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语法：

keys pattern

返回所有符合pattern的key

支持 glob-style patterns:

• h?llo matches hello, hallo and hxllo
• h*llo matches hllo and heeeello
• h[ae]llo matches hello and hallo, but not hillo
• h[^e]llo matches hallo, hbllo, ... but not hello
• h[a-b]llo matches hallo and hbllo

源码分析

void keysCommand(client *c)
{dictIterator *di;dictEntry *de;// 获取当前的匹配模式sds pattern = c->argv[1]->ptr;int plen = sdslen(pattern), allkeys;unsigned long numkeys = 0;void *replylen = addReplyDeferredLen(c);// 获取数据字典的迭代器di = dictGetSafeIterator(c->db->dict);// 判断是否获取全部allkeys = (pattern[0] == '*' && plen == 1);// 遍历迭代器while ((de = dictNext(di)) != NULL){// 获取当前遍历的keysds key = dictGetKey(de);robj *keyobj;// 如果是获取全部key 或是 当前的key符合匹配模式if (allkeys || stringmatchlen(pattern, plen, key, sdslen(key), 0)){// 当前当前的key转换成robj对象keyobj = createStringObject(key, sdslen(key));// 如果key没有过期，则加入响应缓存if (!keyIsExpired(c->db, keyobj)){addReplyBulk(c, keyobj);numkeys++;}decrRefCount(keyobj);}}// 遍历结束，释放对象dictReleaseIterator(di);setDeferredArrayLen(c, replylen, numkeys);
}

上面的源码中可以看到：

1. keys 需要遍历全部key
2. 遍历的所有的key都要和pattern 进行比较

所以在生产环境中，要很谨慎使用keys 命令，避免遍历过多的key而阻塞。