index_stats视图各列的含义
index_stats视图各列的含义
<div class="postbody">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。
INDEX_STATS
statistics on the b-tree
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
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