你们应该两人一组去问路。
我故意拔掉主机与交换机之间的一根 FC电缆，从而中断其中一条访问路径。
I purposely interrupt one of the access paths by pulling off an FC cable between the host and switch.
想象一下，当一位游客走近你问路时，你正在当地的城市公园里散步。
Imagine that you are taking a walk in your local city park when a tourist approaches you asking for directions.
我有点迷路了，不得不向一个陌生人问路，但我还是走到了这里。
I got a bit lost and I had to ask a stranger, but I got here eventually.
这里有一些关于如何在国外问路的建议。
Here is some advice on how to ask the way in a foreign country.
大多数女人不知道，如果男人独自开着一辆车，他也许会停下来问路。
Most women do not know that if a man is driving in the car alone, he'd probably stop and ask directions.
因此，其中一条访问路径的中断不会影响从主机发起的存储访问。
So, any interruption to one of the access path does not affect storage access from the host.
然后，我故意拔掉主机与交换机之间的一根 FC电缆，以中断其中一条访问路径。
Then I purposely interrupt one of the access paths by pulling off an FC cable between the host and switch.
这就说明我可能有一个低效的访问路径，DB 2读取的数据比应该读取的数据更多。
This tells me that I may have an inefficient access path, where DB2 reads more data than it should.
如果您和DB2认为的最佳可用访问路径是一致的，但是这个路径不能提供让人满意的性能，那么需要向 DB2提供新的访问路径选择。
When you and DB2 agree If you and DB2 agree on the best available access path but that path does not deliver satisfactory performance, you need to provide DB2 with a new access path choice.
正如您马上就会看到的，DB 2可以使用这两个索引来为我们的查询产生一个高效的访问路径。
As you'll see shortly, DB2 can use both of these indexes to generate an efficient access path for our query.
想象一下，如果你可以过目不忘，你就可以不必再去问路了。
Imagine if you could look at something once and remember it forever.
对于带变量的sql语句，优化器会使用一个默认过滤因子在绑定时确定最佳访问路径。
For SQL statements with variables, the optimizer USES a default filter factor to determine the best access path at bind time.
然而，对于此示例则选择了一个不同的访问路径，如图7所示。
However, for this example a different access path is selected, which is shown in Figure 7.
我们以前问路的回答都是一直走,走到第几个路口向左拐或者向右拐,然而在现实生活中, 答案根本没有这么简单, 往往是九转十八弯.
In the past when we learnt how to ask the way, the answer always tended to be: Go along this road and turn left in the second turning, or so. But in real life, it is not that simple.
因此，如果优化器的估计是准确的，则此访问路径应该是一个非常有效的访问路径。
Therefore, if the optimizer's estimate is accurate, this access path should be a very efficient access path.
因为其是一个唯一索引扫描，所以在访问路径图中不显示FETCH或表节点。
There is no FETCH or table node shown in the access path graph because it is an index-only scan.
每天或许都会发生这样的情景：当你走在街上，一个看起来很迷惑的人拿着一张地图把你拦下，并向你问路。
It happens every day: you're walking down the street and someone holding a map and looking baffled stops you and asks for directions.
为简单起见，本文引用了一种满足sql语句的流行方法作为访问路径。
For simplicity, this article refers to a particular way of satisfying an SQL statement as the access path.
恰当的访问路径意味着一个索引可用并且已使用，所以该索引能够方便地对该数据进行访问。
An appropriate access path means that an index is available and used so that the index drives the access to the data.
不一致的统计数据还会误导优化器选择糟糕的访问路径。
The inconsistent statistics may also mislead the optimizer into choosing a bad access path.
本节的其余部分再一次以数据流的观点向您介绍访问路径图以便您可以在查询执行的性能方面获得充分的理解。
The rest of this section takes you through the access path graph one more time from the data flow perspective so that you can gain a full understanding of the performance aspect of query execution.
对于一个给定的sql语句，往往有多个访问路径选择，而不同的访问路径具有不同的性能特点。
For a given SQL statement, there are often multiple access path choices, and the different access paths usually have different performance characteristics.
从性能的角度来看，一个良好表现的访问路径相对于最终的结果集应该触及最少的数据量。
From a performance point of view, a good performing access path should touch the least amount of data with respect to the final result set.
还有，在选择访问路径之前，优化器首先会执行一系列查询转换以增加可用访问路径的数目。
Also, before selecting the access path, the optimizer first performs a series of query transformations to increase the number of access paths available.
具体表现就是提前执行一些工作，比如确定数据库访问路径。
It does this by performing some work ahead of time, such as determining the database access path.
当弗洛伊德先生被一张火车时刻表搞得不知所措，或是他明明已经站在咖啡店门口了，却还要询问路人那里有咖啡店，都让人觉得他就和普宁教授一样可爱。
Freud is as lovable as Professor Pnin when he pores hopelessly over a train schedule or asks a stranger the way to a coffee shop while standing in front of a coffee shop.
有一些很有趣的视频，视频内容就是人们站在大街上和别人攀谈（被别人叫住问路），然后他们完全没有注意到，谈一半的时候，问路人被调包了！
There are some quite humorous videos of people who start talking to someone on the street (who has stopped them and asked for directions) and then don't notice when the person actually changes!
1981年，43%的人们都说自己在过去一年中同警察有过接触，主要是在街道上问路；而到了2006年，这一比率下滑至27%，大部分还是因为犯罪。
In 1981 43% of people reported having contacted the police in the past year, usually just to ask directions in the street. By 2006 that had fallen to 27%, of whom most had reported a crime.
1981年，43%的人们都说自己在过去一年中同警察有过接触，主要是在街道上问路；而到了2006年，这一比率下滑至27%，大部分还是因为犯罪。
In 1981 43% of people reported having contacted the police in the past year, usually just to ask directions in the street. By 2006 that had fallen to 27%, of whom most had reported a crime.
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