更改其他视图中使用的列的类型 [英] Changing the type of a column used in other views

问题描述

create table base (name character varying(255));                                                                                                                                                        
create view v1 as select *, now() from base;                                                        
create view v2 as select * from v1 where name = 'joe';
alter table base alter column name type text;                                                       

给出此错误：

cannot alter type of a column used by a view or rule
DETAIL:  rule _RETURN on view v1 depends on column "name"

这有点烦人，因为现在我必须重新创建所有引用 base.name 列的视图。 。当我有引用其他视图的视图时，这尤其烦人。

This is sort of annoying, because now I have to recreate all the views that reference the base.name column. It's especially annoying when I have views that reference other views.

我希望能够执行的操作如下：

What I'd love to be able to do is something like:

select recreate_views('v1', 'v2', 'alter table base alter column name type text');

并让该函数获取v1和v2的视图定义，将其删除，运行指定的代码，然后重新创建v1和v2。如果我可以使用Ruby，则可能会让函数采用一个function / block / lambda，例如

And have the function get the view definitions for v1 and v2, drop them, run the code specified, then recreate v1 and v2. If I could use Ruby, I'd probably have the function take a function/block/lambda, like

recreate_views 'v1', 'v2' do
  alter table base alter column name type text
end

这样可能吗？

推荐答案

我认为这可以满足您的要求，尽管我将视图列表移至args的末尾与VARIADIC语义兼容。

I think this does what you want, though I moved the view list to the end of args to be compatible with VARIADIC semantics.

CREATE OR REPLACE FUNCTION recreate_views(run_me text, VARIADIC views text[])
  RETURNS void
AS  $$
DECLARE
  view_defs text[];
  i integer;
  def text;
BEGIN
  for i in array_lower(views,1) .. array_upper(views,1) loop
    select definition into def from pg_views where viewname = views[i];
    view_defs[i] := def;
    EXECUTE 'DROP VIEW ' || views[i];
  end loop;

  EXECUTE run_me;

  for i in reverse array_upper(views,1) .. array_lower(views,1) loop
    def = 'CREATE OR REPLACE VIEW ' || quote_ident( views[i] ) || ' AS ' || view_defs[i];
    EXECUTE def;
  end loop;

END
$$
LANGUAGE plpgsql;

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