summaryrefslogtreecommitdiff
path: root/mysys/lf_hash.c
blob: 5e407e9caece59acdb0459a9ac44d567ca8ad729 (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
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
/* Copyright (c) 2006, 2018, Oracle and/or its affiliates.
   Copyright (c) 2009, 2018, MariaDB

   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 */

/*
  extensible hash

  TODO
     try to get rid of dummy nodes ?
     for non-unique hash, count only _distinct_ values
     (but how to do it in lf_hash_delete ?)
*/
#include <my_global.h>
#include <m_string.h>
#include <my_sys.h>
#include <mysys_err.h>
#include <my_bit.h>
#include <lf.h>

/* An element of the list */
typedef struct {
  intptr volatile link; /* a pointer to the next element in a list and a flag */
  uint32 hashnr;        /* reversed hash number, for sorting                 */
  const uchar *key;
  size_t keylen;
  /*
    data is stored here, directly after the keylen.
    thus the pointer to data is (void*)(slist_element_ptr+1)
  */
} LF_SLIST;

const int LF_HASH_OVERHEAD= sizeof(LF_SLIST);

/*
  a structure to pass the context (pointers two the three successive elements
  in a list) from l_find to l_insert/l_delete
*/
typedef struct {
  intptr volatile *prev;
  LF_SLIST *curr, *next;
} CURSOR;

/*
  the last bit in LF_SLIST::link is a "deleted" flag.
  the helper macros below convert it to a pure pointer or a pure flag
*/
#define PTR(V)      (LF_SLIST *)((V) & (~(intptr)1))
#define DELETED(V)  ((V) & 1)

/** walk the list, searching for an element or invoking a callback

    Search for hashnr/key/keylen in the list starting from 'head' and
    position the cursor. The list is ORDER BY hashnr, key

    @param head         start walking the list from this node
    @param cs           charset for comparing keys, NULL if callback is used
    @param hashnr       hash number to search for
    @param key          key to search for OR data for the callback
    @param keylen       length of the key to compare, 0 if callback is used
    @param cursor       for returning the found element
    @param pins         see lf_alloc-pin.c
    @param callback     callback action, invoked for every element

  @note
    cursor is positioned in either case
    pins[0..2] are used, they are NOT removed on return
    callback might see some elements twice (because of retries)

  @return
    if find: 0 - not found
             1 - found
    if callback:
             0 - ok
             1 - error (callbck returned 1)
*/
static int l_find(LF_SLIST * volatile *head, CHARSET_INFO *cs, uint32 hashnr,
                 const uchar *key, uint keylen, CURSOR *cursor, LF_PINS *pins,
                 my_hash_walk_action callback)
{
  uint32       cur_hashnr;
  const uchar  *cur_key;
  uint         cur_keylen;
  intptr       link;

  DBUG_ASSERT(!cs || !callback);        /* should not be set both */
  DBUG_ASSERT(!keylen || !callback);    /* should not be set both */

retry:
  cursor->prev= (intptr *)head;
  do { /* PTR() isn't necessary below, head is a dummy node */
    cursor->curr= (LF_SLIST *)(*cursor->prev);
    lf_pin(pins, 1, cursor->curr);
  } while (my_atomic_loadptr((void**)cursor->prev) != cursor->curr &&
                              LF_BACKOFF);
  for (;;)
  {
    if (unlikely(!cursor->curr))
      return 0; /* end of the list */

    cur_hashnr= cursor->curr->hashnr;
    cur_keylen= cursor->curr->keylen;
    cur_key= cursor->curr->key;

    do {
      link= cursor->curr->link;
      cursor->next= PTR(link);
      lf_pin(pins, 0, cursor->next);
    } while (link != cursor->curr->link && LF_BACKOFF);

    if (!DELETED(link))
    {
      if (unlikely(callback))
      {
        if (cur_hashnr & 1 && callback(cursor->curr + 1, (void*)key))
          return 1;
      }
      else if (cur_hashnr >= hashnr)
      {
        int r= 1;
        if (cur_hashnr > hashnr ||
            (r= my_strnncoll(cs, cur_key, cur_keylen, key, keylen)) >= 0)
          return !r;
      }
      cursor->prev= &(cursor->curr->link);
      if (!(cur_hashnr & 1)) /* dummy node */
        head= (LF_SLIST **)cursor->prev;
      lf_pin(pins, 2, cursor->curr);
    }
    else
    {
      /*
        we found a deleted node - be nice, help the other thread
        and remove this deleted node
      */
      if (my_atomic_casptr((void **) cursor->prev,
                           (void **) &cursor->curr, cursor->next) && LF_BACKOFF)
        lf_alloc_free(pins, cursor->curr);
      else
        goto retry;
    }
    cursor->curr= cursor->next;
    lf_pin(pins, 1, cursor->curr);
  }
}

/*
  DESCRIPTION
    insert a 'node' in the list that starts from 'head' in the correct
    position (as found by l_find)

  RETURN
    0     - inserted
    not 0 - a pointer to a duplicate (not pinned and thus unusable)

  NOTE
    it uses pins[0..2], on return all pins are removed.
    if there're nodes with the same key value, a new node is added before them.
*/
static LF_SLIST *l_insert(LF_SLIST * volatile *head, CHARSET_INFO *cs,
                         LF_SLIST *node, LF_PINS *pins, uint flags)
{
  CURSOR         cursor;
  int            res;

  for (;;)
  {
    if (l_find(head, cs, node->hashnr, node->key, node->keylen,
              &cursor, pins, 0) &&
        (flags & LF_HASH_UNIQUE))
    {
      res= 0; /* duplicate found */
      break;
    }
    else
    {
      node->link= (intptr)cursor.curr;
      DBUG_ASSERT(node->link != (intptr)node); /* no circular references */
      DBUG_ASSERT(cursor.prev != &node->link); /* no circular references */
      if (my_atomic_casptr((void **) cursor.prev,
                           (void **)(char*) &cursor.curr, node))
      {
        res= 1; /* inserted ok */
        break;
      }
    }
  }
  lf_unpin(pins, 0);
  lf_unpin(pins, 1);
  lf_unpin(pins, 2);
  /*
    Note that cursor.curr is not pinned here and the pointer is unreliable,
    the object may disappear anytime. But if it points to a dummy node, the
    pointer is safe, because dummy nodes are never freed - initialize_bucket()
    uses this fact.
  */
  return res ? 0 : cursor.curr;
}

/*
  DESCRIPTION
    deletes a node as identified by hashnr/keey/keylen from the list
    that starts from 'head'

  RETURN
    0 - ok
    1 - not found

  NOTE
    it uses pins[0..2], on return all pins are removed.
*/
static int l_delete(LF_SLIST * volatile *head, CHARSET_INFO *cs, uint32 hashnr,
                   const uchar *key, uint keylen, LF_PINS *pins)
{
  CURSOR cursor;
  int res;

  for (;;)
  {
    if (!l_find(head, cs, hashnr, key, keylen, &cursor, pins, 0))
    {
      res= 1; /* not found */
      break;
    }
    else
    {
      /* mark the node deleted */
      if (my_atomic_casptr((void **) (char*) &(cursor.curr->link),
                           (void **) (char*) &cursor.next,
                           (void *)(((intptr)cursor.next) | 1)))
      {
        /* and remove it from the list */
        if (my_atomic_casptr((void **)cursor.prev,
                             (void **)(char*)&cursor.curr, cursor.next))
          lf_alloc_free(pins, cursor.curr);
        else
        {
          /*
            somebody already "helped" us and removed the node ?
            Let's check if we need to help that someone too!
            (to ensure the number of "set DELETED flag" actions
            is equal to the number of "remove from the list" actions)
          */
          l_find(head, cs, hashnr, key, keylen, &cursor, pins, 0);
        }
        res= 0;
        break;
      }
    }
  }
  lf_unpin(pins, 0);
  lf_unpin(pins, 1);
  lf_unpin(pins, 2);
  return res;
}

/*
  DESCRIPTION
    searches for a node as identified by hashnr/keey/keylen in the list
    that starts from 'head'

  RETURN
    0 - not found
    node - found

  NOTE
    it uses pins[0..2], on return the pin[2] keeps the node found
    all other pins are removed.
*/
static LF_SLIST *l_search(LF_SLIST * volatile *head, CHARSET_INFO *cs,
                         uint32 hashnr, const uchar *key, uint keylen,
                         LF_PINS *pins)
{
  CURSOR cursor;
  int res= l_find(head, cs, hashnr, key, keylen, &cursor, pins, 0);
  if (res)
    lf_pin(pins, 2, cursor.curr);
  else
    lf_unpin(pins, 2);
  lf_unpin(pins, 1);
  lf_unpin(pins, 0);
  return res ? cursor.curr : 0;
}

static inline const uchar* hash_key(const LF_HASH *hash,
                                    const uchar *record, size_t *length)
{
  if (hash->get_key)
    return (*hash->get_key)(record, length, 0);
  *length= hash->key_length;
  return record + hash->key_offset;
}

/*
  Compute the hash key value from the raw key.

  @note, that the hash value is limited to 2^31, because we need one
  bit to distinguish between normal and dummy nodes.
*/
static inline my_hash_value_type calc_hash(const CHARSET_INFO *cs,
                                           const uchar *key,
                                           size_t keylen)
{
  ulong nr1= 1, nr2= 4;
  cs->coll->hash_sort(cs, (uchar*) key, keylen, &nr1, &nr2);
  return nr1;
}

#define MAX_LOAD 1.0    /* average number of elements in a bucket */

static int initialize_bucket(LF_HASH *, LF_SLIST * volatile*, uint, LF_PINS *);

static void default_initializer(LF_HASH *hash, void *dst, const void *src)
{
  memcpy(dst, src, hash->element_size);
}

/*
  Initializes lf_hash, the arguments are compatible with hash_init

  @note element_size sets both the size of allocated memory block for
  lf_alloc and a size of memcpy'ed block size in lf_hash_insert. Typically
  they are the same, indeed. But LF_HASH::element_size can be decreased
  after lf_hash_init, and then lf_alloc will allocate larger block that
  lf_hash_insert will copy over. It is desirable if part of the element
  is expensive to initialize - for example if there is a mutex or
  DYNAMIC_ARRAY. In this case they should be initialize in the
  LF_ALLOCATOR::constructor, and lf_hash_insert should not overwrite them.

  The above works well with PODS. For more complex cases (e.g. C++ classes
  with private members) use initializer function.
*/
void lf_hash_init(LF_HASH *hash, uint element_size, uint flags,
                  uint key_offset, uint key_length, my_hash_get_key get_key,
                  CHARSET_INFO *charset)
{
  lf_alloc_init(&hash->alloc, sizeof(LF_SLIST)+element_size,
                offsetof(LF_SLIST, key));
  lf_dynarray_init(&hash->array, sizeof(LF_SLIST *));
  hash->size= 1;
  hash->count= 0;
  hash->element_size= element_size;
  hash->flags= flags;
  hash->charset= charset ? charset : &my_charset_bin;
  hash->key_offset= key_offset;
  hash->key_length= key_length;
  hash->get_key= get_key;
  hash->initializer= default_initializer;
  hash->hash_function= calc_hash;
  DBUG_ASSERT(get_key ? !key_offset && !key_length : key_length);
}

void lf_hash_destroy(LF_HASH *hash)
{
  LF_SLIST *el, **head= (LF_SLIST **)lf_dynarray_value(&hash->array, 0);

  if (head)
  {
    el= *head;
    while (el)
    {
      intptr next= el->link;
      if (el->hashnr & 1)
        lf_alloc_direct_free(&hash->alloc, el); /* normal node */
      else
        my_free(el); /* dummy node */
      el= (LF_SLIST *)next;
    }
  }
  lf_alloc_destroy(&hash->alloc);
  lf_dynarray_destroy(&hash->array);
}

/*
  DESCRIPTION
    inserts a new element to a hash. it will have a _copy_ of
    data, not a pointer to it.

  RETURN
    0 - inserted
    1 - didn't (unique key conflict)
   -1 - out of memory

  NOTE
    see l_insert() for pin usage notes
*/
int lf_hash_insert(LF_HASH *hash, LF_PINS *pins, const void *data)
{
  int csize, bucket, hashnr;
  LF_SLIST *node, * volatile *el;

  node= (LF_SLIST *)lf_alloc_new(pins);
  if (unlikely(!node))
    return -1;
  hash->initializer(hash, node + 1, data);
  node->key= hash_key(hash, (uchar *)(node+1), &node->keylen);
  hashnr= hash->hash_function(hash->charset, node->key, node->keylen) & INT_MAX32;
  bucket= hashnr % hash->size;
  el= lf_dynarray_lvalue(&hash->array, bucket);
  if (unlikely(!el))
    return -1;
  if (*el == NULL && unlikely(initialize_bucket(hash, el, bucket, pins)))
    return -1;
  node->hashnr= my_reverse_bits(hashnr) | 1; /* normal node */
  if (l_insert(el, hash->charset, node, pins, hash->flags))
  {
    lf_alloc_free(pins, node);
    return 1;
  }
  csize= hash->size;
  if ((my_atomic_add32(&hash->count, 1)+1.0) / csize > MAX_LOAD)
    my_atomic_cas32(&hash->size, &csize, csize*2);
  return 0;
}

/*
  DESCRIPTION
    deletes an element with the given key from the hash (if a hash is
    not unique and there're many elements with this key - the "first"
    matching element is deleted)
  RETURN
    0 - deleted
    1 - didn't (not found)
  NOTE
    see l_delete() for pin usage notes
*/
int lf_hash_delete(LF_HASH *hash, LF_PINS *pins, const void *key, uint keylen)
{
  LF_SLIST * volatile *el;
  uint bucket, hashnr;

  hashnr= hash->hash_function(hash->charset, (uchar *)key, keylen) & INT_MAX32;

  /* hide OOM errors - if we cannot initialize a bucket, try the previous one */
  for (bucket= hashnr % hash->size; ;bucket= my_clear_highest_bit(bucket))
  {
    el= lf_dynarray_lvalue(&hash->array, bucket);
    if (el && (*el || initialize_bucket(hash, el, bucket, pins) == 0))
      break;
    if (unlikely(bucket == 0))
      return 1; /* if there's no bucket==0, the hash is empty */
  }
  if (l_delete(el, hash->charset, my_reverse_bits(hashnr) | 1,
              (uchar *)key, keylen, pins))
  {
    return 1;
  }
  my_atomic_add32(&hash->count, -1);
  return 0;
}

/*
  RETURN
    a pointer to an element with the given key (if a hash is not unique and
    there're many elements with this key - the "first" matching element)
    NULL         if nothing is found

  NOTE
    see l_search() for pin usage notes
*/
void *lf_hash_search_using_hash_value(LF_HASH *hash, LF_PINS *pins,
                                      my_hash_value_type hashnr,
                                      const void *key, uint keylen)
{
  LF_SLIST * volatile *el, *found;
  uint bucket;

  /* hide OOM errors - if we cannot initialize a bucket, try the previous one */
  for (bucket= hashnr % hash->size; ;bucket= my_clear_highest_bit(bucket))
  {
    el= lf_dynarray_lvalue(&hash->array, bucket);
    if (el && (*el || initialize_bucket(hash, el, bucket, pins) == 0))
      break;
    if (unlikely(bucket == 0))
      return 0; /* if there's no bucket==0, the hash is empty */
  }
  found= l_search(el, hash->charset, my_reverse_bits(hashnr) | 1,
                 (uchar *)key, keylen, pins);
  return found ? found+1 : 0;
}


/**
   Iterate over all elements in hash and call function with the element

   @note
   If one of 'action' invocations returns 1 the iteration aborts.
   'action' might see some elements twice!

   @retval 0    ok
   @retval 1    error (action returned 1)
*/
int lf_hash_iterate(LF_HASH *hash, LF_PINS *pins,
                    my_hash_walk_action action, void *argument)
{
  CURSOR cursor;
  uint bucket= 0;
  int res;
  LF_SLIST * volatile *el;

  el= lf_dynarray_lvalue(&hash->array, bucket);
  if (unlikely(!el))
    return 0; /* if there's no bucket==0, the hash is empty */
  if (*el == NULL && unlikely(initialize_bucket(hash, el, bucket, pins)))
    return 0; /* if there's no bucket==0, the hash is empty */

  res= l_find(el, 0, 0, (uchar*)argument, 0, &cursor, pins, action);

  lf_unpin(pins, 2);
  lf_unpin(pins, 1);
  lf_unpin(pins, 0);
  return res;
}

void *lf_hash_search(LF_HASH *hash, LF_PINS *pins, const void *key, uint keylen)
{
  return lf_hash_search_using_hash_value(hash, pins,
                                         hash->hash_function(hash->charset,
                                                             (uchar*) key,
                                                             keylen) & INT_MAX32,
                                         key, keylen);
}

static const uchar *dummy_key= (uchar*)"";

/*
  RETURN
    0 - ok
   -1 - out of memory
*/
static int initialize_bucket(LF_HASH *hash, LF_SLIST * volatile *node,
                              uint bucket, LF_PINS *pins)
{
  uint parent= my_clear_highest_bit(bucket);
  LF_SLIST *dummy= (LF_SLIST *)my_malloc(sizeof(LF_SLIST), MYF(MY_WME));
  LF_SLIST **tmp= 0, *cur;
  LF_SLIST * volatile *el= lf_dynarray_lvalue(&hash->array, parent);
  if (unlikely(!el || !dummy))
    return -1;
  if (*el == NULL && bucket &&
      unlikely(initialize_bucket(hash, el, parent, pins)))
  {
    my_free(dummy);
    return -1;
  }
  dummy->hashnr= my_reverse_bits(bucket) | 0; /* dummy node */
  dummy->key= dummy_key;
  dummy->keylen= 0;
  if ((cur= l_insert(el, hash->charset, dummy, pins, LF_HASH_UNIQUE)))
  {
    my_free(dummy);
    dummy= cur;
  }
  my_atomic_casptr((void **)node, (void **)(char*) &tmp, dummy);
  /*
    note that if the CAS above failed (after l_insert() succeeded),
    it would mean that some other thread has executed l_insert() for
    the same dummy node, its l_insert() failed, it picked up our
    dummy node (in "dummy= cur") and executed the same CAS as above.
    Which means that even if CAS above failed we don't need to retry,
    and we should not free(dummy) - there's no memory leak here
  */
  return 0;
}