lemmy/migrations/2020-09-07-231141_add_migration_utils/up.sql

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create schema utils;
create table utils.deps_saved_ddl
(
id serial NOT NULL,
view_schema character varying(255),
view_name character varying(255),
ddl_to_run text,
CONSTRAINT deps_saved_ddl_pkey PRIMARY KEY (id)
);
create or replace function utils.save_and_drop_views(p_view_schema name, p_view_name name)
RETURNS void
LANGUAGE plpgsql
COST 100
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::name, 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
if v_curr.obj_type = 'v' then
insert into utils.deps_saved_ddl(view_schema, view_name, 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;
execute 'DROP VIEW' || ' ' || v_curr.obj_schema || '.' || v_curr.obj_name;
end if;
end loop;
end;
$BODY$;
create or replace function utils.restore_views(p_view_schema character varying, p_view_name character varying)
RETURNS void
LANGUAGE plpgsql
COST 100
AS $BODY$
declare
v_curr record;
begin
for v_curr in
(
select ddl_to_run, id
from utils.deps_saved_ddl
where view_schema = p_view_schema and view_name = p_view_name
order by id desc
) loop
begin
execute v_curr.ddl_to_run;
delete from utils.deps_saved_ddl where id = v_curr.id;
EXCEPTION WHEN OTHERS THEN
-- keep looping, but please check for errors or remove left overs to handle manually
end;
end loop;
end;
$BODY$;