索引块

Each index block, which can lead to less I/O and better performance.

可以在索引块中存储跟过的索引键，减少I/O ，提高性能，节省空间

When an index block is read from a table into the key cache, it is placed at the end of the warm sublist.

当一个索引块被从表中读取到 Key Cache 中时，它被放在 warm 子链的尾部。

In an indexed file, the lowest level index block. It contains the relative block numbers and high keys of several data blocks.

索引文件中最低一级的索引块，其内容包括相对块号和几个数据块的高一级的关键字。

Compression is achieved by sharing the prefix entries among all the suffix entries in an index block.

这种共享使得每个索引块在提升性能的同时存储更多的键值，大量节省空间。

When operating an index block, it can not affect other index terms; hence it can online update the index information in any index block.

由于每一索引块只用于存储有关同一索引项的索引信息，所以在对一个索引块中进行操作时，不会影响其他索引项，于是可以对任何索引块中的索引信息进行在线更新。

If the clustering factor is roughly equal to BLOCKS minus FREE_BLOCKS from USER_TABLES then the chances are that a range scan will read one index block, and locate all of the data rows in needs in one or more adjacent blocks in the table.

若簇因子几乎与BLOCKS - FREE_BLOCKS（来自USER_TABLES）相近，一个区间扫描将可能读一个索引块，然后根据需要在一个或更多的临近块中定位所有数据行。

Prefix entries are available for sharing immediately after being written to the index block and remain available until the last deleted referencing suffix entry is cleaned out of the index block.

一个前缀被写入后立即就可以被此索引块内的后缀共享，直到所有引用此前缀的后缀都被删除为止。

Prefix entries are written to the index block only if the index block does not already contain a prefix entry whose value is equal to the present prefix entry.

应用键压缩后，生成索引时，如果一个键值的前缀在索引块中不存在，此前缀才会被写入索引块中。

If the application is multi-user then it means that every user will tend to write into the same index block and buffer busy waits will be the outcome as transactions 'queue' to write data to the hottest index block around.

若单用户执行应用程序，这不是什么问题。若应用是多用户的，则意味着每个用户将写入同一个索引块。

Contiguous allocation can suffer from external fragmentation.Direct access files cannot be supported with linked allocation.Indexed allocation may require substantial overhead for its index block.

邻接分配能承受外部碎片；直接访问文件不能为链接分配所支持；索引式分配又可能因其索引块而需要大量额外开销。

On the other hand, the more important thing is because the urban housing is a kind of heterogeneity products.

另一方面，更重要的是由于城市住房是一种异质性产品。

Climate histogram is the fall that collects place measure calm value, cent serves as cross axle for a few equal interval, the area that the frequency that the value appears according to place is accumulated and becomes will be determined inside each interval, discharge the graph that rise with post, also be called histogram.

气候直方图是将所收集的降水量测定值，分为几个相等的区间作为横轴，并将各区间内所测定值依所出现的次数累积而成的面积，用柱子排起来的图形，也叫做柱状图。