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;
$BODY$;