Drizzled Public API Documentation

mi_rkey.cc
1 /* Copyright (C) 2000-2006 MySQL AB
2 
3  This program is free software; you can redistribute it and/or modify
4  it under the terms of the GNU General Public License as published by
5  the Free Software Foundation; version 2 of the License.
6 
7  This program is distributed in the hope that it will be useful,
8  but WITHOUT ANY WARRANTY; without even the implied warranty of
9  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
10  GNU General Public License for more details.
11 
12  You should have received a copy of the GNU General Public License
13  along with this program; if not, write to the Free Software
14  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
15 
16 /* Read record based on a key */
17 
18 #include "myisam_priv.h"
19 
20 using namespace drizzled;
21 
22  /* Read a record using key */
23  /* Ordinary search_flag is 0 ; Give error if no record with key */
24 
25 int mi_rkey(MI_INFO *info, unsigned char *buf, int inx, const unsigned char *key,
26  key_part_map keypart_map, enum ha_rkey_function search_flag)
27 {
28  unsigned char *key_buff;
29  MYISAM_SHARE *share=info->s;
30  MI_KEYDEF *keyinfo;
31  HA_KEYSEG *last_used_keyseg;
32  uint32_t pack_key_length, use_key_length, nextflag;
33  uint32_t myisam_search_flag;
34  int res= 0;
35 
36  if ((inx = _mi_check_index(info,inx)) < 0)
37  return(errno);
38 
39  info->update&= (HA_STATE_CHANGED | HA_STATE_ROW_CHANGED);
40  info->last_key_func= search_flag;
41  keyinfo= share->keyinfo + inx;
42 
43  if (info->once_flags & USE_PACKED_KEYS)
44  {
45  info->once_flags&= ~USE_PACKED_KEYS; /* Reset flag */
46  /*
47  key is already packed!; This happens when we are using a MERGE TABLE
48  In this key 'key_part_map' is the length of the key !
49  */
50  key_buff=info->lastkey+info->s->base.max_key_length;
51  pack_key_length= keypart_map;
52  memmove(key_buff, key, pack_key_length);
53  last_used_keyseg= info->s->keyinfo[inx].seg + info->last_used_keyseg;
54  }
55  else
56  {
57  assert(keypart_map);
58  /* Save the packed key for later use in the second buffer of lastkey. */
59  key_buff=info->lastkey+info->s->base.max_key_length;
60  pack_key_length=_mi_pack_key(info,(uint) inx, key_buff, (unsigned char*) key,
61  keypart_map, &last_used_keyseg);
62  /* Save packed_key_length for use by the MERGE engine. */
63  info->pack_key_length= pack_key_length;
64  info->last_used_keyseg= (uint16_t) (last_used_keyseg -
65  info->s->keyinfo[inx].seg);
66  }
67 
68  if (fast_mi_readinfo(info))
69  goto err;
70 
71  nextflag=myisam_read_vec[search_flag];
72  use_key_length=pack_key_length;
73  if (!(nextflag & (SEARCH_FIND | SEARCH_NO_FIND | SEARCH_LAST)))
74  use_key_length=USE_WHOLE_KEY;
75 
76  switch (info->s->keyinfo[inx].key_alg) {
77  case HA_KEY_ALG_BTREE:
78  default:
79  myisam_search_flag= myisam_read_vec[search_flag];
80  if (!_mi_search(info, keyinfo, key_buff, use_key_length,
81  myisam_search_flag, info->s->state.key_root[inx]))
82  {
83  /*
84  Found a key, but it might not be usable. We cannot use rows that
85  are inserted by other threads after we got our table lock
86  ("concurrent inserts"). The record may not even be present yet.
87  Keys are inserted into the index(es) before the record is
88  inserted into the data file. When we got our table lock, we
89  saved the current data_file_length. Concurrent inserts always go
90  to the end of the file. So we can test if the found key
91  references a new record.
92 
93  If we are searching for a partial key (or using >, >=, < or <=) and
94  the data is outside of the data file, we need to continue searching
95  for the first key inside the data file.
96 
97  We do also continue searching if an index condition check function
98  is available.
99  */
100  while ((info->lastpos >= info->state->data_file_length &&
101  (search_flag != HA_READ_KEY_EXACT ||
102  last_used_keyseg != keyinfo->seg + keyinfo->keysegs)) ||
103  (info->index_cond_func &&
104  !(res= mi_check_index_cond(info, inx, buf))))
105  {
106  uint32_t not_used[2];
107  /*
108  Skip rows that are inserted by other threads since we got a lock
109  Note that this can only happen if we are not searching after an
110  full length exact key, because the keys are sorted
111  according to position
112  */
113  if (_mi_search_next(info, keyinfo, info->lastkey,
114  info->lastkey_length,
115  myisam_readnext_vec[search_flag],
116  info->s->state.key_root[inx]))
117  break;
118  /*
119  Check that the found key does still match the search.
120  _mi_search_next() delivers the next key regardless of its
121  value.
122  */
123  if (search_flag == HA_READ_KEY_EXACT &&
124  ha_key_cmp(keyinfo->seg, key_buff, info->lastkey, use_key_length,
125  SEARCH_FIND, not_used))
126  {
127  errno= HA_ERR_KEY_NOT_FOUND;
128  info->lastpos= HA_OFFSET_ERROR;
129  break;
130  }
131  }
132  if (res == 2)
133  {
134  info->lastpos= HA_OFFSET_ERROR;
135  return((errno= HA_ERR_KEY_NOT_FOUND));
136  }
137  /*
138  Error if no row found within the data file. (Bug #29838)
139  Do not overwrite errno if already at HA_OFFSET_ERROR.
140  */
141  if (info->lastpos != HA_OFFSET_ERROR &&
142  info->lastpos >= info->state->data_file_length)
143  {
144  info->lastpos= HA_OFFSET_ERROR;
145  errno= HA_ERR_KEY_NOT_FOUND;
146  }
147  }
148  }
149 
150  /* Calculate length of the found key; Used by mi_rnext_same */
151  if ((keyinfo->flag & HA_VAR_LENGTH_KEY) && last_used_keyseg &&
152  info->lastpos != HA_OFFSET_ERROR)
153  info->last_rkey_length= _mi_keylength_part(keyinfo, info->lastkey,
154  last_used_keyseg);
155  else
156  info->last_rkey_length= pack_key_length;
157 
158  /* Check if we don't want to have record back, only error message */
159  if (!buf)
160  return(info->lastpos == HA_OFFSET_ERROR ? errno : 0);
161 
162  if (!(*info->read_record)(info,info->lastpos,buf))
163  {
164  info->update|= HA_STATE_AKTIV; /* Record is read */
165  return(0);
166  }
167 
168  info->lastpos = HA_OFFSET_ERROR; /* Didn't find key */
169 
170  /* Store last used key as a base for read next */
171  memcpy(info->lastkey,key_buff,pack_key_length);
172  info->last_rkey_length= pack_key_length;
173  memset(info->lastkey+pack_key_length, 0, info->s->base.rec_reflength);
174  info->lastkey_length=pack_key_length+info->s->base.rec_reflength;
175 
176  if (search_flag == HA_READ_AFTER_KEY)
177  info->update|=HA_STATE_NEXT_FOUND; /* Previous gives last row */
178 err:
179  return(errno);
180 } /* _mi_rkey */
TODO: Rename this file - func.h is stupid.