Redis源码分析--lookupKey函数查看value值

最新推荐文章于 2024-07-31 16:08:46 发布

unix21

最新推荐文章于 2024-07-31 16:08:46 发布

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分类专栏： Redis

本文链接：https://blog.youkuaiyun.com/unix21/article/details/10132545

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本文详细剖析了Redis中lookupKey函数的作用，通过GDB调试展示了如何查看键值对中的value，并跟踪了从lookupKey到处理命令的调用流程。

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lookupKey函数查看value值

robj *lookupKey(redisDb *db, robj *key) {
    dictEntry *de = dictFind(db->dict,key->ptr);
    if (de) {
        robj *val = dictGetVal(de);

        /* Update the access time for the ageing algorithm.
         * Don't do it if we have a saving child, as this will trigger
         * a copy on write madness. */
        if (server.rdb_child_pid == -1 && server.aof_child_pid == -1)
            val->lru = server.lruclock;
        return val;
    } else {
        return NULL;
    }
}

数据类型，ptr指针指向的就是具体value，需要强制转换

typedef struct redisObject {
    unsigned type:4;
    unsigned notused:2;     /* Not used */
    unsigned encoding:4;
    unsigned lru:22;        /* lru time (relative to server.lruclock) */
    int refcount;
    void *ptr;
} robj;

(gdb) p (char *)val->ptr
$20 = 0x7ffff7435728 "http://blog.youkuaiyun.com/unix21"
(gdb) p (char *)(*(robj *)(de->v->val))->ptr
$21 = 0x7ffff7435728 "http://blog.youkuaiyun.com/unix21"
(gdb) bt
#0 lookupKey (db=0x7ffff7515300, key=0x7ffff7486330) at db.c:51
#1 0x000000000042bee7 in lookupKeyRead (db=0x7ffff7515300, key=0x7ffff7486330) at db.c:62
#2 0x000000000042bf81 in lookupKeyReadOrReply (c=0x7ffff7531000, key=0x7ffff7486330, reply=0x7ffff7410e50) at db.c:76
#3 0x0000000000433519 in getGenericCommand (c=0x7ffff7531000) at t_string.c:145
#4 0x0000000000433588 in getCommand (c=0x7ffff7531000) at t_string.c:158
#5 0x000000000041ba15 in call (c=0x7ffff7531000, flags=7) at redis.c:1599
#6 0x000000000041c12c in processCommand (c=0x7ffff7531000) at redis.c:1774
#7 0x000000000042874a in processInputBuffer (c=0x7ffff7531000) at networking.c:1013
#8 0x00000000004289f5 in readQueryFromClient (el=0x7ffff7458150, fd=9, privdata=0x7ffff7531000, mask=1) at networking.c:1076
#9 0x0000000000415f5d in aeProcessEvents (eventLoop=0x7ffff7458150, flags=3) at ae.c:382
#10 0x00000000004160f2 in aeMain (eventLoop=0x7ffff7458150) at ae.c:425
#11 0x000000000041e8a7 in main (argc=1, argv=0x7fffffffe578) at redis.c:2721