1.HDEL
从 key 指定的哈希集中移除指定的域。在哈希集中不存在的域将被忽略。
如果 key 指定的哈希集不存在，它将被认为是一个空的哈希集，该命令将返回0。
127.0.0.1:6379> hset myhash field1 "foo" (integer) 1 6379> hdel myhash field1 (integer) 6379>
源码解析
// t_hash.c, void hdelCommand(client *c) { robj *o; int j,deleted = 0,keyremoved = 0; if ((o = lookupKeyWriteOrReply(c,c->argv[1],shared.czero)) == NULL || checkType(c,o,OBJ_HASH)) return; 循环删除给定字段列表 for (j = 2; j < c->argc; j++) { if (hashTypeDelete(o,c->argv[j]->ptr)) { deleted++; 当没有任何元素后，直接将key删除 if (hashTypeLength(o) == ) { dbDelete(c->db,1)">1]); keyremoved = ; break; } } } if (deleted) { signalModifiedKey(c->db,1)">]); notifyKeyspaceEvent(NOTIFY_HASH,hdel",c->db->id); (keyremoved) notifyKeyspaceEvent(NOTIFY_GENERIC,1)">del],c->db->id); server.dirty += deleted; } addReplyLongLong(c,deleted); } 具体删除 field,同样区分编码类型，不同处理逻辑 /* Delete an element from a hash. * Return 1 on deleted and 0 on not found. */ int hashTypeDelete(robj *o,sds field) { int deleted = if (o->encoding == OBJ_ENCODING_ZIPLIST) { unsigned char *zl,*fptr; zl = o->ptr; fptr = ziplistIndex(zl,ZIPLIST_HEAD); if (fptr != NULL) { ziplist 删除，依次删除 field,value fptr = ziplistFind(fptr,(unsigned char*)field,sdslen(field),); NULL) { ziplistDelete 为原地删除，所以只要调用2次，即把kv删除 zl = ziplistDelete(zl,&fptr); zl = ziplistDelete(zl,1)">fptr); o->ptr = zl; deleted = ; } } } else OBJ_ENCODING_HT) { if (dictDelete((dict*)o->ptr,field) == C_OK) { deleted = ; /* Always check if the dictionary needs a resize after a delete. */ hash 删除的，可能需要进行缩容操作，这种处理方法相对特殊些 if (htNeedsResize(o->ptr)) dictResize(o->ptr); } } else { serverPanic(Unknown hash encoding); } deleted; } server.c,是否需要进行 resize int htNeedsResize(dict *dict) { long long size,used; size = dictSlots(dict); used = dictSize(dict); HASHTABLE_MIN_FILL=10,即使用率小于 1/10 时，可以进行缩容操作了 return (size && used && size > DICT_HT_INITIAL_SIZE && (used*100/size < HASHTABLE_MIN_FILL)); }
2.HEXISTS
返回hash里面field是否存在
时间复杂度：O(1)
hexists myhash field1 (integer) hexists myhash field2 (integer) 0 void hexistsCommand(client *if ((o = lookupKeyReadOrReply(c,1)">; addReply(c,hashTypeExists(o,c->argv[2]->ptr) ? shared.cone : shared.czero); }
hashTypeExists
int hashTypeExists(robj *char *vstr = NULL; unsigned int vlen = UINT_MAX; long vll = LLONG_MAX; if (hashTypeGetFromZiplist(o,field,&vstr,&vlen,&vll) == 0) return ; } if (hashTypeGetFromHashTable(o,field) != NULL) ; }
ziplist的类型判断
Get the value from a ziplist encoded hash,identified by field. * Returns -1 when the field cannot be found. int hashTypeGetFromZiplist(robj *char **vstr,1)">int *vlen,long *vll) { unsigned NULL; int ret; serverAssert(o->encoding == OBJ_ENCODING_ZIPLIST); zl = o->ptr; fptr = NULL) { fptr = ziplistFind(fptr,1)">); Grab pointer to the value (fptr points to the field) */ vptr = ziplistNext(zl,fptr); serverAssert(vptr != NULL); } } if (vptr != NULL) { ret = ziplistGet(vptr,vstr,vlen,vll); serverAssert(ret); ; } return -ziplistFindFind pointer to the entry equal to the specified entry. Skip 'skip' entries * between every comparison. Returns NULL when the field could not be found. unsigned char *ziplistFind(unsigned char *p,unsigned char *vstr,1)">int vlen,1)"> skip) { int skipcnt = ; unsigned char vencoding = long vll = while (p[0] != ZIP_END) { unsigned prevlensize,encoding,lensize,len; unsigned char *q; ZIP_DECODE_PREVLENSIZE(p,prevlensize); ZIP_DECODE_LENGTH(p + lensize; if (skipcnt == ) { Compare current entry with specified entry (ZIP_IS_STR(encoding)) { if (len == vlen && memcmp(q,vlen) == ) { p; } } { Find out if the searched field can be encoded. Note that * we do it only the first time,once done vencoding is set * to non-zero and vll is set to the integer value. */ if (vencoding == if (!zipTryEncoding(vstr,&vll,1)">vencoding)) { If the entry can't be encoded we set it to * UCHAR_MAX so that we don't retry again the next * time. vencoding = UCHAR_MAX; } Must be non-zero by now assert(vencoding); } Compare current entry with specified entry,do it only * if vencoding != UCHAR_MAX because if there is no encoding * possible for the field it can't be a valid integer. if (vencoding != UCHAR_MAX) { long ll = zipLoadInteger(q,encoding); if (ll == vll) { p; } } } Reset skip count skipcnt = skip; } { Skip entry skipcnt--; } Move to next entry p = q + len; } NULL; }hashtable类型的
Get the value from a hash table encoded hash,identified by field. * Returns NULL when the field cannot be found,otherwise the SDS value * is returned. sds hashTypeGetFromHashTable(robj *de; serverAssert(o->encoding == OBJ_ENCODING_HT); de = dictFind(o->ptr,field); if (de == NULL) dictGetVal(de); }dictFInd
dictEntry *dictFind(dict *d,const void *key) { dictEntry *he; uint64_t h,idx,table; if (dictSize(d) == return NULL; dict is empty */ (dictIsRehashing(d)) _dictRehashStep(d); h = dictHashKey(d,key); for (table = 0; table <= 1; table++) { idx = h & d->ht[table].sizemask; he = d->ht[table].table[idx]; while(he) { if (key==he->key || dictCompareKeys(d,key,he->key)) he; he = he->next; } if (!dictIsRehashing(d)) NULL; } NULL; }3.HGETALL、HKEYS、HVALS
HGetAll：返回 key 指定的哈希集中所有的字段和值。返回值中，每个字段名的下一个是它的值，所以返回值的长度是哈希集大小的两倍
时间复杂度：O(N)
HKeys:返回 key 指定的哈希集中所有字段的名字。
HVals:返回 key 指定的哈希集中所有字段的值。
时间复杂度：O(N)
Hello6379> hset myhash field2 World hkeys myhash 1) field1" 2) field2 hgetall myhash 3) 4) hvals myhash void hkeysCommand(client *c) { genericHgetallCommand(c,OBJ_HASH_KEY); } void hvalsCommand(client *void hgetallCommand(client *OBJ_HASH_VALUE); }
void genericHgetallCommand(client *c,1)"> flags) { robj *o; hashTypeIterator *hi; int length,count = resp])) == NULL || checkType(c,OBJ_HASH)) We return a map if the user requested keys and values,like in the * HGETALL case. Otherwise to use a flat array makes more sense. length = hashTypeLength(o); if (flags & OBJ_HASH_KEY && flags & OBJ_HASH_VALUE) { addReplyMapLen(c,length); } { addReplyArrayLen(c,length); } hi = hashTypeInitIterator(o); while (hashTypeNext(hi) != C_ERR) { if (flags & OBJ_HASH_KEY) { addHashIteratorCursorToReply(c,hi,OBJ_HASH_KEY); count++; } OBJ_HASH_VALUE) { addHashIteratorCursorToReply(c,OBJ_HASH_VALUE); count++; } } hashTypeReleaseIterator(hi); Make sure we returned the right number of elements. if (flags & OBJ_HASH_KEY && flags & OBJ_HASH_VALUE) count /= 2; serverAssert(count == length); }4.HLEN
返回
key指定的哈希集包含的字段的数量。hlen myhash (integer) 2 6379>
void hlenCommand(client *o; ; addReplyLongLong(c,hashTypeLength(o)); }
Return the number of elements in a hash. long hashTypeLength(const robj *o) { unsigned long length = ULONG_MAX; OBJ_ENCODING_ZIPLIST) { length = ziplistLen(o->ptr) / OBJ_ENCODING_HT) { length = dictSize((const dict*)o->ptr); } length; }
