转载自：http://blog.csdn.net/cicon/article/details/51577655
获取表名及注释：
select relname as tabname,cast(obj_description(relfilenode,'pg_class') as varchar) as comment from pg_class c
where relkind = 'r' and relname not like 'pg_%' and relname not like 'sql_%' order by relname
过滤掉分表：
加条件 and relchecks=0 即可
获取字段名、类型、注释、是否为空:
SELECT col_description(a.attrelid,a.attnum) as comment,format_type(a.atttypid,a.atttypmod) as type,a.attname as name, a.attnotnull as notnull
FROM pg_class as c,pg_attribute as a where c.relname = '表名' and a.attrelid = c.oid and a.attnum>0