~drizzle-trunk/drizzle/development

/* Copyright (C) 2000-2006 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., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA */

/* Read record based on a key */

#include "myisam_priv.h"

using namespace drizzled;

	/* Read a record using key */

	/* Ordinary search_flag is 0 ; Give error if no record with key */

int mi_rkey(MI_INFO *info, unsigned char *buf, int inx, const unsigned char *key,

            key_part_map keypart_map, enum ha_rkey_function search_flag)

{

  unsigned char *key_buff;

  MYISAM_SHARE *share=info->s;

  MI_KEYDEF *keyinfo;

  HA_KEYSEG *last_used_keyseg;

  uint32_t pack_key_length, use_key_length, nextflag;

  uint32_t myisam_search_flag;

  int res= 0;

  if ((inx = _mi_check_index(info,inx)) < 0)

    return(errno);

  info->update&= (HA_STATE_CHANGED | HA_STATE_ROW_CHANGED);

  info->last_key_func= search_flag;

  keyinfo= share->keyinfo + inx;

  if (info->once_flags & USE_PACKED_KEYS)

  {

    info->once_flags&= ~USE_PACKED_KEYS;	/* Reset flag */

    /*

      key is already packed!;  This happens when we are using a MERGE TABLE

      In this key 'key_part_map' is the length of the key !

    */

    key_buff=info->lastkey+info->s->base.max_key_length;

    pack_key_length= keypart_map;

    memmove(key_buff, key, pack_key_length);

    last_used_keyseg= info->s->keyinfo[inx].seg + info->last_used_keyseg;

  }

  else

  {

    assert(keypart_map);

    /* Save the packed key for later use in the second buffer of lastkey. */

    key_buff=info->lastkey+info->s->base.max_key_length;

    pack_key_length=_mi_pack_key(info,(uint) inx, key_buff, (unsigned char*) key,

				 keypart_map, &last_used_keyseg);

    /* Save packed_key_length for use by the MERGE engine. */

    info->pack_key_length= pack_key_length;

    info->last_used_keyseg= (uint16_t) (last_used_keyseg -

                                      info->s->keyinfo[inx].seg);

  }

  if (fast_mi_readinfo(info))

    goto err;

  nextflag=myisam_read_vec[search_flag];

  use_key_length=pack_key_length;

  if (!(nextflag & (SEARCH_FIND | SEARCH_NO_FIND | SEARCH_LAST)))

    use_key_length=USE_WHOLE_KEY;

  switch (info->s->keyinfo[inx].key_alg) {

  case HA_KEY_ALG_BTREE:

  default:

    myisam_search_flag= myisam_read_vec[search_flag];

    if (!_mi_search(info, keyinfo, key_buff, use_key_length,

                    myisam_search_flag, info->s->state.key_root[inx]))

    {

      /*

        Found a key, but it might not be usable. We cannot use rows that

        are inserted by other threads after we got our table lock

        ("concurrent inserts"). The record may not even be present yet.

        Keys are inserted into the index(es) before the record is

        inserted into the data file. When we got our table lock, we

        saved the current data_file_length. Concurrent inserts always go

        to the end of the file. So we can test if the found key

        references a new record.

        If we are searching for a partial key (or using >, >=, < or <=) and

        the data is outside of the data file, we need to continue searching

        for the first key inside the data file.

        We do also continue searching if an index condition check function

        is available.

      */

      while ((info->lastpos >= info->state->data_file_length &&

              (search_flag != HA_READ_KEY_EXACT ||

              last_used_keyseg != keyinfo->seg + keyinfo->keysegs)) ||

             (info->index_cond_func &&

              !(res= mi_check_index_cond(info, inx, buf))))

      {

        uint32_t not_used[2];

        /*

          Skip rows that are inserted by other threads since we got a lock

          Note that this can only happen if we are not searching after an

          full length exact key, because the keys are sorted

          according to position

        */

        if  (_mi_search_next(info, keyinfo, info->lastkey,

                             info->lastkey_length,

                             myisam_readnext_vec[search_flag],

                             info->s->state.key_root[inx]))

          break;

        /*

          Check that the found key does still match the search.

          _mi_search_next() delivers the next key regardless of its

          value.

        */

        if (search_flag == HA_READ_KEY_EXACT &&

            ha_key_cmp(keyinfo->seg, key_buff, info->lastkey, use_key_length,

                       SEARCH_FIND, not_used))

        {

          errno= HA_ERR_KEY_NOT_FOUND;

          info->lastpos= HA_OFFSET_ERROR;

          break;

        }

      }

      if (res == 2)

      {

        info->lastpos= HA_OFFSET_ERROR;

        return((errno= HA_ERR_KEY_NOT_FOUND));

      }

      /*

        Error if no row found within the data file. (Bug #29838)

        Do not overwrite errno if already at HA_OFFSET_ERROR.

      */

      if (info->lastpos != HA_OFFSET_ERROR &&

          info->lastpos >= info->state->data_file_length)

      {

        info->lastpos= HA_OFFSET_ERROR;

        errno= HA_ERR_KEY_NOT_FOUND;

      }

    }

  }

  /* Calculate length of the found key;  Used by mi_rnext_same */

  if ((keyinfo->flag & HA_VAR_LENGTH_KEY) && last_used_keyseg &&

      info->lastpos != HA_OFFSET_ERROR)

    info->last_rkey_length= _mi_keylength_part(keyinfo, info->lastkey,

					       last_used_keyseg);

  else

    info->last_rkey_length= pack_key_length;

  /* Check if we don't want to have record back, only error message */

  if (!buf)

    return(info->lastpos == HA_OFFSET_ERROR ? errno : 0);

  if (!(*info->read_record)(info,info->lastpos,buf))

  {

    info->update|= HA_STATE_AKTIV;		/* Record is read */

    return(0);

  }

  info->lastpos = HA_OFFSET_ERROR;		/* Didn't find key */

  /* Store last used key as a base for read next */

  memcpy(info->lastkey,key_buff,pack_key_length);

  info->last_rkey_length= pack_key_length;

  memset(info->lastkey+pack_key_length, 0, info->s->base.rec_reflength);

  info->lastkey_length=pack_key_length+info->s->base.rec_reflength;

  if (search_flag == HA_READ_AFTER_KEY)

    info->update|=HA_STATE_NEXT_FOUND;		/* Previous gives last row */

err:

  return(errno);

} /* _mi_rkey */