python - psycopg2 psycopg2.InternalError 依赖对象

Question

我在 heroku 上使用 peewee，但根据 peewee 文档，删除相关表必须在代码中完成。

问题是如何？

我有以下型号

class WebPage(Model):
  title = CharField()

class Term(Model):
  name = CharField()

class WebPageTerms(Model):
  term = ForeignKeyField(Term)
  webpage = ForeignKeyField(WebPage)

包含postgresql自定义语句的drop table方法:

def drop_tables():
   WebPage.drop_table(fail_silently=True)
   Term.drop_table(fail_silently=True)
   WebPageTerms.drop_table(fail_silently=True)

作为部署的一部分，我删除所有表并创建它们以添加新字段。

我试过以下方法，但还是不行:

conn = psycopg2.connect("dbname='' user='' host='' password=''")
curr = conn.cursor()
curr.execute("DROP table webpageterms CASCADE")
curr.execute("DROP table webpage CASCADE")
curr.close()
conn.close()

但我总是得到同样的错误

psycopg2.InternalError: cannot drop table webpage because other objects depend on it DETAIL: constraint webpageterms_webpage_id_fkey on table webpageterms depends on table webpage HINT: Use DROP ... CASCADE to drop the dependent objects too.

我怎样才能删除这些表？

** 编辑 **试图将代码更改为:

curr.execute("ALTER TABLE webpageterms DROP CONSTRAINT webpageterms_webpage_id_fkey")

但我得到:

psycopg2.InternalError: cannot drop table webpage because other objects depend on it
DETAIL:  constraint webpageterms_webpage_id_fkey on table webpageterms depends on table webpage
HINT:  Use DROP ... CASCADE to drop the dependent objects too.

Answer 1

按以下顺序放置它们:

WebPageTerms.drop_table(fail_silently=True)
Term.drop_table(fail_silently=True)
WebPage.drop_table(fail_silently=True)

Peewee 带有一个删除表的帮助程序——它通过遵循外键为您按拓扑对它们进行排序:

from peewee import drop_model_tables
drop_model_tables([WebPage, Term, WebPageTerms])  # <-- will sort them correctly