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
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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?
