mi_rkey.c

/* Copyright (c) 2000, 2023, Oracle and/or its affiliates.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License, version 2.0,
   as published by the Free Software Foundation.

   This program is also distributed with certain software (including
   but not limited to OpenSSL) that is licensed under separate terms,
   as designated in a particular file or component or in included license
   documentation.  The authors of MySQL hereby grant you an additional
   permission to link the program and your derivative works with the
   separately licensed software that they have included with MySQL.

   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, version 2.0, 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 "myisamdef.h"
#include "rt_index.h"

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

int mi_rkey(MI_INFO *info, uchar *buf, int inx, const uchar *key,
            key_part_map keypart_map, enum ha_rkey_function search_flag)
{
  uchar *key_buff;
  MYISAM_SHARE *share=info->s;
  MI_KEYDEF *keyinfo;
  HA_KEYSEG *last_used_keyseg;
  uint pack_key_length, use_key_length, nextflag;
  uint myisam_search_flag;
  int res= 0;
  DBUG_ENTER("mi_rkey");
  DBUG_PRINT("enter", ("base: 0x%lx  buf: 0x%lx  inx: %d  search_flag: %d",
                       (long) info, (long) buf, inx, search_flag));

  if ((inx = _mi_check_index(info,inx)) < 0)
    DBUG_RETURN(my_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, (uchar*) 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) (last_used_keyseg -
                                      info->s->keyinfo[inx].seg);
    DBUG_EXECUTE("info",_mi_print_key(DBUG_FILE, keyinfo->seg,
				     key_buff, pack_key_length););
  }

  if (fast_mi_readinfo(info))
    goto err;

  if (share->concurrent_insert)
    mysql_rwlock_rdlock(&share->key_root_lock[inx]);

  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_RTREE:
    if (rtree_find_first(info,inx,key_buff,use_key_length,nextflag) < 0)
    {
      // rtree_find_first will return -1 for an empty index,
      // but it's not a crash.
      if (my_errno() != HA_ERR_END_OF_FILE || info->lastpos != HA_OFFSET_ERROR ||
          info->s->state.state.records != 0)
      {
        mi_print_error(info->s, HA_ERR_CRASHED);
        set_my_errno(HA_ERR_CRASHED);
      }
      if (share->concurrent_insert)
        mysql_rwlock_unlock(&share->key_root_lock[inx]);
      goto err;
    }
    break;
  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))))
      {
        uint 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))
        {
          set_my_errno(HA_ERR_KEY_NOT_FOUND);
          info->lastpos= HA_OFFSET_ERROR;
          break;
        }
      }
      if (res == 2)
      {
        info->lastpos= HA_OFFSET_ERROR;
        if (share->concurrent_insert)
          mysql_rwlock_unlock(&share->key_root_lock[inx]);
        set_my_errno(HA_ERR_KEY_NOT_FOUND);
        DBUG_RETURN(HA_ERR_KEY_NOT_FOUND);
      }
      /*
        Error if no row found within the data file. (Bug #29838)
        Do not overwrite my_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;
        set_my_errno(HA_ERR_KEY_NOT_FOUND);
      }
    }
  }
  if (share->concurrent_insert)
    mysql_rwlock_unlock(&share->key_root_lock[inx]);

  /* 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;

  /* Next call to mi_rnext_same should set rnext_same_key. */
  info->set_rnext_same_key= TRUE;

  /* Check if we don't want to have record back, only error message */
  if (!buf)
    DBUG_RETURN(info->lastpos == HA_OFFSET_ERROR ? my_errno() : 0);

  if (!(*info->read_record)(info,info->lastpos,buf))
  {
    info->update|= HA_STATE_AKTIV;		/* Record is read */
    DBUG_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:
  DBUG_RETURN(my_errno());
} /* _mi_rkey */