src/sort.c

   1 #include "redis.h"
   2 #include "pqsort.h" /* Partial qsort for SORT+LIMIT */
   3
   4 redisSortOperation *createSortOperation(int type, robj *pattern) {
   5     redisSortOperation *so = zmalloc(sizeof(*so));
   6     so->type = type;
   7     so->pattern = pattern;
   8     return so;
   9 }
  10
  11 /* Return the value associated to the key with a name obtained
  12  * substituting the first occurence of '*' in 'pattern' with 'subst'.
  13  * The returned object will always have its refcount increased by 1
  14  * when it is non-NULL. */
  15 robj *lookupKeyByPattern(redisDb *db, robj *pattern, robj *subst) {
  16     char *p, *f;
  17     sds spat, ssub;
  18     robj keyobj, fieldobj, *o;
  19     int prefixlen, sublen, postfixlen, fieldlen;
  20     /* Expoit the internal sds representation to create a sds string allocated on the stack in order to make this function faster */
  21     struct {
  22         int len;
  23         int free;
  24         char buf[REDIS_SORTKEY_MAX+1];
  25     } keyname, fieldname;
  26
  27     /* If the pattern is "#" return the substitution object itself in order
  28      * to implement the "SORT ... GET #" feature. */
  29     spat = pattern->ptr;
  30     if (spat[0] == '#' && spat[1] == '\0') {
  31         incrRefCount(subst);
  32         return subst;
  33     }
  34
  35     /* The substitution object may be specially encoded. If so we create
  36      * a decoded object on the fly. Otherwise getDecodedObject will just
  37      * increment the ref count, that we'll decrement later. */
  38     subst = getDecodedObject(subst);
  39
  40     ssub = subst->ptr;
  41     if (sdslen(spat)+sdslen(ssub)-1 > REDIS_SORTKEY_MAX) return NULL;
  42     p = strchr(spat,'*');
  43     if (!p) {
  44         decrRefCount(subst);
  45         return NULL;
  46     }
  47
  48     /* Find out if we're dealing with a hash dereference. */
  49     if ((f = strstr(p+1, "->")) != NULL) {
  50         fieldlen = sdslen(spat)-(f-spat);
  51         /* this also copies \0 character */
  52         memcpy(fieldname.buf,f+2,fieldlen-1);
  53         fieldname.len = fieldlen-2;
  54     } else {
  55         fieldlen = 0;
  56     }
  57
  58     prefixlen = p-spat;
  59     sublen = sdslen(ssub);
  60     postfixlen = sdslen(spat)-(prefixlen+1)-fieldlen;
  61     memcpy(keyname.buf,spat,prefixlen);
  62     memcpy(keyname.buf+prefixlen,ssub,sublen);
  63     memcpy(keyname.buf+prefixlen+sublen,p+1,postfixlen);
  64     keyname.buf[prefixlen+sublen+postfixlen] = '\0';
  65     keyname.len = prefixlen+sublen+postfixlen;
  66     decrRefCount(subst);
  67
  68     /* Lookup substituted key */
  69     initStaticStringObject(keyobj,((char*)&keyname)+(sizeof(struct sdshdr)));
  70     o = lookupKeyRead(db,&keyobj);
  71     if (o == NULL) return NULL;
  72
  73     if (fieldlen > 0) {
  74         if (o->type != REDIS_HASH || fieldname.len < 1) return NULL;
  75
  76         /* Retrieve value from hash by the field name. This operation
  77          * already increases the refcount of the returned object. */
  78         initStaticStringObject(fieldobj,((char*)&fieldname)+(sizeof(struct sdshdr)));
  79         o = hashTypeGet(o, &fieldobj);
  80     } else {
  81         if (o->type != REDIS_STRING) return NULL;
  82
  83         /* Every object that this function returns needs to have its refcount
  84          * increased. sortCommand decreases it again. */
  85         incrRefCount(o);
  86     }
  87
  88     return o;
  89 }
  90
  91 /* sortCompare() is used by qsort in sortCommand(). Given that qsort_r with
  92  * the additional parameter is not standard but a BSD-specific we have to
  93  * pass sorting parameters via the global 'server' structure */
  94 int sortCompare(const void *s1, const void *s2) {
  95     const redisSortObject *so1 = s1, *so2 = s2;
  96     int cmp;
  97
  98     if (!server.sort_alpha) {
  99         /* Numeric sorting. Here it's trivial as we precomputed scores */
 100         if (so1->u.score > so2->u.score) {
 101             cmp = 1;
 102         } else if (so1->u.score < so2->u.score) {
 103             cmp = -1;
 104         } else {
 105             cmp = 0;
 106         }
 107     } else {
 108         /* Alphanumeric sorting */
 109         if (server.sort_bypattern) {
 110             if (!so1->u.cmpobj || !so2->u.cmpobj) {
 111                 /* At least one compare object is NULL */
 112                 if (so1->u.cmpobj == so2->u.cmpobj)
 113                     cmp = 0;
 114                 else if (so1->u.cmpobj == NULL)
 115                     cmp = -1;
 116                 else
 117                     cmp = 1;
 118             } else {
 119                 /* We have both the objects, use strcoll */
 120                 cmp = strcoll(so1->u.cmpobj->ptr,so2->u.cmpobj->ptr);
 121             }
 122         } else {
 123             /* Compare elements directly. */
 124             cmp = compareStringObjects(so1->obj,so2->obj);
 125         }
 126     }
 127     return server.sort_desc ? -cmp : cmp;
 128 }
 129
 130 /* The SORT command is the most complex command in Redis. Warning: this code
 131  * is optimized for speed and a bit less for readability */
 132 void sortCommand(redisClient *c) {
 133     list *operations;
 134     unsigned int outputlen = 0;
 135     int desc = 0, alpha = 0;
 136     int limit_start = 0, limit_count = -1, start, end;
 137     int j, dontsort = 0, vectorlen;
 138     int getop = 0; /* GET operation counter */
 139     robj *sortval, *sortby = NULL, *storekey = NULL;
 140     redisSortObject *vector; /* Resulting vector to sort */
 141
 142     /* Lookup the key to sort. It must be of the right types */
 143     sortval = lookupKeyRead(c->db,c->argv[1]);
 144     if (sortval == NULL) {
 145         addReply(c,shared.emptymultibulk);
 146         return;
 147     }
 148     if (sortval->type != REDIS_SET && sortval->type != REDIS_LIST &&
 149         sortval->type != REDIS_ZSET)
 150     {
 151         addReply(c,shared.wrongtypeerr);
 152         return;
 153     }
 154
 155     /* Create a list of operations to perform for every sorted element.
 156      * Operations can be GET/DEL/INCR/DECR */
 157     operations = listCreate();
 158     listSetFreeMethod(operations,zfree);
 159     j = 2;
 160
 161     /* Now we need to protect sortval incrementing its count, in the future
 162      * SORT may have options able to overwrite/delete keys during the sorting
 163      * and the sorted key itself may get destroied */
 164     incrRefCount(sortval);
 165
 166     /* The SORT command has an SQL-alike syntax, parse it */
 167     while(j < c->argc) {
 168         int leftargs = c->argc-j-1;
 169         if (!strcasecmp(c->argv[j]->ptr,"asc")) {
 170             desc = 0;
 171         } else if (!strcasecmp(c->argv[j]->ptr,"desc")) {
 172             desc = 1;
 173         } else if (!strcasecmp(c->argv[j]->ptr,"alpha")) {
 174             alpha = 1;
 175         } else if (!strcasecmp(c->argv[j]->ptr,"limit") && leftargs >= 2) {
 176             limit_start = atoi(c->argv[j+1]->ptr);
 177             limit_count = atoi(c->argv[j+2]->ptr);
 178             j+=2;
 179         } else if (!strcasecmp(c->argv[j]->ptr,"store") && leftargs >= 1) {
 180             storekey = c->argv[j+1];
 181             j++;
 182         } else if (!strcasecmp(c->argv[j]->ptr,"by") && leftargs >= 1) {
 183             sortby = c->argv[j+1];
 184             /* If the BY pattern does not contain '*', i.e. it is constant,
 185              * we don't need to sort nor to lookup the weight keys. */
 186             if (strchr(c->argv[j+1]->ptr,'*') == NULL) dontsort = 1;
 187             j++;
 188         } else if (!strcasecmp(c->argv[j]->ptr,"get") && leftargs >= 1) {
 189             listAddNodeTail(operations,createSortOperation(
 190                 REDIS_SORT_GET,c->argv[j+1]));
 191             getop++;
 192             j++;
 193         } else {
 194             decrRefCount(sortval);
 195             listRelease(operations);
 196             addReply(c,shared.syntaxerr);
 197             return;
 198         }
 199         j++;
 200     }
 201
 202     /* Load the sorting vector with all the objects to sort */
 203     switch(sortval->type) {
 204     case REDIS_LIST: vectorlen = listTypeLength(sortval); break;
 205     case REDIS_SET: vectorlen =  dictSize((dict*)sortval->ptr); break;
 206     case REDIS_ZSET: vectorlen = dictSize(((zset*)sortval->ptr)->dict); break;
 207     default: vectorlen = 0; redisPanic("Bad SORT type"); /* Avoid GCC warning */
 208     }
 209     vector = zmalloc(sizeof(redisSortObject)*vectorlen);
 210     j = 0;
 211
 212     if (sortval->type == REDIS_LIST) {
 213         listTypeIterator *li = listTypeInitIterator(sortval,0,REDIS_TAIL);
 214         listTypeEntry entry;
 215         while(listTypeNext(li,&entry)) {
 216             vector[j].obj = listTypeGet(&entry);
 217             vector[j].u.score = 0;
 218             vector[j].u.cmpobj = NULL;
 219             j++;
 220         }
 221         listTypeReleaseIterator(li);
 222     } else {
 223         dict *set;
 224         dictIterator *di;
 225         dictEntry *setele;
 226
 227         if (sortval->type == REDIS_SET) {
 228             set = sortval->ptr;
 229         } else {
 230             zset *zs = sortval->ptr;
 231             set = zs->dict;
 232         }
 233
 234         di = dictGetIterator(set);
 235         while((setele = dictNext(di)) != NULL) {
 236             vector[j].obj = dictGetEntryKey(setele);
 237             vector[j].u.score = 0;
 238             vector[j].u.cmpobj = NULL;
 239             j++;
 240         }
 241         dictReleaseIterator(di);
 242     }
 243     redisAssert(j == vectorlen);
 244
 245     /* Now it's time to load the right scores in the sorting vector */
 246     if (dontsort == 0) {
 247         for (j = 0; j < vectorlen; j++) {
 248             robj *byval;
 249             if (sortby) {
 250                 /* lookup value to sort by */
 251                 byval = lookupKeyByPattern(c->db,sortby,vector[j].obj);
 252                 if (!byval) continue;
 253             } else {
 254                 /* use object itself to sort by */
 255                 byval = vector[j].obj;
 256             }
 257
 258             if (alpha) {
 259                 if (sortby) vector[j].u.cmpobj = getDecodedObject(byval);
 260             } else {
 261                 if (byval->encoding == REDIS_ENCODING_RAW) {
 262                     vector[j].u.score = strtod(byval->ptr,NULL);
 263                 } else if (byval->encoding == REDIS_ENCODING_INT) {
 264                     /* Don't need to decode the object if it's
 265                      * integer-encoded (the only encoding supported) so
 266                      * far. We can just cast it */
 267                     vector[j].u.score = (long)byval->ptr;
 268                 } else {
 269                     redisAssert(1 != 1);
 270                 }
 271             }
 272
 273             /* when the object was retrieved using lookupKeyByPattern,
 274              * its refcount needs to be decreased. */
 275             if (sortby) {
 276                 decrRefCount(byval);
 277             }
 278         }
 279     }
 280
 281     /* We are ready to sort the vector... perform a bit of sanity check
 282      * on the LIMIT option too. We'll use a partial version of quicksort. */
 283     start = (limit_start < 0) ? 0 : limit_start;
 284     end = (limit_count < 0) ? vectorlen-1 : start+limit_count-1;
 285     if (start >= vectorlen) {
 286         start = vectorlen-1;
 287         end = vectorlen-2;
 288     }
 289     if (end >= vectorlen) end = vectorlen-1;
 290
 291     if (dontsort == 0) {
 292         server.sort_desc = desc;
 293         server.sort_alpha = alpha;
 294         server.sort_bypattern = sortby ? 1 : 0;
 295         if (sortby && (start != 0 || end != vectorlen-1))
 296             pqsort(vector,vectorlen,sizeof(redisSortObject),sortCompare, start,end);
 297         else
 298             qsort(vector,vectorlen,sizeof(redisSortObject),sortCompare);
 299     }
 300
 301     /* Send command output to the output buffer, performing the specified
 302      * GET/DEL/INCR/DECR operations if any. */
 303     outputlen = getop ? getop*(end-start+1) : end-start+1;
 304     if (storekey == NULL) {
 305         /* STORE option not specified, sent the sorting result to client */
 306         addReplySds(c,sdscatprintf(sdsempty(),"*%d\r\n",outputlen));
 307         for (j = start; j <= end; j++) {
 308             listNode *ln;
 309             listIter li;
 310
 311             if (!getop) addReplyBulk(c,vector[j].obj);
 312             listRewind(operations,&li);
 313             while((ln = listNext(&li))) {
 314                 redisSortOperation *sop = ln->value;
 315                 robj *val = lookupKeyByPattern(c->db,sop->pattern,
 316                     vector[j].obj);
 317
 318                 if (sop->type == REDIS_SORT_GET) {
 319                     if (!val) {
 320                         addReply(c,shared.nullbulk);
 321                     } else {
 322                         addReplyBulk(c,val);
 323                         decrRefCount(val);
 324                     }
 325                 } else {
 326                     redisAssert(sop->type == REDIS_SORT_GET); /* always fails */
 327                 }
 328             }
 329         }
 330     } else {
 331         robj *sobj = createZiplistObject();
 332
 333         /* STORE option specified, set the sorting result as a List object */
 334         for (j = start; j <= end; j++) {
 335             listNode *ln;
 336             listIter li;
 337
 338             if (!getop) {
 339                 listTypePush(sobj,vector[j].obj,REDIS_TAIL);
 340             } else {
 341                 listRewind(operations,&li);
 342                 while((ln = listNext(&li))) {
 343                     redisSortOperation *sop = ln->value;
 344                     robj *val = lookupKeyByPattern(c->db,sop->pattern,
 345                         vector[j].obj);
 346
 347                     if (sop->type == REDIS_SORT_GET) {
 348                         if (!val) val = createStringObject("",0);
 349
 350                         /* listTypePush does an incrRefCount, so we should take care
 351                          * care of the incremented refcount caused by either
 352                          * lookupKeyByPattern or createStringObject("",0) */
 353                         listTypePush(sobj,val,REDIS_TAIL);
 354                         decrRefCount(val);
 355                     } else {
 356                         /* always fails */
 357                         redisAssert(sop->type == REDIS_SORT_GET);
 358                     }
 359                 }
 360             }
 361         }
 362         dbReplace(c->db,storekey,sobj);
 363         /* Note: we add 1 because the DB is dirty anyway since even if the
 364          * SORT result is empty a new key is set and maybe the old content
 365          * replaced. */
 366         server.dirty += 1+outputlen;
 367         touchWatchedKey(c->db,storekey);
 368         addReplySds(c,sdscatprintf(sdsempty(),":%d\r\n",outputlen));
 369     }
 370
 371     /* Cleanup */
 372     if (sortval->type == REDIS_LIST)
 373         for (j = 0; j < vectorlen; j++)
 374             decrRefCount(vector[j].obj);
 375     decrRefCount(sortval);
 376     listRelease(operations);
 377     for (j = 0; j < vectorlen; j++) {
 378         if (alpha && vector[j].u.cmpobj)
 379             decrRefCount(vector[j].u.cmpobj);
 380     }
 381     zfree(vector);
 382 }
 383
 384