
      possibility into account.
    */
    error= put_dbopt(path, create);
  }
  DBUG_RETURN(error);
}


/*
  Create a database

  SYNOPSIS
  mysql_create_db()
  thd		Thread handler
  db		Name of database to create
		Function assumes that this is already validated.
  create_info	Database create options (like character set)
  silent	Used by replication when internally creating a database.
		In this case the entry should not be logged.

  RETURN VALUES
  0	ok
  -1	Error

*/

int mysql_create_db(THD *thd, char *db, HA_CREATE_INFO *create_info,
		    bool silent)
{
  char	 path[FN_REFLEN+16];
  long result= 1;
  int error= 0;
  MY_STAT stat_info;
  uint create_options= create_info ? create_info->options : 0;
  uint path_len;
  DBUG_ENTER("mysql_create_db");
  
  VOID(pthread_mutex_lock(&LOCK_mysql_create_db));

  // do not create database if another thread is holding read lock
  if (wait_if_global_read_lock(thd, 0, 1))
  {
    error= -1;
    goto exit2;
  }

  /* Check directory */
  strxmov(path, mysql_data_home, "/", db, NullS);
  path_len= unpack_dirname(path,path);    // Convert if not unix
  path[path_len-1]= 0;                    // Remove last '/' from path

  if (my_stat(path,&stat_info,MYF(0)))
  {
   if (!(create_options & HA_LEX_CREATE_IF_NOT_EXISTS))
    {
      my_error(ER_DB_CREATE_EXISTS,MYF(0),db);
      error= -1;
      goto exit;
    }
    result= 0;
  }
  else
  {
    if (my_errno != ENOENT)
    {
      my_error(EE_STAT, MYF(0),path,my_errno);
      goto exit;
    }
    if (my_mkdir(path,0777,MYF(0)) < 0)
    {
      my_error(ER_CANT_CREATE_DB,MYF(0),db,my_errno);
      error= -1;
      goto exit;
    }
  }

  path[path_len-1]= FN_LIBCHAR;
  strmake(path+path_len, MY_DB_OPT_FILE, sizeof(path)-path_len-1);
  if (write_db_opt(thd, path, create_info))
  {
    /*
      Could not create options file.
      Restore things to beginning.
    */
    path[path_len]= 0;
    if (rmdir(path) >= 0)
    {
      error= -1;
      goto exit;
    }
    /*
      We come here when we managed to create the database, but not the option
      file.  In this case it's best to just continue as if nothing has
      happened.  (This is a very unlikely senario)
    */
  }
  
  if (!silent)
  {
    char *query;
    uint query_length;

    if (!thd->query)				// Only in replication
    {
      query= 	     path;
      query_length= (uint) (strxmov(path,"create database `", db, "`", NullS) -
			    path);
    }
    else
    {
      query= 	    thd->query;
      query_length= thd->query_length;
    }
    mysql_update_log.write(thd, query, query_length);
    if (mysql_bin_log.is_open())
    {
      Query_log_event qinfo(thd, query, query_length, 0);
      mysql_bin_log.write(&qinfo);
    }
    send_ok(thd, result);
  }

exit:
  start_waiting_global_read_lock(thd);
exit2:
  VOID(pthread_mutex_unlock(&LOCK_mysql_create_db));
  DBUG_RETURN(error);
}


/* db-name is already validated when we come here */

int mysql_alter_db(THD *thd, const char *db, HA_CREATE_INFO *create_info)
{
  char path[FN_REFLEN+16];
  long result=1;
  int error= 0;
  DBUG_ENTER("mysql_alter_db");

  VOID(pthread_mutex_lock(&LOCK_mysql_create_db));

  // do not alter database if another thread is holding read lock
  if ((error=wait_if_global_read_lock(thd,0,1)))
    goto exit2;

  /* Check directory */
  strxmov(path, mysql_data_home, "/", db, "/", MY_DB_OPT_FILE, NullS);
  fn_format(path, path, "", "", MYF(MY_UNPACK_FILENAME));
  if ((error=write_db_opt(thd, path, create_info)))
    goto exit;

  /* 
     Change options if current database is being altered
     TODO: Delete this code
  */
  if (thd->db && !strcmp(thd->db,db))
  {
    thd->db_charset= (create_info && create_info->default_table_charset) ?
		     create_info->default_table_charset : 
		     thd->variables.collation_server;
    thd->variables.collation_database= thd->db_charset;
  }

  mysql_update_log.write(thd,thd->query, thd->query_length);
  if (mysql_bin_log.is_open())
  {
    Query_log_event qinfo(thd, thd->query, thd->query_length, 0);
    thd->clear_error();
    mysql_bin_log.write(&qinfo);
  }
  send_ok(thd, result);

exit:
  start_waiting_global_read_lock(thd);
exit2:
  VOID(pthread_mutex_unlock(&LOCK_mysql_create_db));
  DBUG_RETURN(error ? -1 : 0); /* -1 to delegate send_error() */
}


/*
  Drop all tables in a database and the database itself

  SYNOPSIS
    mysql_rm_db()
    thd			Thread handle
    db			Database name in the case given by user
		        It's already validated when we come here
    if_exists		Don't give error if database doesn't exists
    silent		Don't generate errors

  RETURN
    0   ok (Database dropped)
    -1	Error generated
*/


int mysql_rm_db(THD *thd,char *db,bool if_exists, bool silent)
{
  long deleted=0;
  int error= 0;
  char	path[FN_REFLEN+16], tmp_db[NAME_LEN+1];
  MY_DIR *dirp;
  uint length;
  DBUG_ENTER("mysql_rm_db");

  VOID(pthread_mutex_lock(&LOCK_mysql_create_db));

  // do not drop database if another thread is holding read lock
  if (wait_if_global_read_lock(thd, 0, 1))
  {
    error= -1;
    goto exit2;
  }

  (void) sprintf(path,"%s/%s",mysql_data_home,db);
  length= unpack_dirname(path,path);		// Convert if not unix
  strmov(path+length, MY_DB_OPT_FILE);		// Append db option file name
  del_dbopt(path);				// Remove dboption hash entry
  path[length]= '\0';				// Remove file name

  /* See if the directory exists */
  if (!(dirp= my_dir(path,MYF(MY_DONT_SORT))))
  {
    if (!if_exists)
    {
      error= -1;
      my_error(ER_DB_DROP_EXISTS,MYF(0),db);
      goto exit;
    }
    else
      push_warning_printf(thd, MYSQL_ERROR::WARN_LEVEL_NOTE,
			  ER_DB_DROP_EXISTS, ER(ER_DB_DROP_EXISTS), db);
  }
  else
  {
    pthread_mutex_lock(&LOCK_open);
    remove_db_from_cache(db);
    pthread_mutex_unlock(&LOCK_open);
    
    error= -1;
    if ((deleted= mysql_rm_known_files(thd, dirp, db, path, 0)) >= 0)
    {
      ha_drop_database(path);
      query_cache_invalidate1(db);  
      error = 0;
    }
  }
  if (lower_case_table_names)
  {
    /* Convert database to lower case */
    strmov(tmp_db, db);
    my_casedn_str(files_charset_info, tmp_db);
    db= tmp_db;
  }
  if (!silent && deleted>=0 && thd)
  {
    const char *query;
    ulong query_length;
    if (!thd->query)
    {
      /* The client used the old obsolete mysql_drop_db() call */
      query= path;
      query_length= (uint) (strxmov(path, "drop database `", db, "`",
                                     NullS) - path);
    }
    else
    {
      query =thd->query;
      query_length= thd->query_length;
    }
    mysql_update_log.write(thd, query, query_length);
    if (mysql_bin_log.is_open())
    {
      Query_log_event qinfo(thd, query, query_length, 0);
      thd->clear_error();
      mysql_bin_log.write(&qinfo);
    }
    send_ok(thd, (ulong) deleted);
  }

exit:
  start_waiting_global_read_lock(thd);
  /*
    If this database was the client's selected database, we silently change the
    client's selected database to nothing (to have an empty SELECT DATABASE()
    in the future). For this we free() thd->db and set it to 0. But we don't do
    free() for the slave thread. Indeed, doing a x_free() on it leads to nasty
    problems (i.e. long painful debugging) because in this thread, thd->db is
    the same as data_buf and db of the Query_log_event which is dropping the
    database. So if you free() thd->db, you're freeing data_buf. You set
    thd->db to 0 but not data_buf (thd->db and data_buf are two distinct
    pointers which point to the same place). Then in ~Query_log_event(), we
    have 'if (data_buf) free(data_buf)' data_buf is !=0 so this makes a
    DOUBLE free().
    Side effects of this double free() are, randomly (depends on the machine),
    when the slave is replicating a DROP DATABASE: 
    - garbage characters in the error message:
    "Error 'Can't drop database 'test2'; database doesn't exist' on query
    'h4zI<7A><49>'"
    - segfault
    - hang in "free(vio)" (yes!) in the I/O or SQL slave threads (so slave
    server hangs at shutdown etc).
  */
  if (thd->db && !strcmp(thd->db, db))
  {
    if (!(thd->slave_thread)) /* a slave thread will free it itself */
      x_free(thd->db);
    thd->db= 0;
    thd->db_length= 0;
  }
exit2:
  VOID(pthread_mutex_unlock(&LOCK_mysql_create_db));

  DBUG_RETURN(error);
}

/*
  Removes files with known extensions plus all found subdirectories that
  are 2 hex digits (raid directories).
  thd MUST be set when calling this function!
*/

static long mysql_rm_known_files(THD *thd, MY_DIR *dirp, const char *db,
				 const char *org_path, uint level)
{
  long deleted=0;
  ulong found_other_files=0;
  char filePath[FN_REFLEN];
  TABLE_LIST *tot_list=0, **tot_list_next;
  List<String> raid_dirs;
  DBUG_ENTER("mysql_rm_known_files");
  DBUG_PRINT("enter",("path: %s", org_path));

  tot_list_next= &tot_list;

  for (uint idx=0 ;
       idx < (uint) dirp->number_off_files && !thd->killed ;
       idx++)
  {
    FILEINFO *file=dirp->dir_entry+idx;
    char *extension;
    DBUG_PRINT("info",("Examining: %s", file->name));

    /* skiping . and .. */
    if (file->name[0] == '.' && (!file->name[1] ||
       (file->name[1] == '.' &&  !file->name[2])))
      continue;

    /* Check if file is a raid directory */
    if ((my_isdigit(&my_charset_latin1, file->name[0]) ||
	 (file->name[0] >= 'a' && file->name[0] <= 'f')) &&
	(my_isdigit(&my_charset_latin1, file->name[1]) ||
	 (file->name[1] >= 'a' && file->name[1] <= 'f')) &&
	!file->name[2] && !level)
    {
      char newpath[FN_REFLEN], *copy_of_path;
      MY_DIR *new_dirp;
      String *dir;
      uint length;

      strxmov(newpath,org_path,"/",file->name,NullS);
      length= unpack_filename(newpath,newpath);
      if ((new_dirp = my_dir(newpath,MYF(MY_DONT_SORT))))
      {
	DBUG_PRINT("my",("New subdir found: %s", newpath));
	if ((mysql_rm_known_files(thd, new_dirp, NullS, newpath,1)) < 0)
	  goto err;
	if (!(copy_of_path= thd->memdup(newpath, length+1)) ||
	    !(dir= new (thd->mem_root) String(copy_of_path, length,
					       &my_charset_bin)) ||
	    raid_dirs.push_back(dir))
	  goto err;
	continue;
      }
      found_other_files++;
      continue;
    }
    extension= fn_ext(file->name);
    if (find_type(extension, &deletable_extentions,1+2) <= 0)
    {
      if (find_type(extension, ha_known_exts(),1+2) <= 0)
	found_other_files++;
      continue;
    }
    // just for safety we use files_charset_info
    if (db && !my_strcasecmp(files_charset_info,
                             extension, reg_ext))
    {
      /* Drop the table nicely */
      *extension= 0;			// Remove extension
      TABLE_LIST *table_list=(TABLE_LIST*)
	thd->calloc(sizeof(*table_list)+ strlen(db)+strlen(file->name)+2);
      if (!table_list)
	goto err;
      table_list->db= (char*) (table_list+1);
      strmov(table_list->real_name= strmov(table_list->db,db)+1, file->name);
      table_list->alias= table_list->real_name;	// If lower_case_table_names=2
      /* Link into list */
      (*tot_list_next)= table_list;
      tot_list_next= &table_list->next;
      deleted++;
    }
    else
    {
      strxmov(filePath, org_path, "/", file->name, NullS);
      if (my_delete_with_symlink(filePath,MYF(MY_WME)))
      {
	goto err;
      }
    }
  }
  if (thd->killed ||
      (tot_list && mysql_rm_table_part2_with_lock(thd, tot_list, 1, 0, 1)))
    goto err;

  /* Remove RAID directories */
  {
    List_iterator<String> it(raid_dirs);
    String *dir;
    while ((dir= it++))
      if (rmdir(dir->c_ptr()) < 0)
	found_other_files++;
  }
  my_dirend(dirp);  
  
  /*
    If the directory is a symbolic link, remove the link first, then
    remove the directory the symbolic link pointed at
  */
  if (found_other_files)
  {
    my_error(ER_DB_DROP_RMDIR, MYF(0), org_path, EEXIST);
    DBUG_RETURN(-1);
  }
  else
  {
    char tmp_path[FN_REFLEN], *pos;
    char *path= tmp_path;
    unpack_filename(tmp_path,org_path);
#ifdef HAVE_READLINK
    int error;
    
    /* Remove end FN_LIBCHAR as this causes problem on Linux in readlink */
    pos=strend(path);
    if (pos > path && pos[-1] == FN_LIBCHAR)
      *--pos=0;

    if ((error=my_readlink(filePath, path, MYF(MY_WME))) < 0)
      DBUG_RETURN(-1);
    if (!error)
    {
      if (my_delete(path,MYF(!level ? MY_WME : 0)))
      {
	/* Don't give errors if we can't delete 'RAID' directory */
	if (level)
	  DBUG_RETURN(deleted);
	DBUG_RETURN(-1);
      }
      /* Delete directory symbolic link pointed at */
      path= filePath;
    }
#endif
    /* Remove last FN_LIBCHAR to not cause a problem on OS/2 */
    pos=strend(path);

    if (pos > path && pos[-1] == FN_LIBCHAR)
      *--pos=0;
    /* Don't give errors if we can't delete 'RAID' directory */
    if (rmdir(path) < 0 && !level)
    {
      my_error(ER_DB_DROP_RMDIR, MYF(0), path, errno);
      DBUG_RETURN(-1);
    }
  }
  DBUG_RETURN(deleted);

err:
  my_dirend(dirp);
  DBUG_RETURN(-1);
}


/*
  Change default database.

  SYNOPSIS
    mysql_change_db()
    thd		Thread handler
    name	Databasename

  DESCRIPTION
    Becasue the database name may have been given directly from the
    communication packet (in case of 'connect' or 'COM_INIT_DB')
    we have to do end space removal in this function.

  NOTES
    Do as little as possible in this function, as it is not called for the
    replication slave SQL thread (for that thread, setting of thd->db is done
    in ::exec_event() methods of log_event.cc).

  RETURN VALUES
    0	ok
    1	error
*/

bool mysql_change_db(THD *thd, const char *name)
{
  int length, db_length;
  char *dbname=my_strdup((char*) name,MYF(MY_WME));
  char	path[FN_REFLEN];
  HA_CREATE_INFO create;
#ifndef NO_EMBEDDED_ACCESS_CHECKS
  ulong db_access;
#endif
  DBUG_ENTER("mysql_change_db");

  if (!dbname || !(db_length= strlen(dbname)))
  {
    x_free(dbname);				/* purecov: inspected */
    send_error(thd,ER_NO_DB_ERROR);	/* purecov: inspected */
    DBUG_RETURN(1);				/* purecov: inspected */
  }
  if (check_db_name(dbname))
  {
    net_printf(thd, ER_WRONG_DB_NAME, dbname);
    x_free(dbname);
    DBUG_RETURN(1);
  }
  DBUG_PRINT("info",("Use database: %s", dbname));
#ifndef NO_EMBEDDED_ACCESS_CHECKS
  if (test_all_bits(thd->master_access,DB_ACLS))
    db_access=DB_ACLS;
  else
    db_access= (acl_get(thd->host,thd->ip, thd->priv_user,dbname,0) |
		thd->master_access);
  if (!(db_access & DB_ACLS) && (!grant_option || check_grant_db(thd,dbname)))
  {
    net_printf(thd,ER_DBACCESS_DENIED_ERROR,
	       thd->priv_user,
	       thd->priv_host,
	       dbname);
    mysql_log.write(thd,COM_INIT_DB,ER(ER_DBACCESS_DENIED_ERROR),
		    thd->priv_user,
		    thd->priv_host,
		    dbname);
    my_free(dbname,MYF(0));
    DBUG_RETURN(1);
  }
#endif
  (void) sprintf(path,"%s/%s",mysql_data_home,dbname);
  length=unpack_dirname(path,path);		// Convert if not unix
  if (length && path[length-1] == FN_LIBCHAR)
    path[length-1]=0;				// remove ending '\'
  if (access(path,F_OK))
  {
    net_printf(thd,ER_BAD_DB_ERROR,dbname);
    my_free(dbname,MYF(0));
    DBUG_RETURN(1);
  }
  send_ok(thd);
  x_free(thd->db);
  thd->db=dbname;				// THD::~THD will free this
  thd->db_length=db_length;
#ifndef NO_EMBEDDED_ACCESS_CHECKS
  thd->db_access=db_access;
#endif
  strmov(path+unpack_dirname(path,path), MY_DB_OPT_FILE);
  load_db_opt(thd, path, &create);
  thd->db_charset= create.default_table_charset ?
		   create.default_table_charset :
		   thd->variables.collation_server;
  thd->variables.collation_database= thd->db_charset;
  DBUG_RETURN(0);
}