Function dbMerge

src/db.cpp:376–397

Insert a key, handling duplicate keys according to fReplace */

/* Insert a key, handling duplicate keys according to fReplace */
int dbMerge(redisDb *db, sds key, robj *val, int fReplace)
{
    if (fReplace)
    {
        auto itr = db->find(key);
        if (itr == nullptr)
            return (dbAddCore(db, key, val, false /* fUpdateMvcc */) == true);

        robj_roptr old = itr.val();
        if (mvccFromObj(old) <= mvccFromObj(val))
        {
            db->dbOverwriteCore(itr, key, val, false, true);
            return true;
        }

        return false;
    }
    else
    {
        return (dbAddCore(db, key, val, true /* fUpdateMvcc */, true /* fAssumeNew */) == true);
    }
}

/* High level Set operation. This function can be used in order to set
 * a key, whatever it was existing or not, to a new object.