v[3] = tryObjectEncoding(c->argv[3]);//member元素
/* If the source key does not exist return 0 */
if (srcset == NULL) {
addReply(c,shared.czero);
return;
}
/* If the source key has the wrong type, or the destination key
* is set and has the wrong type, return with an error. */
if (checkType(c,srcset,REDIS_SET) ||
(dstset && checkType(c,dstset,REDIS_SET))) return;//类型检查
/* If srcset and dstset are equal, SMOVE is a no-op */
if (srcset == dstset) {//source与dest相同
addReply(c,shared.cone);
return;
}
/* If the element cannot be removed from the src set, return 0. */
if (!setTypeRemove(srcset,ele)) {//从源集合中删除member元素
addReply(c,shared.czero);
return;
}
notifyKeyspaceEvent(REDIS_NOTIFY_SET,"srem",c->argv[1],c->db->id);
/* Remove the src set from the database when empty */
if (setTypeSize(srcset) == 0) {//移除member元素后，源集合为空，删除
dbDelete(c->db,c->argv[1]);
notifyKeyspaceEvent(REDIS_NOTIFY_GENERIC,"del",c->argv[1],c->db->id);
}
signalModifiedKey(c->db,c->argv[1]);
signalModifiedKey(c->db,c->argv[2]);
server.dirty++;
/* Create the destination set when it doesn't exist */
if (!dstset) {//目标集合不存在，则新建
dstset = setTypeCreate(ele);
dbAdd(c->db,c->argv[2],dstset);
}
/* An extra key has changed when ele was successfully added to dstset */
if (setTypeAdd(dstset,ele)) {//添加member元素到目标集合
server.dirty++;
notifyKeyspaceEvent(REDIS_NOTIFY_SET,"sadd",c->argv[2],c->db->id);
}
addReply(c,shared.cone);
}
SPOP
SPOP key
移除并返回集合key中的一个随机元素。
时间复杂度:O(1)
由于是随机删除一个元素，那么对复制与AOF肯定有影响，因此该操作后，需要将该指令改变为SREM即将该元素删除，参考rewriteClientCommandVector函数。
SRANDMEMBER
SRANDMEMBER key [count]
[count]参数可选,如果没有count,那么返回集合中的一个随机元素。
如果count为正数，且小于集合元素个数，那么命令返回一个包含count个元素的数组，数组中的元素各不相同,如果count大于等于集合基数，那么返回整个集合;如果 count 为负数，那么命令返回一个数组，数组中的元素可能会重复出现多次，而数组的长度为count的绝对值。
SREM
SREM key member [member ...]
移除集合key中的一个或多个member元素，不存在的member元素会被忽略。
集合求交算法
集合求交的指令有两个:SINTER与SINTERSTORE
SINTER key [key ...]
返回所有给定集合的交集,不存在的 key 被视为空集,当给定集合当中有一个空集时，结果也为空集.
时间复杂度: O(N * M)，N 为给定集合中元素数目最小的集合，M 为给定集合的个数
SINTERSTORE destination key [key ...]
与SINTER指令类似,不同的仅仅将结果集存储到目标集合destination中,如果集合destination已存在,那么将其覆盖
void sinterGenericCommand(redisClient *c, robj **setkeys, unsigned long setnum, robj *dstkey) {
robj **sets = zmalloc(sizeof(robj*)*setnum);
setTypeIterator *si;//迭代器
robj *eleobj, *dstset = NULL;
int64_t intobj;
void *replylen = NULL;
unsigned long j, cardinality = 0;
int encoding;
for (j = 0; j < setnum; j++) {//得到所有的集合
robj *setobj = dstkey
lookupKeyWrite(c->db,setkeys[j]) :
lookupKeyRead(c->db,setkeys[j]);
if (!setobj) {//任何一个集合不存在，那么总的交集就为空
zfree(sets);
if (dstkey) {
if (dbDelete(c->db,dstkey)) {
signalModifiedKey(c->db,dstkey);
server.dirty++;
}
addReply(c,shared.czero);
} else {
addReply(c,shared.emptymultibulk);
}
return;
}
if (checkType(c,setobj,REDIS_SET)) {//类型检查
zfree(sets);
return;
}
sets[j] = setobj;
}
/* Sort sets from the smallest to largest, this will improve our
* algorithm's performance */
//按照集合元素个数从小到大排序
qsort(sets,setnum,sizeof(robj*),qsortCompareSetsByCardinality);
/* The first thing we should output is the total number of elements...
* since this is a multi-bulk write, but at this stage we don't know
* the intersection set size, so we use a trick, append an empty object
* to the output list and sav