顺风车运营研发团队 闫昌
一. smove

使用方式: smove source destination member
使用描述: 将member元素从source集合移动到destination集合
smove是原子性操作
如果 source 集合不存在或不包含指定的 member 元素，则 SMOVE 命令不执行任何操作，仅返回 0 。否则， member 元素从 source 集合中被移除，并添加到 destination 集合中去
当 destination 集合已经包含 member 元素时， SMOVE 命令只是简单地将 source 集合中的 member 元素删除。
当 source 或 destination 不是集合类型时，返回一个错误。
源码分析:

void smoveCommand(client *c) {
    robj *srcset, *dstset, *ele;
    srcset = lookupKeyWrite(c->db,c->argv[1]);
    dstset = lookupKeyWrite(c->db,c->argv[2]);
    ele = c->argv[3];
 
    if (srcset == NULL) {//如果source不存在, 则直接返回
        addReply(c,shared.czero);
        return;
    }
 
    if (checkType(c,srcset,OBJ_SET) ||
        (dstset && checkType(c,dstset,OBJ_SET))) return;//source和dest必须全部为set类型, 否则退出
 
    if (srcset == dstset) {//如果source和dest相同, 则直接返回
        addReply(c,setTypeIsMember(srcset,ele->ptr) ?
            shared.cone : shared.czero);
        return;
    }
 
    if (!setTypeRemove(srcset,ele->ptr)) {//如果source移除失败, 则直接返回
        addReply(c,shared.czero);
        return;
    }
    notifyKeyspaceEvent(NOTIFY_SET,"srem",c->argv[1],c->db->id);
 
    if (setTypeSize(srcset) == 0) {//如果移除一个元素之后, source已经为空, 则将source删除
        dbDelete(c->db,c->argv[1]);
        notifyKeyspaceEvent(NOTIFY_GENERIC,"del",c->argv[1],c->db->id);
    }
 
    if (!dstset) {//如果dest为空, 需要先将dest创建出来
        dstset = setTypeCreate(ele->ptr);
        dbAdd(c->db,c->argv[2],dstset);
    }
 
    signalModifiedKey(c->db,c->argv[1]);
    signalModifiedKey(c->db,c->argv[2]);
    server.dirty++;
 
    if (setTypeAdd(dstset,ele->ptr)) {//将元素添加到dest当中
        server.dirty++;
        notifyKeyspaceEvent(NOTIFY_SET,"sadd",c->argv[2],c->db->id);
    }
    addReply(c,shared.cone);
}

二. spop

使用方式spop key [count]
从设置值存储中移除并返回一个或多个随机key
源码分析: count=0的情况

void spopCommand(client *c) {
    robj *set, *ele, *aux;
    sds sdsele;
    int64_t llele;
    int encoding;
 
    if (c->argc == 3) {
        spopWithCountCommand(c);
        return;
    } else if (c->argc > 3) {
        addReply(c,shared.syntaxerr);
        return;
    }
 
    if ((set = lookupKeyWriteOrReply(c,c->argv[1],shared.nullbulk)) == NULL ||
        checkType(c,set,OBJ_SET)) return;
 
    /**
        获取随机元素算法:
        1. 如果是hash类型, 获取hash key
           1.1 正在rehash: 则获取  rehashidx + random()%(ht[0]+ht[1]-rehashidx)   //此时key可能在ht[0]也可能在ht[1]中, 但一但在rehashidx之后
           1.2 没有在rehash, 直接: random() % ht[0].length
        2. 如果是整数集合类型: rand()%length
            
    */
    encoding = setTypeRandomElement(set,&sdsele,&llele);//获取随机的一个元素
 
    if (encoding == OBJ_ENCODING_INTSET) {
        ele = createStringObjectFromLongLong(llele);
        set->ptr = intsetRemove(set->ptr,llele,NULL);//删除这个元素
    } else {
        ele = createStringObject(sdsele,sdslen(sdsele));
        setTypeRemove(set,ele->ptr);//删除这个元素
    }
 
    notifyKeyspaceEvent(NOTIFY_SET,"spop",c->argv[1],c->db->id);
 
    aux = createStringObject("SREM",4);
    rewriteClientCommandVector(c,3,aux,c->argv[1],ele);
    decrRefCount(aux);
 
    addReplyBulk(c,ele);
    decrRefCount(ele);
 
    if (setTypeSize(set) == 0) {//如果set已经为空, 则需要删除set集合
        dbDelete(c->db,c->argv[1]);
        notifyKeyspaceEvent(NOTIFY_GENERIC,"del",c->argv[1],c->db->id);
    }
 
    signalModifiedKey(c->db,c->argv[1]);
    server.dirty++;
}

count不为0的情况:

当count数量大于set的个数时, 直接返回所有的值, 并删除set
size-count=remining, 当remining*5>count时, 循环count次, 每次随机弹出一个key
当remining<=5时, 循环remining次, 随机弹出一个值并压入到一个新的set中, 最后将这个新的set覆盖原来的set

void spopWithCountCommand(client *c) {
    long l;
    unsigned long count, size;
    robj *set;
 
    if (getLongFromObjectOrReply(c,c->argv[2],&l,NULL) != C_OK) return;
    if (l >= 0) {
        count = (unsigned long) l;
    } else {
        addReply(c,shared.outofrangeerr);
        return;
    }
 
    if ((set = lookupKeyReadOrReply(c,c->argv[1],shared.emptymultibulk))
        == NULL || checkType(c,set,OBJ_SET)) return;
 
    if (count == 0) {
        addReply(c,shared.emptymultibulk);
        return;
    }
 
    size = setTypeSize(set);
 
    notifyKeyspaceEvent(NOTIFY_SET,"spop",c->argv[1],c->db->id);
    server.dirty += count;
 
    /* CASE 1:
     * 当count数量大于set的数量, 则直接将set的所有元素都返回, 并删除set */
    if (count >= size) {
        sunionDiffGenericCommand(c,c->argv+1,1,NULL,SET_OP_UNION);//获取集合中的所有值
 
        dbDelete(c->db,c->argv[1]);
        notifyKeyspaceEvent(NOTIFY_GENERIC,"del",c->argv[1],c->db->id);
 
        rewriteClientCommandVector(c,2,shared.del,c->argv[1]);
        signalModifiedKey(c->db,c->argv[1]);
        server.dirty++;
        return;
    }
 
  
    robj *propargv[3];
    propargv[0] = createStringObject("SREM",4);
    propargv[1] = c->argv[1];
    addReplyMultiBulkLen(c,count);
 
    /* Common iteration vars. */
    sds sdsele;
    robj *objele;
    int encoding;
    int64_t llele;
    unsigned long remaining = size-count; /* Elements left after SPOP. */
 
    /*当删除count个元素后, 剩下的元素个数*5大于count时, 需要循环count次, 每次随机pop出一个元素*/
    if (remaining*SPOP_MOVE_STRATEGY_MUL > count) {
        while(count--) {
            /* Emit and remove. */
            encoding = setTypeRandomElement(set,&sdsele,&llele);//获取随机的一个元素
            if (encoding == OBJ_ENCODING_INTSET) {
                addReplyBulkLongLong(c,llele);
                objele = createStringObjectFromLongLong(llele);
                set->ptr = intsetRemove(set->ptr,llele,NULL);//删除随机出来的元素
            } else {
                addReplyBulkCBuffer(c,sdsele,sdslen(sdsele));
                objele = createStringObject(sdsele,sdslen(sdsele));
                setTypeRemove(set,sdsele);
            }
 
            /* Replicate/AOF this command as an SREM operation */
            propargv[2] = objele;
            alsoPropagate(server.sremCommand,c->db->id,propargv,3,
                PROPAGATE_AOF|PROPAGATE_REPL);
            decrRefCount(objele);
        }
    } else {
    /* 否则循环remining次, 将pop出来的元素赋值给新的set, 最后将新的set覆盖原来的set值 */
        robj *newset = NULL;
 
        /* Create a new set with just the remaining elements. */
        while(remaining--) {
            encoding = setTypeRandomElement(set,&sdsele,&llele);
            if (encoding == OBJ_ENCODING_INTSET) {
                sdsele = sdsfromlonglong(llele);
            } else {
                sdsele = sdsdup(sdsele);
            }
            if (!newset) newset = setTypeCreate(sdsele);
            setTypeAdd(newset,sdsele);
            setTypeRemove(set,sdsele);
            sdsfree(sdsele);
        }
 
 
        incrRefCount(set); /* Protect the old set value. */
        dbOverwrite(c->db,c->argv[1],newset);//将旧的set用新的set来覆盖
 
        /* Tranfer the old set to the client and release it. */
        setTypeIterator *si;
        si = setTypeInitIterator(set);
        while((encoding = setTypeNext(si,&sdsele,&llele)) != -1) {
            if (encoding == OBJ_ENCODING_INTSET) {
                addReplyBulkLongLong(c,llele);
                objele = createStringObjectFromLongLong(llele);
            } else {
                addReplyBulkCBuffer(c,sdsele,sdslen(sdsele));
                objele = createStringObject(sdsele,sdslen(sdsele));
            }
 
            /* Replicate/AOF this command as an SREM operation */
            propargv[2] = objele;
            alsoPropagate(server.sremCommand,c->db->id,propargv,3,
                PROPAGATE_AOF|PROPAGATE_REPL);
            decrRefCount(objele);
        }
        setTypeReleaseIterator(si);
        decrRefCount(set);
    }
 
    decrRefCount(propargv[0]);
    preventCommandPropagation(c);
    signalModifiedKey(c->db,c->argv[1]);
    server.dirty++;
}

三. sismember

使用方式: sismember key member
判断member元素是否是集合key的成员
源码分析:

int setTypeIsMember(robj *subject, sds value) {
    long long llval;
    if (subject->encoding == OBJ_ENCODING_HT) {
        return dictFind((dict*)subject->ptr,value) != NULL;//从字典中查找
    } else if (subject->encoding == OBJ_ENCODING_INTSET) {
        if (isSdsRepresentableAsLongLong(value,&llval) == C_OK) {
            return intsetFind((intset*)subject->ptr,llval);//从整数集合中查找
        }
    } else {
        serverPanic("Unknown set encoding");
    }
    return 0;
}

因为整数集合中的元素是按从小到大有序排列的, 所以用二分法查找即可找出

static uint8_t intsetSearch(intset *is, int64_t value, uint32_t *pos) {
    int min = 0, max = intrev32ifbe(is->length)-1, mid = -1;
    int64_t cur = -1;
 
    if (intrev32ifbe(is->length) == 0) {//如果集合长度为0, 则直接返回
        if (pos) *pos = 0;
        return 0;
    } else {
        if (value > _intsetGet(is,intrev32ifbe(is->length)-1)) {//如果value大于整数集合的最大值, 则直接返回
            if (pos) *pos = intrev32ifbe(is->length);
            return 0;
        } else if (value < _intsetGet(is,0)) {//如果value小于整数集合的最小值, 则直接返回
            if (pos) *pos = 0;
            return 0;
        }
    }
 
    while(max >= min) {//二分法查找
        mid = ((unsigned int)min + (unsigned int)max) >> 1;
        cur = _intsetGet(is,mid);//整数集合中的数组contents是以char来存储的值, 但整数集合有int16, int32, int64三种值, 所以要找值时, 需要根据偏移量和长度来获取正确的值
        if (value > cur) {
            min = mid+1;
        } else if (value < cur) {
            max = mid-1;
        } else {
            break;
        }
    }
 
    if (value == cur) {
        if (pos) *pos = mid;
        return 1;
    } else {
        if (pos) *pos = min;
        return 0;
    }
}
static int64_t _intsetGet(intset *is, int pos) {
    return _intsetGetEncoded(is,pos,intrev32ifbe(is->encoding));
}
 
static int64_t _intsetGetEncoded(intset *is, int pos, uint8_t enc) {
    int64_t v64;
    int32_t v32;
    int16_t v16;
 
    if (enc == INTSET_ENC_INT64) {
        memcpy(&v64,((int64_t*)is->contents)+pos,sizeof(v64));//需要根据偏移量(pos), 和长度来获取到正确的值
        memrev64ifbe(&v64);
        return v64;
    } else if (enc == INTSET_ENC_INT32) {
        memcpy(&v32,((int32_t*)is->contents)+pos,sizeof(v32));
        memrev32ifbe(&v32);
        return v32;
    } else {
        memcpy(&v16,((int16_t*)is->contents)+pos,sizeof(v16));
        memrev16ifbe(&v16);
        return v16;
    }
}

四. smembers

执行方式: smembers key
返回集合key中的所有成员
不存在的key被视为空集合
smembers底层调用sinterGenericCommand函数, 即将所有集合(现在只有一个)取交集

void sinterGenericCommand(client *c, robj **setkeys,
                          unsigned long setnum, robj *dstkey) {
    robj **sets = zmalloc(sizeof(robj*)*setnum);
    setTypeIterator *si;
    robj *dstset = NULL;
    sds elesds;
    int64_t intobj;
    void *replylen = NULL;
    unsigned long j, cardinality = 0;
    int encoding;
 
    for (j = 0; j < setnum; j++) {//setnum的值为1, 这个for循环只会执行一次
        robj *setobj = dstkey ?
            lookupKeyWrite(c->db,setkeys[j]) :
            lookupKeyRead(c->db,setkeys[j]);
        if (!setobj) {
            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,OBJ_SET)) {
            zfree(sets);
            return;
        }
        sets[j] = setobj;//将集合赋值给新的集合sets[0]
    }
 
    qsort(sets,setnum,sizeof(robj*),qsortCompareSetsByCardinality);
 
 
    if (!dstkey) {
        replylen = addDeferredMultiBulkLength(c);
    } else {
        /* If we have a target key where to store the resulting set
         * create this key with an empty set inside */
        dstset = createIntsetObject();
    }
 
 
    si = setTypeInitIterator(sets[0]);
    while((encoding = setTypeNext(si,&elesds,&intobj)) != -1) {
        ...
        ...
 
        /* Only take action when all sets contain the member */
        if (j == setnum) {
            if (!dstkey) {//while循环set, 将每次遍历取出的值返回给客户端
                if (encoding == OBJ_ENCODING_HT)
                    addReplyBulkCBuffer(c,elesds,sdslen(elesds));
                else
                    addReplyBulkLongLong(c,intobj);
                cardinality++;
            } else {
               ...
            }
        }
    }
    setTypeReleaseIterator(si);
 
    if (dstkey) {
       ......
    } else {
        setDeferredMultiBulkLength(c,replylen,cardinality);
    }
    zfree(sets);
}

五. srandmember

同spop命令, 同样可以接受多个count, 它与spop的区别为srandmember不会删除元素值, spop会删除元素值

六. srem

使用方式 srem key member [member ….]
移除集合中的一个或多个member元素, 不存在的member元素会被忽略

源码分析:

void sremCommand(client *c) {
    robj *set;
    int j, deleted = 0, keyremoved = 0;
 
    if ((set = lookupKeyWriteOrReply(c,c->argv[1],shared.czero)) == NULL ||
        checkType(c,set,OBJ_SET)) return;
 
    for (j = 2; j < c->argc; j++) {//可以删除多个元素
        if (setTypeRemove(set,c->argv[j]->ptr)) {
            deleted++;
            if (setTypeSize(set) == 0) {
                dbDelete(c->db,c->argv[1]);
                keyremoved = 1;
                break;
            }
        }
    }
    if (deleted) {
        signalModifiedKey(c->db,c->argv[1]);
        notifyKeyspaceEvent(NOTIFY_SET,"srem",c->argv[1],c->db->id);
        if (keyremoved)
            notifyKeyspaceEvent(NOTIFY_GENERIC,"del",c->argv[1],
                                c->db->id);
        server.dirty += deleted;
    }
    addReplyLongLong(c,deleted);
}
int setTypeRemove(robj *setobj, sds value) {
    long long llval;
    if (setobj->encoding == OBJ_ENCODING_HT) {
        if (dictDelete(setobj->ptr,value) == DICT_OK) {//从字典中删除
            if (htNeedsResize(setobj->ptr)) dictResize(setobj->ptr);
            return 1;
        }
    } else if (setobj->encoding == OBJ_ENCODING_INTSET) {
        if (isSdsRepresentableAsLongLong(value,&llval) == C_OK) {
            int success;
            setobj->ptr = intsetRemove(setobj->ptr,llval,&success);//从整数集合中删除
            if (success) return 1;
        }
    } else {
        serverPanic("Unknown set encoding");
    }
    return 0;
}