Function dbAsyncDelete

app/redis-6.2.6/src/lazyfree.c:146–187

 * will be reclaimed in a different bio.c thread. */
#define LAZYFREE_THRESHOLD 64
int dbAsyncDelete(redisDb *db, robj *key) {
    /* Deleting an entry from the expires dict will not free the sds of
     * the key, because it is shared with the main dictionary. */
    if (dictSize(db->expires) > 0) dictDelete(db->expires,key->ptr);

    /* If the value is composed of a few allocations, to free in a lazy way
     * is actually just slower... So under a certain limit we just free
     * the object synchronously. */
    dictEntry *de = dictUnlink(db->dict,key->ptr);
    if (de) {
        robj *val = dictGetVal(de);

        /* Tells the module that the key has been unlinked from the database. */
        moduleNotifyKeyUnlink(key,val);

        size_t free_effort = lazyfreeGetFreeEffort(key,val);

        /* If releasing the object is too much work, do it in the background
         * by adding the object to the lazy free list.
         * Note that if the object is shared, to reclaim it now it is not
         * possible. This rarely happens, however sometimes the implementation
         * of parts of the Redis core may call incrRefCount() to protect
         * objects, and then call dbDelete(). In this case we'll fall
         * through and reach the dictFreeUnlinkedEntry() call, that will be
         * equivalent to just calling decrRefCount(). */
        if (free_effort > LAZYFREE_THRESHOLD && val->refcount == 1) {
            atomicIncr(lazyfree_objects,1);
            bioCreateLazyFreeJob(lazyfreeFreeObject,1, val);
            dictSetVal(db->dict,de,NULL);
        }
    }

    /* Release the key-val pair, or just the key if we set the val
     * field to NULL in order to lazy free it later. */
    if (de) {
        dictFreeUnlinkedEntry(db->dict,de);
        if (server.cluster_enabled) slotToKeyDel(key->ptr);
        return 1;
    } else {
        return 0;
    }
}

/* Free an object, if the object is huge enough, free it in async way. */
void freeObjAsync(robj *key, robj *obj) {