今天开发需要删除AWS Redshift的一个归档表，但是直接drop发生了如下报错，发现有其他对象依赖这个表，导致无法直接删除，但是报错没有直接显示是什么对象依赖它，可能是有视图，外键等约束
analyticsprod=# DROP TABLE IF EXISTS facts.auto_events_bk_20170223;
ERROR: cannot drop table auto_events_bk_20170223 because other objects depend on it
HINT: Use DROP ... CASCADE to drop the dependent objects too.
通过\d+ auto_events_bk_20170223 查看表结构，发现并没有其他表的外键约束，所以排除；
然后通过\dv+命令在schema：facts下查看视图，但是发现没有任何view存在，但是view可能存在其他schema或db,
那么问题来了,如何在整个数据库中找到与这个表有依赖的的view?
这里AWS Redshift已经给我们提供了一个好的方法,参考链接：https://docs.aws.amazon.com/redshift/latest/dg/r_DROP_TABLE.html
创建一个视图find_depend:
create view find_depend as select distinct c_p.oid as tbloid, n_p.nspname as schemaname, c_p.relname as name, n_c.nspname as refbyschemaname, c_c.relname as refbyname, c_c.oid as viewoid from pg_catalog.pg_class c_p join pg_catalog.pg_depend d_p on c_p.relfilenode = d_p.refobjid join pg_catalog.pg_depend d_c on d_p.objid = d_c.objid join pg_catalog.pg_class c_c on d_c.refobjid = c_c.relfilenode left outer join pg_namespace n_p on c_p.relnamespace = n_p.oid left outer join pg_namespace n_c on c_c.relnamespace = n_c.oid where d_c.deptype = 'i'::"char" and c_c.relkind = 'v'::"char";
查询视图找到与表auto_events_bk_20170223相关的view:
analyticsprod=# select * from facts.find_depend where schemaname='facts' and name not in ('find_depend') order by name;
tbloid | schemaname | name | refbyschemaname | refbyname | viewoid
--------+------------+-------------------------+-----------------+-------------+---------
879566 | facts | auto_events_bk_20170223 | public | map_routes2 | 965969
879566 | facts | auto_events_bk_20170223 | public | map_routes | 966155
879566 | facts | auto_events_bk_20170223 | public | map_edges | 1019697
(3 rows)
analyticsprod=# set search_path to public;
analyticsprod=# \dv
List of relations
schema | name | type | owner
--------+-----------------------+------+-------
public | map_edges | view | fengw
public | map_edges_group | view | fengw
public | map_route_edges_group | view | fengw
public | map_routes | view | fengw
public | map_routes2 | view | fengw
public | map_routes_group | view | fengw
(6 rows)
最后如果判断这些相关的view没有用的话，可以通过命令drop table auto_events_bk_20170223 cascade删除表，包括视图一同删除。
