【Redis学习笔记】2018-07-10 Redis指令学习3

摘要：顺风车运营研发团队闫昌一使用方式使用描述将元素从集合移动到集合是原子性操作如果集合不存在或不包含指定的元素，则命令不执行任何操作，仅返回。否则，元素从集合中被移除，并添加到集合中去当集合已经包含元素时，命令只是简单地将集合中的元素删除。

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;
}