~drizzle-trunk/drizzle/development

/* Copyright (C) 2000-2002 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; version 2 of the License.

   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 */

#include "heapdef.h"

#include <string.h>

/* Read next record with the same key */

int heap_rnext(HP_INFO *info, unsigned char *record)

{

  unsigned char *pos;

  HP_SHARE *share=info->s;

  HP_KEYDEF *keyinfo;

  if (info->lastinx < 0)

    return(my_errno=HA_ERR_WRONG_INDEX);

  keyinfo = share->keydef + info->lastinx;

  if (keyinfo->algorithm == HA_KEY_ALG_BTREE)

  {

    heap_rb_param custom_arg;

    if (info->last_pos)

    {

      /*

        We enter this branch for non-DELETE queries after heap_rkey()

        or heap_rfirst(). As last key position (info->last_pos) is available,

        we only need to climb the tree using tree_search_next().

      */

      pos = (unsigned char *)tree_search_next(&keyinfo->rb_tree,

                                              &info->last_pos,

                                              offsetof(TREE_ELEMENT, left),

                                              offsetof(TREE_ELEMENT, right));

    }

    else if (!info->lastkey_len)

    {

      /*

        We enter this branch only for DELETE queries after heap_rfirst(). E.g.

        DELETE FROM t1 WHERE a<10. As last key position is not available

        (last key is removed by heap_delete()), we must restart search as it

        is done in heap_rfirst().

        It should be safe to handle this situation without this branch. That is

        branch below should find smallest element in a tree as lastkey_len is

        zero. tree_search_edge() is a kind of optimisation here as it should be

        faster than tree_search_key().

      */

      pos= (unsigned char *)tree_search_edge(&keyinfo->rb_tree, info->parents,

                                             &info->last_pos,

                                             offsetof(TREE_ELEMENT, left));

    }

    else

    {

      /*

        We enter this branch only for DELETE queries after heap_rkey(). E.g.

        DELETE FROM t1 WHERE a=10. As last key position is not available

        (last key is removed by heap_delete()), we must restart search as it

        is done in heap_rkey().

      */

      custom_arg.keyseg = keyinfo->seg;

      custom_arg.key_length = info->lastkey_len;

      custom_arg.search_flag = SEARCH_SAME | SEARCH_FIND;

      pos = (unsigned char *)tree_search_key(&keyinfo->rb_tree,

                                             info->lastkey, info->parents,

                                             &info->last_pos,

                                             info->last_find_flag,

                                             &custom_arg);

    }

    if (pos)

    {

      memcpy(&pos, pos + (*keyinfo->get_key_length)(keyinfo, pos),

	     sizeof(unsigned char*));

      info->current_ptr = pos;

    }

    else

    {

      my_errno = HA_ERR_KEY_NOT_FOUND;

    }

  }

  else

  {

    if (info->current_hash_ptr)

      pos= hp_search_next(info, keyinfo, info->lastkey,

			   info->current_hash_ptr);

    else

    {

      if (!info->current_ptr && (info->update & HA_STATE_NEXT_FOUND))

      {

	pos=0;					/* Read next after last */

	my_errno=HA_ERR_KEY_NOT_FOUND;

      }

      else if (!info->current_ptr)		/* Deleted or first call */

	pos= hp_search(info, keyinfo, info->lastkey, 0);

      else

	pos= hp_search(info, keyinfo, info->lastkey, 1);

    }

  }

  if (!pos)

  {

    info->update=HA_STATE_NEXT_FOUND;		/* For heap_rprev */

    if (my_errno == HA_ERR_KEY_NOT_FOUND)

      my_errno=HA_ERR_END_OF_FILE;

    return(my_errno);

  }

  hp_extract_record(share, record, pos);

  info->update=HA_STATE_AKTIV | HA_STATE_NEXT_FOUND;

  return(0);

}