postgreSQL-如何查数据库表、字段以及字段类型、注释等信息？

--1.查询对象字段、注释和字段类型
select  t.schemaname
,c.relname object_name
,d.description object_comment
--,c.reltuples count
--,c.relkind object_type --r = 普通表，i = 索引，S = 序列，v = 视图， c = 复合类型，s = 特殊，t = TOAST表
--,c.relhaspkey primary_key --f：假，t-：真
,a.attname column_name
,db.description column_comment
,s.attrnums distributed_column
--,case when s.attrnums is not null then 'is distributed key' end distributed_column
--,a.attnum column_seq
,case p.typname
when 'int8' then 'bigint'
when 'int4' then 'integer'
when 'int2' then 'smallint'
when 'timestamp' then 'timestamp without time zone'
when 'date' then 'date'
when 'varchar' then 'character varying('||a.atttypmod - 4||')'
when 'numeric' then  'numeric('||(a.atttypmod - 4) / 65536||','||(atttypmod - 4) % 65536||')'
end column_type
,at.adsrc AS column_default
,CASE
WHEN a.attnotnull THEN
'not null'
ELSE
''
END AS column_not_null
--,p.typname
--,p.typlen
--,a.atttypmod - 4 as column_length
from pg_tables t
inner join pg_class c on t.tablename=c.relname
left join pg_description d on c.oid=d.objoid and d.objsubid=0
left join pg_description db on c.oid=db.objoid and db.objsubid>0
left join pg_attribute a on c.oid=a.attrelid and db.objsubid=a.attnum
left join ( select a.attrnums[i.i] attrnums,b.attname,a.localoid
from gp_distribution_policy a,
(select generate_series(1,10)) i(i),  --预计表分布键的个数为10个
pg_attribute b
where a.attrnums[i.i] is not null
and a.localoid=b.attrelid
and a.attrnums[i.i]=b.attnum ) s on c.oid=s.localoid and a.attnum=s.attrnums
left join pg_type p on a.atttypid=p.oid
left join pg_attrdef at on c.oid=at.adrelid and a.attnum=at.adnum
where upper(c.relname) = upper('bas_add_sub_rep') --表名
order by a.attnum;