summaryrefslogtreecommitdiff
path: root/myisam/rt_split.c
blob: 005e86805bb9393940467890ff83f3afb0c0cd90 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
/* Copyright (C) 2000 MySQL AB & Alexey Botchkov & MySQL Finland AB 
   & TCX DataKonsult 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 */

#include "myisamdef.h"

#ifdef HAVE_RTREE_KEYS

#include "rt_index.h"
#include "rt_key.h"
#include "rt_mbr.h"

typedef struct
{
  double square;
  int n_node;
  uchar *key;
  double *coords;
} SplitStruct;

inline static double *reserve_coords(double **d_buffer, int n_dim)
{
  double *coords = *d_buffer;
  (*d_buffer) += n_dim * 2;
  return coords;
}

static void mbr_join(double *a, const double *b, int n_dim)
{
  double *end = a + n_dim * 2;
  do
  {
    if (a[0] > b[0])
      a[0] = b[0];

    if (a[1] < b[1])
      a[1] = b[1];

    a += 2;
    b += 2;
  }while (a != end);
}

/*
Counts the square of mbr which is a join of a and b
*/
static double mbr_join_square(const double *a, const double *b, int n_dim)
{
  const double *end = a + n_dim * 2;
  double square = 1.0;
  do
  {
    square *= 
      ((a[1] < b[1]) ? b[1] : a[1]) - ((a[0] > b[0]) ? b[0] : a[0]);

    a += 2;
    b += 2;
  }while (a != end);

  return square;
}

static double count_square(const double *a, int n_dim)
{
  const double *end = a + n_dim * 2;
  double square = 1.0;
  do
  {
    square *= a[1] - a[0];
    a += 2;
  }while (a != end);
  return square;
}

inline static void copy_coords(double *dst, const double *src, int n_dim)
{
  memcpy(dst, src, sizeof(double) * (n_dim * 2));
}

/* 
Select two nodes to collect group upon
*/
static void pick_seeds(SplitStruct *node, int n_entries, 
     SplitStruct **seed_a, SplitStruct **seed_b, int n_dim)
{
  SplitStruct *cur1;
  SplitStruct *lim1 = node + (n_entries - 1);
  SplitStruct *cur2;
  SplitStruct *lim2 = node + n_entries;

  double max_d = -DBL_MAX;
  double d;

  for (cur1 = node; cur1 < lim1; ++cur1)
  {
    for (cur2=cur1 + 1; cur2 < lim2; ++cur2)
    {
      
      d = mbr_join_square(cur1->coords, cur2->coords, n_dim) - cur1->square - 
          cur2->square;
      if (d > max_d)
      {
        max_d = d;
        *seed_a = cur1;
        *seed_b = cur2;
      }
    }
  }
}

/* 
Select next node and group where to add 
*/
static void pick_next(SplitStruct *node, int n_entries, double *g1, double *g2,
    SplitStruct **choice, int *n_group, int n_dim)
{
  SplitStruct *cur = node;
  SplitStruct *end = node + n_entries;

  double max_diff = -DBL_MAX;

  for (; cur<end; ++cur)
  {
    double diff;
    double abs_diff;

    if (cur->n_node)
    {
      continue;
    }

    diff = mbr_join_square(g1, cur->coords, n_dim) -
      mbr_join_square(g2, cur->coords, n_dim);

    abs_diff = fabs(diff);
    if (abs_diff  > max_diff)
    {
      max_diff = abs_diff;
      *n_group = 1 + (diff > 0);
      *choice = cur;
    }
  }
}

/*
Mark not-in-group entries as n_group
*/
static void mark_all_entries(SplitStruct *node, int n_entries, int n_group)
{
  SplitStruct *cur = node;
  SplitStruct *end = node + n_entries;
  for (; cur<end; ++cur)
  {
    if (cur->n_node)
    {
      continue;
    }
    cur->n_node = n_group;
  }
}

static int split_rtree_node(SplitStruct *node, int n_entries, 
                   int all_size, /* Total key's size */
                   int key_size,
                   int min_size, /* Minimal group size */
                   int size1, int size2 /* initial group sizes */,
                   double **d_buffer, int n_dim)
{
  SplitStruct *cur;
  SplitStruct *a;
  SplitStruct *b;
  double *g1 = reserve_coords(d_buffer, n_dim);
  double *g2 = reserve_coords(d_buffer, n_dim);
  SplitStruct *next;
  int next_node;
  int i;
  SplitStruct *end = node + n_entries;

  if (all_size < min_size * 2)
  {
    return 1;
  }

  cur = node;
  for (; cur<end; ++cur)
  {
    cur->square = count_square(cur->coords, n_dim);
    cur->n_node = 0;
  }

  pick_seeds(node, n_entries, &a, &b, n_dim);
  a->n_node = 1;
  b->n_node = 2;
  

  copy_coords(g1, a->coords, n_dim);
  size1 += key_size;
  copy_coords(g2, b->coords, n_dim);
  size2 += key_size;


  for (i=n_entries - 2; i>0; --i)
  {
    if (all_size - (size2 + key_size) < min_size) /* Can't write into group 2 */
    {
      mark_all_entries(node, n_entries, 1);
      break;
    }

    if (all_size - (size1 + key_size) < min_size) /* Can't write into group 1 */
    {
      mark_all_entries(node, n_entries, 2);
      break;
    }

    pick_next(node, n_entries, g1, g2, &next, &next_node, n_dim);
    if (next_node == 1)
    {
      size1 += key_size;
      mbr_join(g1, next->coords, n_dim);
    }
    else
    {
      size2 += key_size;
      mbr_join(g2, next->coords, n_dim);
    }
    next->n_node = next_node;
  }

  return 0;
}

int rtree_split_page(MI_INFO *info, MI_KEYDEF *keyinfo, uchar *page, uchar *key, 
                     uint key_length, my_off_t *new_page_offs)
{
  int n1, n2; /* Number of items in groups */

  SplitStruct *task;
  SplitStruct *cur;
  SplitStruct *stop;
  double *coord_buf;
  double *next_coord;
  double *old_coord;
  int n_dim;
  uchar *source_cur, *cur1, *cur2;
  uchar *new_page;
  int err_code = 0;

  uint nod_flag = mi_test_if_nod(page);
  uint full_length = key_length + (nod_flag ? nod_flag : 
                                   info->s->base.rec_reflength);

  int max_keys = (mi_getint(page)-2) / (full_length);

  n_dim = keyinfo->keysegs / 2;
  
  if (!(coord_buf= my_alloca(n_dim * 2 * sizeof(double) * (max_keys + 1 + 4) +
			     sizeof(SplitStruct) * (max_keys + 1))))
    return -1;

  task= (SplitStruct *)(coord_buf + n_dim * 2 * (max_keys + 1 + 4));

  next_coord = coord_buf;
 
  stop = task + max_keys;
  source_cur = rt_PAGE_FIRST_KEY(page, nod_flag);

  for (cur = task; cur < stop; ++cur, source_cur = rt_PAGE_NEXT_KEY(source_cur, 
       key_length, nod_flag))
  {
    cur->coords = reserve_coords(&next_coord, n_dim);
    cur->key = source_cur;
    rtree_d_mbr(keyinfo->seg, source_cur, key_length, cur->coords);
  }

  cur->coords = reserve_coords(&next_coord, n_dim);
  rtree_d_mbr(keyinfo->seg, key, key_length, cur->coords);
  cur->key = key;

  old_coord = next_coord;

  if (split_rtree_node(task, max_keys + 1,
       mi_getint(page) + full_length + 2, full_length, 
       rt_PAGE_MIN_SIZE(keyinfo->block_length),
       2, 2, &next_coord, n_dim))
  {
    err_code = 1;
    goto split_err;
  }

  if (!(new_page = (uchar*)my_alloca((uint)keyinfo->block_length)))
  {
    err_code= -1;
    goto split_err;
  }
  
  stop = task + (max_keys + 1);
  cur1 = rt_PAGE_FIRST_KEY(page, nod_flag);
  cur2 = rt_PAGE_FIRST_KEY(new_page, nod_flag);

  n1 = 0;
  n2 = 0;
  for (cur = task; cur < stop; ++cur)
  {
    uchar *to;
    if (cur->n_node == 1)
    {
      to = cur1;
      cur1 = rt_PAGE_NEXT_KEY(cur1, key_length, nod_flag);
      ++n1;
    }
    else
    {
      to = cur2;
      cur2 = rt_PAGE_NEXT_KEY(cur2, key_length, nod_flag);
      ++n2;
    }
    if (to != cur->key)
      memcpy(to - nod_flag, cur->key - nod_flag, full_length);
  }
 
  mi_putint(page, 2 + n1 * full_length, nod_flag);
  mi_putint(new_page, 2 + n2 * full_length, nod_flag);

  if ((*new_page_offs= _mi_new(info, keyinfo, DFLT_INIT_HITS)) == 
                                                               HA_OFFSET_ERROR)
    err_code= -1;
  else
    err_code= _mi_write_keypage(info, keyinfo, *new_page_offs,
                                DFLT_INIT_HITS, new_page);

  my_afree((byte*)new_page);

split_err:
  my_afree((byte*) coord_buf);
  return err_code;
}

#endif /*HAVE_RTREE_KEYS*/