index_stats视图各列的含义

index_stats视图来收集B树索引的统计信息。可以从中查到该用户拥有索引的名字，高度等等详细信息，以下是其具体的列名及其含义

 

Columns  

     ___________________________  

     

     OPT_CMPR_PCTSAVE  

        percentage storage saving expected from optimal prefix compression 

      百分比：保存压缩头 

     HEIGHT  

        height of the b-tree 

      b-tree的高度 

     BLOCKS  

        blocks allocated to the segment 

      这个索引段，分配的块数量 

     NAME  

        name of the index 

      索引的名字 

     PARTITION_NAME  

        name of the index partition,if partitioned 

      如果分区了，分区的名字 

     LF_ROWS  

        number of leaf rows (values in the index) 

      叶子节点的行数 

     LF_BLKS  

        number of leaf blocks in the b-tree

      叶子块的数量  

     LF_ROWS_LEN  

        sum of the lengths of all the leaf rows 

      叶子行的总长度 （？） 

     LF_BLK_LEN  

        useable space in a leaf block 

      叶子块的可用空间 

     BR_ROWS  

        number of branch rows 

      分支行的数量 

     BR_BLKS  

        number of branch blocks in the b-tree 

      分支块的数量 

     BR_ROWS_LEN  

        sum of the lengths of all the branch blocks in the b-tree 

      所有分支块的总长度 

     BR_BLK_LEN  

        useable space in a branch block 

      分支块可用空间 

     DEL_LF_ROWS  

        number of deleted leaf rows in the index 

      被删除的叶子行数量 

     DEL_LF_ROWS_LEN  

        total length of all deleted rows in the index 

      所有被删除行的总长度 

     DISTINCT_KEYS  

        number of distinct keys in the index 

      不同键值的数量 

     MOST_REPEATED_KEY  

        how many times the most repeated key is repeated 

      最大重复键的重复次数 

     BTREE_SPACE  

        total space currently allocated in the b-tree 

      当前分配的总空间 

     USED_SPACE  

        total space that is currently being used in the b-tree 

      当前使用的总空间 

     PCT_USED  

        percent of space allocated in the b-tree that is being used 

      使用的空间百分比 

     ROWS_PER_KEY  

        average number of rows per distinct key 

      每个键值平均行数 

     BLKS_GETS_PER_ACCESS  

        Expected number of consistent mode block gets per row. 

      This assumes that a row chosen at random from the table is being searched for using the index     

     PRE_ROWS  

        number of prefix rows (values in the index)  

     PRE_ROWS_LEN  

        sum of lengths of all prefix rows  

     OPT_CMPR_COUNT  

        optimal prefix compression count for the index