1 查询表约束信息

SELECT
tc.constraint_name, tc.table_name, kcu.column_name,
ccu.table_name AS foreign_table_name,
ccu.column_name AS foreign_column_name,
tc.is_deferrable,tc.initially_deferred
FROM
information_schema.table_constraints AS tc
JOIN information_schema.key_column_usage AS kcu ON tc.constraint_name = kcu.constraint_name
JOIN information_schema.constraint_column_usage AS ccu ON ccu.constraint_name = tc.constraint_name
WHERE tc.table_name = 'xxxxx';

2 查询表的索引信息

select from pg_indexes where tablename='xxxx';
select from pg_statio_all_indexes where relname='xxxx';

3 修改表的字段类型

ALTER TABLE tabname ALTER colname TYPE varchar(100)