redis源码从main开始7

在redis源码从main开始6中看完了客户端发来一个命令在redis中的执行流程，本章我们看一个经常会引起性能问题的命令keys，keys命令用来查找匹配模式的键，下面我们来看看，为什么在数据量巨大的redis中使用keys命令会使得redis无法处理其他请求。具体原因在于，while((de = dictNext(di)) != NULL) 会遍历查找的所有键，判断是否可以匹配

void keysCommand(redisClient *c) {
    dictIterator *di;
    dictEntry *de;

    // 需要匹配的规则
    sds pattern = c->argv[1]->ptr;

    int plen = sdslen(pattern), allkeys;
    unsigned long numkeys = 0;
    void *replylen = addDeferredMultiBulkLength(c);

    // 安全模式的迭代器
    di = dictGetSafeIterator(c->db->dict);
    // 是全部key都匹配 keys * 命令
    allkeys = (pattern[0] == '*' && pattern[1] == '\0');
    while((de = dictNext(di)) != NULL) {
        sds key = dictGetKey(de);
        robj *keyobj;

        // 是所有key都符合, 或者处理匹配
        if (allkeys || stringmatchlen(pattern,plen,key,sdslen(key),0)) {

            // 创建匹配到的键名字符串对象
            keyobj = createStringObject(key,sdslen(key));

            // 判断键是否过期了==0是键还存在,会添加到回复中
            if (expireIfNeeded(c->db,keyobj) == 0) {
                addReplyBulk(c,keyobj);
                numkeys++;
            }

            decrRefCount(keyobj);
        }
    }
    dictReleaseIterator(di);

    setDeferredMultiBulkLength(c,replylen,numkeys);
}


/* Glob-style pattern matching. */
int stringmatchlen(const char *pattern, int patternLen,
        const char *string, int stringLen, int nocase)
{
    while(patternLen) {
        switch(pattern[0]) {
        case '*':
            while (pattern[1] == '*') {
                pattern++;
                patternLen--;
            }
            if (patternLen == 1)
                return 1; /* match */
            while(stringLen) {
                if (stringmatchlen(pattern+1, patternLen-1,
                            string, stringLen, nocase))
                    return 1; /* match */
                string++;
                stringLen--;
            }
            return 0; /* no match */
            break;
        case '?':
            if (stringLen == 0)
                return 0; /* no match */
            string++;
            stringLen--;
            break;
        case '[':
        {
            int not, match;

            pattern++;
            patternLen--;
            not = pattern[0] == '^';
            if (not) {
                pattern++;
                patternLen--;
            }
            match = 0;
            while(1) {
                if (pattern[0] == '\\') {
                    pattern++;
                    patternLen--;
                    if (pattern[0] == string[0])
                        match = 1;
                } else if (pattern[0] == ']') {
                    break;
                } else if (patternLen == 0) {
                    pattern--;
                    patternLen++;
                    break;
                } else if (pattern[1] == '-' && patternLen >= 3) {
                    int start = pattern[0];
                    int end = pattern[2];
                    int c = string[0];
                    if (start > end) {
                        int t = start;
                        start = end;
                        end = t;
                    }
                    if (nocase) {
                        start = tolower(start);
                        end = tolower(end);
                        c = tolower(c);
                    }
                    pattern += 2;
                    patternLen -= 2;
                    if (c >= start && c <= end)
                        match = 1;
                } else {
                    if (!nocase) {
                        if (pattern[0] == string[0])
                            match = 1;
                    } else {
                        if (tolower((int)pattern[0]) == tolower((int)string[0]))
                            match = 1;
                    }
                }
                pattern++;
                patternLen--;
            }
            if (not)
                match = !match;
            if (!match)
                return 0; /* no match */
            string++;
            stringLen--;
            break;
        }
        case '\\':
            if (patternLen >= 2) {
                pattern++;
                patternLen--;
            }
            /* fall through */
        default:
            if (!nocase) {
                if (pattern[0] != string[0])
                    return 0; /* no match */
            } else {
                if (tolower((int)pattern[0]) != tolower((int)string[0]))
                    return 0; /* no match */
            }
            string++;
            stringLen--;
            break;
        }
        pattern++;
        patternLen--;
        if (stringLen == 0) {
            while(*pattern == '*') {
                pattern++;
                patternLen--;
            }
            break;
        }
    }
    if (patternLen == 0 && stringLen == 0)
        return 1;
    return 0;
}

基于版本3.0.0版本,点击下载https://download.redis.io/releases/redis-3.0.0.tar.gz

本文地址，https://www.ccagml.com/?p=390