关键字
索引失效，禁用索引，启用索引，索引重建、人大金仓、
问题描述
Oracle能够通过语句设置，使索引失效，支持设置索引的启用禁用操作
create table t1(c1 int,c2 varchar(10));
create index idx_t1 on t1(c1);
--禁用索引，设置索引失效
alter index idx_t1 unusable;
--启用索引，重建索引
alter index idx_t1 rebuild;
问题分析
KES不具备设置索引启用，禁用的能力。
解决方案
create index语句添加usable、unusable支持创建索引时指定索引状态，未指定时默认为启用状态。
新增语法：
CREATE [ UNIQUE ] INDEX [ CONCURRENTLY ] [ [ IF NOT EXISTS ] name ]
ON [ ONLY ] table_name [ USING method ]
( { column_name | ( expression ) } [ COLLATE collation ]
opclass \] \[ ASC \| DESC \] \[ NULLS { FIRST \| LAST } \] \[, ...\] ) \[ INCLUDE ( column_name \[, ...\] )
WITH ( storage_parameter = value \[, ... \] )
TABLESPACE tablespace_name
UNUSABLE \| USABLE
WHERE predicate
描述：
unusable 创建一个不可用状态的索引
usable 创建一个可用状态的索引，默认状态
ALTER INDEX name UNUSABLE
ALTER INDEX name REBUILD
--create index使用
create table tab_btree (id int,name text);
insert into tab_btree values(generate_series(1,100000),md5(random()::text));
create index i_btree on tab_btree using btree(id);
analyze;
explain (costs off) select * from tab_btree where id < 10;
-- alter index name unusable
alter index i_btree unusable;
explain (costs off) select * from tab_btree where id < 10;
-- alter index name rebuild
alter index i_btree rebuild;
explain (costs off) select * from tab_btree where id < 10;