summaryrefslogtreecommitdiff
path: root/src/db.c
blob: 6447838caa7e19f98378eeeed940c64de222001d (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
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
#include "redis.h"

#include <signal.h>
#include <ctype.h>

void SlotToKeyAdd(robj *key);
void SlotToKeyDel(robj *key);

/*-----------------------------------------------------------------------------
 * C-level DB API
 *----------------------------------------------------------------------------*/

robj *lookupKey(redisDb *db, robj *key) {
    dictEntry *de = dictFind(db->dict,key->ptr);
    if (de) {
        robj *val = dictGetVal(de);

        /* Update the access time for the aging algorithm.
         * Don't do it if we have a saving child, as this will trigger
         * a copy on write madness. */
        if (server.rdb_child_pid == -1 && server.aof_child_pid == -1)
            val->lru = server.lruclock;
        return val;
    } else {
        return NULL;
    }
}

robj *lookupKeyRead(redisDb *db, robj *key) {
    robj *val;

    expireIfNeeded(db,key);
    val = lookupKey(db,key);
    if (val == NULL)
        server.stat_keyspace_misses++;
    else
        server.stat_keyspace_hits++;
    return val;
}

robj *lookupKeyWrite(redisDb *db, robj *key) {
    expireIfNeeded(db,key);
    return lookupKey(db,key);
}

robj *lookupKeyReadOrReply(redisClient *c, robj *key, robj *reply) {
    robj *o = lookupKeyRead(c->db, key);
    if (!o) addReply(c,reply);
    return o;
}

robj *lookupKeyWriteOrReply(redisClient *c, robj *key, robj *reply) {
    robj *o = lookupKeyWrite(c->db, key);
    if (!o) addReply(c,reply);
    return o;
}

/* Add the key to the DB. It's up to the caller to increment the reference
 * counte of the value if needed.
 *
 * The program is aborted if the key already exists. */
void dbAdd(redisDb *db, robj *key, robj *val) {
    sds copy = sdsdup(key->ptr);
    int retval = dictAdd(db->dict, copy, val);

    redisAssertWithInfo(NULL,key,retval == REDIS_OK);
    if (server.cluster_enabled) SlotToKeyAdd(key);
 }

/* Overwrite an existing key with a new value. Incrementing the reference
 * count of the new value is up to the caller.
 * This function does not modify the expire time of the existing key.
 *
 * The program is aborted if the key was not already present. */
void dbOverwrite(redisDb *db, robj *key, robj *val) {
    struct dictEntry *de = dictFind(db->dict,key->ptr);
    
    redisAssertWithInfo(NULL,key,de != NULL);
    dictReplace(db->dict, key->ptr, val);
}

/* High level Set operation. This function can be used in order to set
 * a key, whatever it was existing or not, to a new object.
 *
 * 1) The ref count of the value object is incremented.
 * 2) clients WATCHing for the destination key notified.
 * 3) The expire time of the key is reset (the key is made persistent). */
void setKey(redisDb *db, robj *key, robj *val) {
    if (lookupKeyWrite(db,key) == NULL) {
        dbAdd(db,key,val);
    } else {
        dbOverwrite(db,key,val);
    }
    incrRefCount(val);
    removeExpire(db,key);
    signalModifiedKey(db,key);
}

int dbExists(redisDb *db, robj *key) {
    return dictFind(db->dict,key->ptr) != NULL;
}

/* Return a random key, in form of a Redis object.
 * If there are no keys, NULL is returned.
 *
 * The function makes sure to return keys not already expired. */
robj *dbRandomKey(redisDb *db) {
    struct dictEntry *de;

    while(1) {
        sds key;
        robj *keyobj;

        de = dictGetRandomKey(db->dict);
        if (de == NULL) return NULL;

        key = dictGetKey(de);
        keyobj = createStringObject(key,sdslen(key));
        if (dictFind(db->expires,key)) {
            if (expireIfNeeded(db,keyobj)) {
                decrRefCount(keyobj);
                continue; /* search for another key. This expired. */
            }
        }
        return keyobj;
    }
}

/* Delete a key, value, and associated expiration entry if any, from the DB */
int dbDelete(redisDb *db, robj *key) {
    /* Deleting an entry from the expires dict will not free the sds of
     * the key, because it is shared with the main dictionary. */
    if (dictSize(db->expires) > 0) dictDelete(db->expires,key->ptr);
    if (dictDelete(db->dict,key->ptr) == DICT_OK) {
        if (server.cluster_enabled) SlotToKeyDel(key);
        return 1;
    } else {
        return 0;
    }
}

long long emptyDb() {
    int j;
    long long removed = 0;

    for (j = 0; j < server.dbnum; j++) {
        removed += dictSize(server.db[j].dict);
        dictEmpty(server.db[j].dict);
        dictEmpty(server.db[j].expires);
    }
    return removed;
}

int selectDb(redisClient *c, int id) {
    if (id < 0 || id >= server.dbnum)
        return REDIS_ERR;
    c->db = &server.db[id];
    return REDIS_OK;
}

/*-----------------------------------------------------------------------------
 * Hooks for key space changes.
 *
 * Every time a key in the database is modified the function
 * signalModifiedKey() is called.
 *
 * Every time a DB is flushed the function signalFlushDb() is called.
 *----------------------------------------------------------------------------*/

void signalModifiedKey(redisDb *db, robj *key) {
    touchWatchedKey(db,key);
}

void signalFlushedDb(int dbid) {
    touchWatchedKeysOnFlush(dbid);
}

/*-----------------------------------------------------------------------------
 * Type agnostic commands operating on the key space
 *----------------------------------------------------------------------------*/

void flushdbCommand(redisClient *c) {
    server.dirty += dictSize(c->db->dict);
    signalFlushedDb(c->db->id);
    dictEmpty(c->db->dict);
    dictEmpty(c->db->expires);
    addReply(c,shared.ok);
}

void flushallCommand(redisClient *c) {
    signalFlushedDb(-1);
    server.dirty += emptyDb();
    addReply(c,shared.ok);
    if (server.rdb_child_pid != -1) {
        kill(server.rdb_child_pid,SIGKILL);
        rdbRemoveTempFile(server.rdb_child_pid);
    }
    if (server.saveparamslen > 0) {
        /* Normally rdbSave() will reset dirty, but we don't want this here
         * as otherwise FLUSHALL will not be replicated nor put into the AOF. */
        int saved_dirty = server.dirty;
        rdbSave(server.rdb_filename);
        server.dirty = saved_dirty;
    }
    server.dirty++;
}

void delCommand(redisClient *c) {
    int deleted = 0, j;

    for (j = 1; j < c->argc; j++) {
        if (dbDelete(c->db,c->argv[j])) {
            signalModifiedKey(c->db,c->argv[j]);
            server.dirty++;
            deleted++;
        }
    }
    addReplyLongLong(c,deleted);
}

void existsCommand(redisClient *c) {
    expireIfNeeded(c->db,c->argv[1]);
    if (dbExists(c->db,c->argv[1])) {
        addReply(c, shared.cone);
    } else {
        addReply(c, shared.czero);
    }
}

void selectCommand(redisClient *c) {
    int id = atoi(c->argv[1]->ptr);

    if (server.cluster_enabled && id != 0) {
        addReplyError(c,"SELECT is not allowed in cluster mode");
        return;
    }
    if (selectDb(c,id) == REDIS_ERR) {
        addReplyError(c,"invalid DB index");
    } else {
        addReply(c,shared.ok);
    }
}

void randomkeyCommand(redisClient *c) {
    robj *key;

    if ((key = dbRandomKey(c->db)) == NULL) {
        addReply(c,shared.nullbulk);
        return;
    }

    addReplyBulk(c,key);
    decrRefCount(key);
}

void keysCommand(redisClient *c) {
    dictIterator *di;
    dictEntry *de;
    sds pattern = c->argv[1]->ptr;
    int plen = sdslen(pattern), allkeys;
    unsigned long numkeys = 0;
    void *replylen = addDeferredMultiBulkLength(c);

    di = dictGetSafeIterator(c->db->dict);
    allkeys = (pattern[0] == '*' && pattern[1] == '\0');
    while((de = dictNext(di)) != NULL) {
        sds key = dictGetKey(de);
        robj *keyobj;

        if (allkeys || stringmatchlen(pattern,plen,key,sdslen(key),0)) {
            keyobj = createStringObject(key,sdslen(key));
            if (expireIfNeeded(c->db,keyobj) == 0) {
                addReplyBulk(c,keyobj);
                numkeys++;
            }
            decrRefCount(keyobj);
        }
    }
    dictReleaseIterator(di);
    setDeferredMultiBulkLength(c,replylen,numkeys);
}

void dbsizeCommand(redisClient *c) {
    addReplyLongLong(c,dictSize(c->db->dict));
}

void lastsaveCommand(redisClient *c) {
    addReplyLongLong(c,server.lastsave);
}

void typeCommand(redisClient *c) {
    robj *o;
    char *type;

    o = lookupKeyRead(c->db,c->argv[1]);
    if (o == NULL) {
        type = "none";
    } else {
        switch(o->type) {
        case REDIS_STRING: type = "string"; break;
        case REDIS_LIST: type = "list"; break;
        case REDIS_SET: type = "set"; break;
        case REDIS_ZSET: type = "zset"; break;
        case REDIS_HASH: type = "hash"; break;
        default: type = "unknown"; break;
        }
    }
    addReplyStatus(c,type);
}

void shutdownCommand(redisClient *c) {
    int flags = 0;

    if (c->argc > 2) {
        addReply(c,shared.syntaxerr);
        return;
    } else if (c->argc == 2) {
        if (!strcasecmp(c->argv[1]->ptr,"nosave")) {
            flags |= REDIS_SHUTDOWN_NOSAVE;
        } else if (!strcasecmp(c->argv[1]->ptr,"save")) {
            flags |= REDIS_SHUTDOWN_SAVE;
        } else {
            addReply(c,shared.syntaxerr);
            return;
        }
    }
    if (prepareForShutdown(flags) == REDIS_OK) exit(0);
    addReplyError(c,"Errors trying to SHUTDOWN. Check logs.");
}

void renameGenericCommand(redisClient *c, int nx) {
    robj *o;
    long long expire;

    /* To use the same key as src and dst is probably an error */
    if (sdscmp(c->argv[1]->ptr,c->argv[2]->ptr) == 0) {
        addReply(c,shared.sameobjecterr);
        return;
    }

    if ((o = lookupKeyWriteOrReply(c,c->argv[1],shared.nokeyerr)) == NULL)
        return;

    incrRefCount(o);
    expire = getExpire(c->db,c->argv[1]);
    if (lookupKeyWrite(c->db,c->argv[2]) != NULL) {
        if (nx) {
            decrRefCount(o);
            addReply(c,shared.czero);
            return;
        }
        /* Overwrite: delete the old key before creating the new one with the same name. */
        dbDelete(c->db,c->argv[2]);
    }
    dbAdd(c->db,c->argv[2],o);
    if (expire != -1) setExpire(c->db,c->argv[2],expire);
    dbDelete(c->db,c->argv[1]);
    signalModifiedKey(c->db,c->argv[1]);
    signalModifiedKey(c->db,c->argv[2]);
    server.dirty++;
    addReply(c,nx ? shared.cone : shared.ok);
}

void renameCommand(redisClient *c) {
    renameGenericCommand(c,0);
}

void renamenxCommand(redisClient *c) {
    renameGenericCommand(c,1);
}

void moveCommand(redisClient *c) {
    robj *o;
    redisDb *src, *dst;
    int srcid;

    if (server.cluster_enabled) {
        addReplyError(c,"MOVE is not allowed in cluster mode");
        return;
    }

    /* Obtain source and target DB pointers */
    src = c->db;
    srcid = c->db->id;
    if (selectDb(c,atoi(c->argv[2]->ptr)) == REDIS_ERR) {
        addReply(c,shared.outofrangeerr);
        return;
    }
    dst = c->db;
    selectDb(c,srcid); /* Back to the source DB */

    /* If the user is moving using as target the same
     * DB as the source DB it is probably an error. */
    if (src == dst) {
        addReply(c,shared.sameobjecterr);
        return;
    }

    /* Check if the element exists and get a reference */
    o = lookupKeyWrite(c->db,c->argv[1]);
    if (!o) {
        addReply(c,shared.czero);
        return;
    }

    /* Return zero if the key already exists in the target DB */
    if (lookupKeyWrite(dst,c->argv[1]) != NULL) {
        addReply(c,shared.czero);
        return;
    }
    dbAdd(dst,c->argv[1],o);
    incrRefCount(o);

    /* OK! key moved, free the entry in the source DB */
    dbDelete(src,c->argv[1]);
    server.dirty++;
    addReply(c,shared.cone);
}

/*-----------------------------------------------------------------------------
 * Expires API
 *----------------------------------------------------------------------------*/

int removeExpire(redisDb *db, robj *key) {
    /* An expire may only be removed if there is a corresponding entry in the
     * main dict. Otherwise, the key will never be freed. */
    redisAssertWithInfo(NULL,key,dictFind(db->dict,key->ptr) != NULL);
    return dictDelete(db->expires,key->ptr) == DICT_OK;
}

void setExpire(redisDb *db, robj *key, long long when) {
    dictEntry *kde, *de;

    /* Reuse the sds from the main dict in the expire dict */
    kde = dictFind(db->dict,key->ptr);
    redisAssertWithInfo(NULL,key,kde != NULL);
    de = dictReplaceRaw(db->expires,dictGetKey(kde));
    dictSetSignedIntegerVal(de,when);
}

/* Return the expire time of the specified key, or -1 if no expire
 * is associated with this key (i.e. the key is non volatile) */
long long getExpire(redisDb *db, robj *key) {
    dictEntry *de;

    /* No expire? return ASAP */
    if (dictSize(db->expires) == 0 ||
       (de = dictFind(db->expires,key->ptr)) == NULL) return -1;

    /* The entry was found in the expire dict, this means it should also
     * be present in the main dict (safety check). */
    redisAssertWithInfo(NULL,key,dictFind(db->dict,key->ptr) != NULL);
    return dictGetSignedIntegerVal(de);
}

/* Propagate expires into slaves and the AOF file.
 * When a key expires in the master, a DEL operation for this key is sent
 * to all the slaves and the AOF file if enabled.
 *
 * This way the key expiry is centralized in one place, and since both
 * AOF and the master->slave link guarantee operation ordering, everything
 * will be consistent even if we allow write operations against expiring
 * keys. */
void propagateExpire(redisDb *db, robj *key) {
    robj *argv[2];

    argv[0] = shared.del;
    argv[1] = key;
    incrRefCount(argv[0]);
    incrRefCount(argv[1]);

    if (server.aof_state != REDIS_AOF_OFF)
        feedAppendOnlyFile(server.delCommand,db->id,argv,2);
    if (listLength(server.slaves))
        replicationFeedSlaves(server.slaves,db->id,argv,2);

    decrRefCount(argv[0]);
    decrRefCount(argv[1]);
}

int expireIfNeeded(redisDb *db, robj *key) {
    long long when = getExpire(db,key);

    if (when < 0) return 0; /* No expire for this key */

    /* Don't expire anything while loading. It will be done later. */
    if (server.loading) return 0;

    /* If we are running in the context of a slave, return ASAP:
     * the slave key expiration is controlled by the master that will
     * send us synthesized DEL operations for expired keys.
     *
     * Still we try to return the right information to the caller, 
     * that is, 0 if we think the key should be still valid, 1 if
     * we think the key is expired at this time. */
    if (server.masterhost != NULL) {
        return mstime() > when;
    }

    /* Return when this key has not expired */
    if (mstime() <= when) return 0;

    /* Delete the key */
    server.stat_expiredkeys++;
    propagateExpire(db,key);
    return dbDelete(db,key);
}

/*-----------------------------------------------------------------------------
 * Expires Commands
 *----------------------------------------------------------------------------*/

/* This is the generic command implementation for EXPIRE, PEXPIRE, EXPIREAT
 * and PEXPIREAT. Because the commad second argument may be relative or absolute
 * the "basetime" argument is used to signal what the base time is (either 0
 * for *AT variants of the command, or the current time for relative expires).
 *
 * unit is either UNIT_SECONDS or UNIT_MILLISECONDS, and is only used for
 * the argv[2] parameter. The basetime is always specified in milliesconds. */
void expireGenericCommand(redisClient *c, long long basetime, int unit) {
    dictEntry *de;
    robj *key = c->argv[1], *param = c->argv[2];
    long long when; /* unix time in milliseconds when the key will expire. */

    if (getLongLongFromObjectOrReply(c, param, &when, NULL) != REDIS_OK)
        return;

    if (unit == UNIT_SECONDS) when *= 1000;
    when += basetime;

    de = dictFind(c->db->dict,key->ptr);
    if (de == NULL) {
        addReply(c,shared.czero);
        return;
    }
    /* EXPIRE with negative TTL, or EXPIREAT with a timestamp into the past
     * should never be executed as a DEL when load the AOF or in the context
     * of a slave instance.
     *
     * Instead we take the other branch of the IF statement setting an expire
     * (possibly in the past) and wait for an explicit DEL from the master. */
    if (when <= mstime() && !server.loading && !server.masterhost) {
        robj *aux;

        redisAssertWithInfo(c,key,dbDelete(c->db,key));
        server.dirty++;

        /* Replicate/AOF this as an explicit DEL. */
        aux = createStringObject("DEL",3);
        rewriteClientCommandVector(c,2,aux,key);
        decrRefCount(aux);
        signalModifiedKey(c->db,key);
        addReply(c, shared.cone);
        return;
    } else {
        setExpire(c->db,key,when);
        addReply(c,shared.cone);
        signalModifiedKey(c->db,key);
        server.dirty++;
        return;
    }
}

void expireCommand(redisClient *c) {
    expireGenericCommand(c,mstime(),UNIT_SECONDS);
}

void expireatCommand(redisClient *c) {
    expireGenericCommand(c,0,UNIT_SECONDS);
}

void pexpireCommand(redisClient *c) {
    expireGenericCommand(c,mstime(),UNIT_MILLISECONDS);
}

void pexpireatCommand(redisClient *c) {
    expireGenericCommand(c,0,UNIT_MILLISECONDS);
}

void ttlGenericCommand(redisClient *c, int output_ms) {
    long long expire, ttl = -1;

    expire = getExpire(c->db,c->argv[1]);
    if (expire != -1) {
        ttl = expire-mstime();
        if (ttl < 0) ttl = -1;
    }
    if (ttl == -1) {
        addReplyLongLong(c,-1);
    } else {
        addReplyLongLong(c,output_ms ? ttl : ((ttl+500)/1000));
    }
}

void ttlCommand(redisClient *c) {
    ttlGenericCommand(c, 0);
}

void pttlCommand(redisClient *c) {
    ttlGenericCommand(c, 1);
}

void persistCommand(redisClient *c) {
    dictEntry *de;

    de = dictFind(c->db->dict,c->argv[1]->ptr);
    if (de == NULL) {
        addReply(c,shared.czero);
    } else {
        if (removeExpire(c->db,c->argv[1])) {
            addReply(c,shared.cone);
            server.dirty++;
        } else {
            addReply(c,shared.czero);
        }
    }
}

/* -----------------------------------------------------------------------------
 * API to get key arguments from commands
 * ---------------------------------------------------------------------------*/

int *getKeysUsingCommandTable(struct redisCommand *cmd,robj **argv, int argc, int *numkeys) {
    int j, i = 0, last, *keys;
    REDIS_NOTUSED(argv);

    if (cmd->firstkey == 0) {
        *numkeys = 0;
        return NULL;
    }
    last = cmd->lastkey;
    if (last < 0) last = argc+last;
    keys = zmalloc(sizeof(int)*((last - cmd->firstkey)+1));
    for (j = cmd->firstkey; j <= last; j += cmd->keystep) {
        redisAssert(j < argc);
        keys[i++] = j;
    }
    *numkeys = i;
    return keys;
}

int *getKeysFromCommand(struct redisCommand *cmd,robj **argv, int argc, int *numkeys, int flags) {
    if (cmd->getkeys_proc) {
        return cmd->getkeys_proc(cmd,argv,argc,numkeys,flags);
    } else {
        return getKeysUsingCommandTable(cmd,argv,argc,numkeys);
    }
}

void getKeysFreeResult(int *result) {
    zfree(result);
}

int *noPreloadGetKeys(struct redisCommand *cmd,robj **argv, int argc, int *numkeys, int flags) {
    if (flags & REDIS_GETKEYS_PRELOAD) {
        *numkeys = 0;
        return NULL;
    } else {
        return getKeysUsingCommandTable(cmd,argv,argc,numkeys);
    }
}

int *renameGetKeys(struct redisCommand *cmd,robj **argv, int argc, int *numkeys, int flags) {
    if (flags & REDIS_GETKEYS_PRELOAD) {
        int *keys = zmalloc(sizeof(int));
        *numkeys = 1;
        keys[0] = 1;
        return keys;
    } else {
        return getKeysUsingCommandTable(cmd,argv,argc,numkeys);
    }
}

int *zunionInterGetKeys(struct redisCommand *cmd,robj **argv, int argc, int *numkeys, int flags) {
    int i, num, *keys;
    REDIS_NOTUSED(cmd);
    REDIS_NOTUSED(flags);

    num = atoi(argv[2]->ptr);
    /* Sanity check. Don't return any key if the command is going to
     * reply with syntax error. */
    if (num > (argc-3)) {
        *numkeys = 0;
        return NULL;
    }
    keys = zmalloc(sizeof(int)*num);
    for (i = 0; i < num; i++) keys[i] = 3+i;
    *numkeys = num;
    return keys;
}

/* Slot to Key API. This is used by Redis Cluster in order to obtain in
 * a fast way a key that belongs to a specified hash slot. This is useful
 * while rehashing the cluster. */
void SlotToKeyAdd(robj *key) {
    unsigned int hashslot = keyHashSlot(key->ptr,sdslen(key->ptr));

    zslInsert(server.cluster.slots_to_keys,hashslot,key);
    incrRefCount(key);
}

void SlotToKeyDel(robj *key) {
    unsigned int hashslot = keyHashSlot(key->ptr,sdslen(key->ptr));

    zslDelete(server.cluster.slots_to_keys,hashslot,key);
}

unsigned int GetKeysInSlot(unsigned int hashslot, robj **keys, unsigned int count) {
    zskiplistNode *n;
    zrangespec range;
    int j = 0;

    range.min = range.max = hashslot;
    range.minex = range.maxex = 0;
    
    n = zslFirstInRange(server.cluster.slots_to_keys, range);
    while(n && n->score == hashslot && count--) {
        keys[j++] = n->obj;
        n = n->level[0].forward;
    }
    return j;
}