postgres alter表有问题

我遇到了这个问题,找不到解决办法。不幸的是,据我所知,必须删除视图,更改基础表上的列类型,然后重新创建视图。这完全可以在单个事务中发生。

约束延迟不适用于这个问题。换句话说,甚至 SET CONSTRAINTS ALL DEFERRED 对这一限制没有影响。具体来说,约束延迟不适用于打印的一致性检查 ERROR: cannot alter type of a column used by a view or rule 当试图改变视图下列的类型时。

如果你不需要改变 类型 在这个领域,但仅仅是它的规模,这种方法应该是有效的:

从这些表开始:

CREATE TABLE foo (id integer primary key, names varchar(10));
CREATE VIEW voo AS (SELECT id, names FROM foo);

\d foo 和 \d voo 两者的长度都显示为10:

id     | integer               | not null
names  | character varying(10) | 

现在将长度改为20 pg_attribute 表:

UPDATE pg_attribute SET atttypmod = 20+4
WHERE attrelid IN ('foo'::regclass, 'voo'::regclass)
AND attname = 'names';

(注:20+4是一些疯狂的PostgreSQL遗留物,+4是强制的。)

现在 D.FO 显示:

id integer不为空
名称字符变化(10)|

奖金:这比做得快:

ALTER TABLE foo ALTER COLUMN names TYPE varchar(20);

从技术上讲,您可以在不更改视图列大小的情况下更改表列的大小,但不能保证会产生什么副作用;最好同时更改这两个列。

来源和更全面的解释: http://sniptools.com/databases/resize-a-column-in-a-postgresql-table-without-changing-data

我参加晚会有点晚了,但在这个问题发表几年后,通过下面引用的一篇文章(不是我的——我只是感谢他的才华的受益者)发布了一个出色的解决方案。

我刚刚在一个在136个独立视图中被引用(第一级)的对象上测试了这一点,并且这些视图中的每一个都在其他视图中被引用。解决方案只需几秒钟。

因此,请阅读本文并复制粘贴表和列出的两个函数:

http://mwenus.blogspot.com/2014/04/postgresql-how-to-handle-table-and-view.html

实施示例:

alter table mdm.global_item_master_swap
alter column prod_id type varchar(128),
alter column prod_nme type varchar(512);

错误:无法更改视图或规则详细信息使用的列的类型: 规则“视图返回工具箱”报告。“平均设置成本”取决于 “产品ID”列 **********错误**********

错误:无法更改视图或规则使用的列的类型

现在,对于PostgreSQL忍者魔咒:

select util.deps_save_and_drop_dependencies('mdm', 'global_item_master_swap');


alter table mdm.global_item_master_swap
alter column prod_id type varchar(128),
alter column prod_nme type varchar(512);


select util.deps_restore_dependencies('mdm', 'global_item_master_swap');

--编辑:2018年11月13日--

上面的链接可能已经死了。这是两个过程的代码:

存储DDL的表:

CREATE TABLE util.deps_saved_ddl
(
  deps_id serial NOT NULL,
  deps_view_schema character varying(255),
  deps_view_name character varying(255),
  deps_ddl_to_run text,
  CONSTRAINT deps_saved_ddl_pkey PRIMARY KEY (deps_id)
);

保存和删除:

CREATE OR REPLACE FUNCTION util.deps_save_and_drop_dependencies(
    p_view_schema character varying,
    p_view_name character varying)
  RETURNS void AS
$BODY$
declare
  v_curr record;
begin
for v_curr in 
(
  select obj_schema, obj_name, obj_type from
  (
  with recursive recursive_deps(obj_schema, obj_name, obj_type, depth) as 
  (
    select p_view_schema, p_view_name, null::varchar, 0
    union
    select dep_schema::varchar, dep_name::varchar, dep_type::varchar, recursive_deps.depth + 1 from 
    (
      select ref_nsp.nspname ref_schema, ref_cl.relname ref_name, 
      rwr_cl.relkind dep_type,
      rwr_nsp.nspname dep_schema,
      rwr_cl.relname dep_name
      from pg_depend dep
      join pg_class ref_cl on dep.refobjid = ref_cl.oid
      join pg_namespace ref_nsp on ref_cl.relnamespace = ref_nsp.oid
      join pg_rewrite rwr on dep.objid = rwr.oid
      join pg_class rwr_cl on rwr.ev_class = rwr_cl.oid
      join pg_namespace rwr_nsp on rwr_cl.relnamespace = rwr_nsp.oid
      where dep.deptype = 'n'
      and dep.classid = 'pg_rewrite'::regclass
    ) deps
    join recursive_deps on deps.ref_schema = recursive_deps.obj_schema and deps.ref_name = recursive_deps.obj_name
    where (deps.ref_schema != deps.dep_schema or deps.ref_name != deps.dep_name)
  )
  select obj_schema, obj_name, obj_type, depth
  from recursive_deps 
  where depth > 0
  ) t
  group by obj_schema, obj_name, obj_type
  order by max(depth) desc
) loop

  insert into util.deps_saved_ddl(deps_view_schema, deps_view_name, deps_ddl_to_run)
  select p_view_schema, p_view_name, 'COMMENT ON ' ||
  case
  when c.relkind = 'v' then 'VIEW'
  when c.relkind = 'm' then 'MATERIALIZED VIEW'
  else ''
  end
  || ' ' || n.nspname || '.' || c.relname || ' IS ''' || replace(d.description, '''', '''''') || ''';'
  from pg_class c
  join pg_namespace n on n.oid = c.relnamespace
  join pg_description d on d.objoid = c.oid and d.objsubid = 0
  where n.nspname = v_curr.obj_schema and c.relname = v_curr.obj_name and d.description is not null;

  insert into util.deps_saved_ddl(deps_view_schema, deps_view_name, deps_ddl_to_run)
  select p_view_schema, p_view_name, 'COMMENT ON COLUMN ' || n.nspname || '.' || c.relname || '.' || a.attname || ' IS ''' || replace(d.description, '''', '''''') || ''';'
  from pg_class c
  join pg_attribute a on c.oid = a.attrelid
  join pg_namespace n on n.oid = c.relnamespace
  join pg_description d on d.objoid = c.oid and d.objsubid = a.attnum
  where n.nspname = v_curr.obj_schema and c.relname = v_curr.obj_name and d.description is not null;

  insert into util.deps_saved_ddl(deps_view_schema, deps_view_name, deps_ddl_to_run)
  select p_view_schema, p_view_name, 'GRANT ' || privilege_type || ' ON ' || table_schema || '.' || table_name || ' TO ' || grantee
  from information_schema.role_table_grants
  where table_schema = v_curr.obj_schema and table_name = v_curr.obj_name;

  if v_curr.obj_type = 'v' then
    insert into util.deps_saved_ddl(deps_view_schema, deps_view_name, deps_ddl_to_run)
    select p_view_schema, p_view_name, 'CREATE VIEW ' || v_curr.obj_schema || '.' || v_curr.obj_name || ' AS ' || view_definition
    from information_schema.views
    where table_schema = v_curr.obj_schema and table_name = v_curr.obj_name;
  elsif v_curr.obj_type = 'm' then
    insert into util.deps_saved_ddl(deps_view_schema, deps_view_name, deps_ddl_to_run)
    select p_view_schema, p_view_name, 'CREATE MATERIALIZED VIEW ' || v_curr.obj_schema || '.' || v_curr.obj_name || ' AS ' || definition
    from pg_matviews
    where schemaname = v_curr.obj_schema and matviewname = v_curr.obj_name;
  end if;

  execute 'DROP ' ||
  case 
    when v_curr.obj_type = 'v' then 'VIEW'
    when v_curr.obj_type = 'm' then 'MATERIALIZED VIEW'
  end
  || ' ' || v_curr.obj_schema || '.' || v_curr.obj_name;

end loop;
end;
$BODY$
  LANGUAGE plpgsql VOLATILE
  COST 100;

恢复:

CREATE OR REPLACE FUNCTION util.deps_restore_dependencies(
    p_view_schema character varying,
    p_view_name character varying)
  RETURNS void AS
$BODY$
declare
  v_curr record;
begin
for v_curr in 
(
  select deps_ddl_to_run 
  from util.deps_saved_ddl
  where deps_view_schema = p_view_schema and deps_view_name = p_view_name
  order by deps_id desc
) loop
  execute v_curr.deps_ddl_to_run;
end loop;
delete from util.deps_saved_ddl
where deps_view_schema = p_view_schema and deps_view_name = p_view_name;
end;
$BODY$
  LANGUAGE plpgsql VOLATILE
  COST 100;

我今天遇到了这个问题,找到了一个解决方法来避免删除和重新创建视图。我不能直接删除我的视图,因为它是一个主视图,在它上面有许多依赖的视图。除了有一个重建脚本来删除级联,然后重新创建我的所有视图之外,这是一个解决方案。

我将主视图更改为对有问题的列使用虚拟值,更改了表中的列,并将视图切换回该列。使用如下设置:

CREATE TABLE base_table
(
  base_table_id integer,
  base_table_field1 numeric(10,4)
);

CREATE OR REPLACE VIEW master_view AS 
  SELECT
    base_table_id AS id,
    (base_table_field1 * .01)::numeric AS field1
  FROM base_table;

CREATE OR REPLACE VIEW dependent_view AS 
  SELECT
    id AS dependent_id,
    field1 AS dependent_field1
  FROM master_view;

尝试如下更改基表字段1类型:

ALTER TABLE base_table ALTER COLUMN base_table_field1 TYPE numeric(10,6);

将出现此错误:

ERROR:  cannot alter type of a column used by a view or rule
DETAIL:  rule _RETURN on view master_view depends on column "base_table_field1"

如果将主视图更改为对该列使用虚拟值,如下所示:

CREATE OR REPLACE VIEW master_view AS 
  SELECT
    base_table_id AS id,
    0.9999 AS field1
  FROM base_table;

然后运行你的更改:

alter table base_table alter column base_table_field1 type numeric(10,6);

然后切换视图:

CREATE OR REPLACE VIEW master_view AS 
  SELECT
    base_table_id AS id,
    (base_table_field1 * .01)::numeric AS field1
  FROM base_table;

这完全取决于主视图的显式类型是否不变。因为我的视图使用'(base_table_field1*.01)::numeric as field1'它起作用,但是'base_table_field1 as field1'不会因为列类型改变。这种方法在我这样的情况下可能会有所帮助。