CREATE OR REPLACE FUNCTION pg_catalog.citus_prepare_pg_upgrade()
    RETURNS void
    LANGUAGE plpgsql
    SET search_path = pg_catalog
    AS $cppu$
BEGIN
    --
    -- Drop existing backup tables
    --
    DROP TABLE IF EXISTS public.pg_dist_partition;
    DROP TABLE IF EXISTS public.pg_dist_shard;
    DROP TABLE IF EXISTS public.pg_dist_placement;
    DROP TABLE IF EXISTS public.pg_dist_node_metadata;
    DROP TABLE IF EXISTS public.pg_dist_node;
    DROP TABLE IF EXISTS public.pg_dist_local_group;
    DROP TABLE IF EXISTS public.pg_dist_transaction;
    DROP TABLE IF EXISTS public.pg_dist_colocation;
    DROP TABLE IF EXISTS public.pg_dist_authinfo;
    DROP TABLE IF EXISTS public.pg_dist_poolinfo;
    DROP TABLE IF EXISTS public.pg_dist_rebalance_strategy;

    --
    -- backup citus catalog tables
    --
    CREATE TABLE public.pg_dist_partition AS SELECT * FROM pg_catalog.pg_dist_partition;
    CREATE TABLE public.pg_dist_shard AS SELECT * FROM pg_catalog.pg_dist_shard;
    CREATE TABLE public.pg_dist_placement AS SELECT * FROM pg_catalog.pg_dist_placement;
    CREATE TABLE public.pg_dist_node_metadata AS SELECT * FROM pg_catalog.pg_dist_node_metadata;
    CREATE TABLE public.pg_dist_node AS SELECT * FROM pg_catalog.pg_dist_node;
    CREATE TABLE public.pg_dist_local_group AS SELECT * FROM pg_catalog.pg_dist_local_group;
    CREATE TABLE public.pg_dist_transaction AS SELECT * FROM pg_catalog.pg_dist_transaction;
    CREATE TABLE public.pg_dist_colocation AS SELECT * FROM pg_catalog.pg_dist_colocation;
    -- enterprise catalog tables
    CREATE TABLE public.pg_dist_authinfo AS SELECT * FROM pg_catalog.pg_dist_authinfo;
    CREATE TABLE public.pg_dist_poolinfo AS SELECT * FROM pg_catalog.pg_dist_poolinfo;
    CREATE TABLE public.pg_dist_rebalance_strategy AS SELECT
        name,
        default_strategy,
        shard_cost_function::regprocedure::text,
        node_capacity_function::regprocedure::text,
        shard_allowed_on_node_function::regprocedure::text,
        default_threshold,
        minimum_threshold
    FROM pg_catalog.pg_dist_rebalance_strategy;

    -- store upgrade stable identifiers on pg_dist_object catalog
    UPDATE citus.pg_dist_object
       SET (type, object_names, object_args) = (SELECT * FROM pg_identify_object_as_address(classid, objid, objsubid));
END;
$cppu$;

COMMENT ON FUNCTION pg_catalog.citus_prepare_pg_upgrade()
    IS 'perform tasks to copy citus settings to a location that could later be restored after pg_upgrade is done';
