When Rebuild INDEX?

本文介绍如何利用Analyze Index命令验证Oracle数据库中的索引结构完整性,包括检查逻辑坏块,并通过示例展示了如何查看索引的高度、叶子节点数量及已删除的叶子节点数,这些信息有助于决定是否需要重建索引。

大家都知道analyze来分析统计信息,但是很少用来分析表或者索引是否有坏块。(主要是指逻辑坏块,不是介质坏块)。

其实analyze index?xx validate structure;对于DBA来说,还有另外的作用,就是何时该REBUILD INDEX;

范例如下:

@>analyze index ZEUS_CUSTOMER_AI1_OI_IND validate structure;

Index analyzed.

@>select name,height,lf_rows,del_lf_rows from index_stats;

NAME?????????????????????????????? HEIGHT??? LF_ROWS DEL_LF_ROWS
—————————— ———- ———- ———–
ZEUS_CUSTOMER_AI1_OI_IND??????????????? 3???? 941235???????? 691

@>

lf_rows表示这个INDEX有多少的叶子节点;

del_lf_rows表示有多少个叶子节点被删除了。

PS:说实话,在我管的几个系统里,物理删除真的很少,很少。

set serverout on; declare v_sql varchar2(300); v_Errmsg varchar2(300); begin delete from user_index_stats; commit; for i in (select table_name, index_name, num_rows from user_indexes where index_type like '%NORMAL%' and partitioned='NO' and not (regexp_like(table_name,'^TMP[[:alnum:]]{27}$')) and temporary='N' and num_rows > 0 order by 3 desc) loop begin v_sql := 'analyze index '||i.index_name||' validate structure '; execute immediate v_sql; insert into user_index_stats(table_name, height, blocks, index_name, partition_name, lf_rows, lf_blks, lf_rows_len, lf_blk_len, br_rows, br_blks, br_rows_len, br_blk_len, del_lf_rows, del_lf_rows_len, distinct_keys, most_repeated_key, btree_space, used_space, pct_used, rows_per_key, blks_gets_per_access, pre_rows, pre_rows_len, opt_cmpr_count, opt_cmpr_pctsave) select i.table_name, height, blocks, name, partition_name, lf_rows, lf_blks, lf_rows_len, lf_blk_len, br_rows, br_blks, br_rows_len, br_blk_len, del_lf_rows, del_lf_rows_len, distinct_keys, most_repeated_key, btree_space, used_space, pct_used, rows_per_key, blks_gets_per_access, pre_rows, pre_rows_len, opt_cmpr_count, opt_cmpr_pctsave from index_stats; exception when others then v_Errmsg :=substr(dbms_utility.format_error_backtrace,1,150); v_Errmsg :=v_Errmsg||substr(dbms_utility.format_error_stack,1,150); insert into user_index_stats(table_name, index_name, comments) values (i.table_name, i.index_name, v_Errmsg); end; end loop; commit; for i in (select table_name, index_name, round(del_lf_rows/lf_rows,2) del_pct, blocks, lf_rows, lf_rows_len, del_lf_rows, del_lf_rows_len, (lf_rows - del_lf_rows) gap_num_rows from user_index_stats where height >= 3 and (lf_rows > 0 and del_lf_rows/lf_rows >= 0.2) order by height desc, del_lf_rows/lf_rows desc) loop begin v_sql := 'alter index '||i.index_name||' rebuild online parallel 4'; execute immediate v_sql; v_sql := 'alter index '||i.index_name||' noparallel'; execute immediate v_sql; --dbms_output.put_line(i.index_name); update user_index_stats set rebuild_date = sysdate where index_name = i.index_name; commit; exception when others then v_Errmsg :=substr(dbms_utility.format_error_backtrace,1,150); v_Errmsg :=v_Errmsg||substr(dbms_utility.format_error_stack,1,150); update user_index_stats set comments = v_Errmsg where index_name = i.index_name; end; commit; end loop; end;
08-27
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