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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
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
mingDRG commented Apr 11, 2015

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

@diogob
diogob commented Oct 13, 2015

Beautiful! Saved me a lot of time ❤️

@maerco
maerco commented May 25, 2016

this is not performing backup of rules

@fosils
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
fosils commented Jun 3, 2016 edited

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
fosils commented Aug 14, 2016 edited

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?

@shripatel

amazing work , thanks alot.

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