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PostgreSQL: How to handle table and view dependencies
create table deps_saved_ddl
(
deps_id serial primary key,
deps_view_schema varchar(255),
deps_view_name varchar(255),
deps_ddl_to_run text
);
create or replace function deps_save_and_drop_dependencies(p_view_schema varchar, p_view_name varchar) returns void as
$$
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 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 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 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 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 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;
$$
LANGUAGE plpgsql;
create or replace function deps_restore_dependencies(p_view_schema varchar, p_view_name varchar) returns void as
$$
declare
v_curr record;
begin
for v_curr in
(
select deps_ddl_to_run
from deps_saved_ddl
where deps_view_schema = p_view_schema and deps_view_name = p_view_name
order by deps_id desc
) loop
execute v_curr.deps_ddl_to_run;
end loop;
delete from deps_saved_ddl
where deps_view_schema = p_view_schema and deps_view_name = p_view_name;
end;
$$
LANGUAGE plpgsql;

claudep commented Mar 30, 2015

Awesome script. I've added name quoting (I have views names with spaces) in https://gist.github.com/claudep/b3c2e348eab19896fa1c/revisions

mingDRG commented Apr 11, 2015

does this function restore MV and indexes? I have a MV base on selecting from another MV. Thx.

diogob commented Oct 13, 2015

Beautiful! Saved me a lot of time ❤️

maerco commented May 25, 2016

this is not performing backup of rules

fosils commented Jun 3, 2016

@maerco Thank you for your comment. Do you know how it behaves if there are rules involved. Will they just get dropped or will it fail with an error message?

fosils commented Jun 3, 2016

This script seems to work so far. Brilliant. It solved this problem for me:
https://forums.aws.amazon.com/thread.jspa?threadID=225781&tstart=0

These were the commands I ran to add a label to an enum on Amazon RDS.

CREATE TYPE "public"."enum_new" AS ENUM ('value1', 'value2');
select deps_save_and_drop_dependencies('public', 'customers');
alter table customers alter column some_column type enum_new using enum_type::text::enum_new;
select deps_restore_dependencies('public', 'customers');

fosils commented Aug 14, 2016

I would pay $80 if anyone would add the ability to also store rules on any of the dropped tables/views or is it already like that?

amazing work , thanks alot.

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