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Oracle中檢查是否需要重構(gòu)索引的sql

 更新時間：2013年08月08日 16:49:11   作者：  
經(jīng)常需要在Oracle中檢查是否需要重構(gòu)索引，在此寫了個示例語句，有此需求的朋友可以參考下，希望對大家有所幫助
復(fù)制代碼 代碼如下:

SELECT
height, /*Height of the B-Tree*/
blocks, /* Blocks in the index segment */
name, /*index name */
lf_rows, /* number of leaf rows in the index */
lf_blks, /* number of leaf blocks in the index */
del_lf_rows, /* number of deleted leaf rows in the index */
rows_per_key /* average number of rows per distinct key */
blk_gets_per_access /* consistent mode block reads (gets) */
FROM INDEX_STATS
WHERE NAME='INDEX_NAME';

復(fù)制代碼 代碼如下:

ANALYZE index INDEX_NAME VALIDATE STRUCTURE


HEIGHT:
This column refers to the height of the B-tree index, and it's usually at the 1, 2, or 3 level.
If large inserts push the index height beyond a level of 4, it's time to rebuild, which flattens the B-tree.

DEL_LF_ROWS:
This is the number of leaf nodes deleted due to the deletion of rows.
Oracle doesn't rebuild indexes automatically and, consequently, too many deleted leaf rows can lead to an unbalanced B-tree.

BLK_GETS_PER_ACCESS:
You can look at the BLK_GETS_PER_ACCESS column to see how much logical I/O it takes to retrieve data from the index. If this row shows a double-digit number, you should probably start rebuilding the index.

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