如何对系统默认的约束名和索引名重命名

as
--查找用户所有表的游标
cursor cur_table is select table_name from user_tables;

--查找某张表所有约束的游标
cursor cur_cons (c_table varchar2) is select c.constraint_name,c.constraint_type,
c.search_condition from user_constraints c where c.table_name=c_table
and substr(c.constraint_name,2,2) <> 'K_';

--查找某个约束所有字段的游标
cursor cur_columns(c_cons varchar2) is select column_name from user_cons_columns
where constraint_name=c_cons;

--存储修改后的约束名
v_new_cons_name varchar2(100);

--存储修改约束名的SQL语句
v_sql varchar2(150);

--存储重名的个数
cnt number :=1;

--存储新索引名的个数
n_idx number;

--存储新约束名的个数
n_con number;

begin
--循环取表名
for cur_ltable in cur_table loop

--循环取约束名
for cur_lcons in cur_cons(cur_ltable.table_name) loop

v_new_cons_name :=null;

--循环取字段名
for cur_lcolumns in cur_columns(cur_lcons.constraint_name) loop
v_new_cons_name := v_new_cons_name || cur_lcolumns.column_name;
end loop;
v_new_cons_name := replace(v_new_cons_name,'_','');
v_new_cons_name := cur_ltable.table_name ||'_' || v_new_cons_name;

if cur_lcons.constraint_type='P' then
v_new_cons_name := 'PK_' || v_new_cons_name;
elsif cur_lcons.constraint_type='R' then
v_new_cons_name := 'FK_' || v_new_cons_name;
elsif cur_lcons.constraint_type='U' then
v_new_cons_name := 'UK_' || v_new_cons_name;
elsif cur_lcons.constraint_type='C'
and instr(cur_lcons.search_condition,'IS NOT NULL') > 0 then
v_new_cons_name := 'CK_' || v_new_cons_name || 'NOTNULL' ;
elsif cur_lcons.constraint_type='C'
and instr(cur_lcons.search_condition,'IS NOT NULL') = 0
and cur_lcons.search_condition is not null then
v_new_cons_name := 'CK_' || v_new_cons_name;
end if;

--约束名如果超过30个字符的处理
if length(v_new_cons_name) > 29 then
v_new_cons_name := substr(v_new_cons_name,1,15) || substr(v_new_cons_name,-14);
end if;

--查找系统里是否有新的约束名
select count(*) into n_con from user_constraints where constraint_name=v_new_cons_name;
select count(*) into n_idx from user_indexes where index_name=v_new_cons_name;
if n_con > 0 or n_idx > 0 then
v_new_cons_name := v_new_cons_name || to_char(cnt);
cnt := cnt +1;
end if;

--对由主键和唯一键创建的索引进行改名,改后的名