Downgrade from 9.4 to 9.3 to 9.2

citus--9.2-4--9.2-2.sql

-- citus--9.2-4--9.2-2
-- this is an empty downgrade path since citus--9.2-2--9.2-4.sql is empty

citus--9.3-2--9.2-4.sql

-- citus--9.3-2--9.2-4
-- this is a downgrade path that will revert the changes made in citus--9.2-4--9.3-2.sql
--
-- 9.3-2 added citus extension owner as a distributed object, if not already in there.
-- However we can not really know if it was a distributed owner prior to 9.3-2.
-- That's why we leave the record in place.

-- Revert the return type to void
DROP FUNCTION pg_catalog.citus_extradata_container(INTERNAL);
CREATE FUNCTION pg_catalog.citus_extradata_container(INTERNAL)
    RETURNS void
    LANGUAGE C
    AS 'MODULE_PATHNAME', $$citus_extradata_container$$;
COMMENT ON FUNCTION pg_catalog.citus_extradata_container(INTERNAL)
    IS 'placeholder function to store additional data in postgres node trees';

-- Remove newly introduced functions that are absent in earlier versions
DROP FUNCTION pg_catalog.update_distributed_table_colocation(regclass, text);
DROP FUNCTION pg_catalog.replicate_reference_tables();
DROP FUNCTION pg_catalog.citus_remote_connection_stats(
    OUT hostname text,
    OUT port int,
    OUT database_name text,
    OUT connection_count_to_node int);
DROP FUNCTION pg_catalog.worker_create_or_alter_role(
    role_name text,
    create_role_utility_query text,
    alter_role_utility_query text);
DROP FUNCTION pg_catalog.truncate_local_data_after_distributing_table(
    function_name regclass);

citus--9.4-1--9.3-2.sql

-- citus--9.4-1--9.3-2
-- this is a downgrade path that will revert the changes made in citus--9.3-2--9.4-1.sql

DROP FUNCTION pg_catalog.worker_last_saved_explain_analyze();
DROP FUNCTION pg_catalog.worker_save_query_explain_analyze(query text,
                                                           options jsonb);

Instructions.md

Instructions to downgrade from v9.4.0 to 9.3.x:

1. Install Citus v9.3.x
2. Copy citus--9.4-1--9.3-2.sql to /share/extension/citus--9.4-1--9.3-2.sql
3. Restart PostgreSQL
4. Run: ALTER EXTENSION citus UPDATE;
5. Delete /share/extension/citus--9.4-1--9.3-2.sql

Instructions to downgrade from v9.4.0 to 9.2.4:

1. Install Citus v9.2.4
2. Copy citus--9.4-1--9.3-2.sql and citus--9.3-2--9.2-4.sql to /share/extension/
3. Restart PostgreSQL
4. Run: ALTER EXTENSION citus UPDATE;
5. Delete /share/extension/citus--9.4-1--9.3-2.sql and citus--9.3-2--9.2-4.sql

Instructions to downgrade from v9.4.0 to 9.2.0/9.2.1/9.2.2:

1. Install Citus v9.2.x
2. Copy citus--9.4-1--9.3-2.sql, citus--9.3-2--9.2-4.sql and citus--9.2-4--9.2-2.sql to /share/extension/
3. Restart PostgreSQL
4. Run: ALTER EXTENSION citus UPDATE;
5. Delete /share/extension/citus--9.4-1--9.3-2.sql, citus--9.3-2--9.2-4.sql and citus--9.2-4--9.2-2.sql

---

Notes:

• If you build from source and you wish to skip manual script installation steps, you can remove cleanup-before-install make target dependency here: https://github.com/citusdata/citus/blob/d1bab78d7975936a3d7276cc4c422532744868ad/src/backend/distributed/Makefile#L77 If you remove this line before make install commands, you can safely skip steps 2 and 5.
• To see how Citus versions are coupled with schema migration versions see the diagram here