Upgrading Citus

Upgrading Citus Versions

Citus adheres to semantic versioning with patch-, minor-, and major-versions. The upgrade process differs for each, requiring more effort for bigger version jumps.

Upgrading the Citus version requires first obtaining the new Citus extension and then installing it in each of your database instances. Citus uses separate packages for each minor version to ensure that running a default package upgrade will provide bug fixes but never break anything. Let’s start by examining patch upgrades, the easiest kind.

Patch Version Upgrade

To upgrade a Citus version to its latest patch, issue a standard upgrade command for your package manager. Assuming version 6.2 is currently installed:

Ubuntu or Debian

sudo apt-get update
sudo apt-get install --only-upgrade postgresql-9.6-citus-6.2
sudo service postgresql restart

Fedora, CentOS, or Red Hat

sudo yum update citus62_96
sudo service postgresql-9.6 restart

Major and Minor Version Upgrades

Major and minor version upgrades follow the same steps, but be careful: major upgrades can make backward-incompatible changes in the Citus API. It is best to review the Citus changelog before a major upgrade and look for any changes which may cause problems for your application.

Each major and minor version of Citus is published as a package with a separate name. Installing a newer package will automatically remove the older version. Here is how to upgrade from 6.1 to 6.2 for instance:

Step 1. Update Citus Package

Ubuntu or Debian

sudo apt-get update
sudo apt-get install postgresql-9.6-citus-6.2
sudo service postgresql restart

Fedora, CentOS, or Red Hat

# Fedora, CentOS, or Red Hat
sudo yum swap citus61_96 citus62_96
sudo service postgresql-9.6 restart

Step 2. Apply Update in DB

After installing the new package and restarting the database, run the extension upgrade script.

# you must restart PostgreSQL before running this
psql -c 'ALTER EXTENSION citus UPDATE;'

# you should see the newer Citus version in the list
psql -c '\dx'

Note

During a major version upgrade, from the moment of yum installing a new version, Citus will refuse to run distributed queries until the server is restarted and ALTER EXTENSION is executed. This is to protect your data, as Citus object and function definitions are specific to a version. After a yum install you should (a) restart and (b) run alter extension. In rare cases if you experience an error with upgrades, you can disable this check via the citus.enable_version_checks configuration parameter. You can also contact us providing information about the error, so we can help debug the issue.

Step 3. (upgrade from 5.x only) Add Co-Location Metadata

When doing a major upgrade from Citus 5.x be sure to create metadata for your implicit table co-location. Read more about that in the Upgrading from Citus 5.x section of the co-location page.

Upgrading PostgreSQL version from 9.5 to 9.6

Note

PostgreSQL 9.6 requires using Citus 6.0 or greater. To upgrade PostgreSQL with an older version of Citus, first upgrade Citus as explained in Major and Minor Version Upgrades.

Record the following paths before you start (your actual paths may be different than those below):

Existing data directory (e.g. /opt/pgsql/9.5/data)
export OLD_PG_DATA=/opt/pgsql/9.5/data
Existing PostgreSQL installation path (e.g. /usr/pgsql-9.5)
export OLD_PG_PATH=/usr/pgsql-9.5
New data directory after upgrade
export NEW_PG_DATA=/opt/pgsql/9.6/data
New PostgreSQL installation path
export NEW_PG_PATH=/usr/pgsql-9.6

On the Coordinator Node

  1. If using Citus v5.x follow the previous steps to install Citus 6.0 onto the existing postgresql 9.5 server.
  2. Back up Citus metadata in the old server.
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_shard_placement AS SELECT * FROM pg_catalog.pg_dist_shard_placement;
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;
  1. Configure the new database instance to use Citus.
  • Include Citus as a shared preload library in postgresql.conf:
shared_preload_libraries = 'citus'
  • DO NOT CREATE Citus extension yet
  1. Stop the old and new servers.
  2. Check upgrade compatibility.
$NEW_PG_PATH/bin/pg_upgrade -b $OLD_PG_PATH/bin/ -B $NEW_PG_PATH/bin/ \
                            -d $OLD_PG_DATA -D $NEW_PG_DATA --check

You should see a “Clusters are compatible” message. If you do not, fix any errors before proceeding. Please ensure that

  • NEW_PG_DATA contains an empty database initialized by new PostgreSQL version
  • The Citus extension IS NOT created
  1. Perform the upgrade (like before but without the --check option).
$NEW_PG_PATH/bin/pg_upgrade -b $OLD_PG_PATH/bin/ -B $NEW_PG_PATH/bin/ \
                            -d $OLD_PG_DATA -D $NEW_PG_DATA
  1. Start the new server.
  2. Restore metadata.
INSERT INTO pg_catalog.pg_dist_partition SELECT * FROM public.pg_dist_partition;
INSERT INTO pg_catalog.pg_dist_shard SELECT * FROM public.pg_dist_shard;
INSERT INTO pg_catalog.pg_dist_shard_placement SELECT * FROM public.pg_dist_shard_placement;
INSERT INTO pg_catalog.pg_dist_node SELECT * FROM public.pg_dist_node;
TRUNCATE TABLE pg_catalog.pg_dist_local_group;
INSERT INTO pg_catalog.pg_dist_local_group SELECT * FROM public.pg_dist_local_group;
INSERT INTO pg_catalog.pg_dist_transaction SELECT * FROM public.pg_dist_transaction;
INSERT INTO pg_catalog.pg_dist_colocation SELECT * FROM public.pg_dist_colocation;
  1. Drop temporary metadata tables.
DROP TABLE public.pg_dist_partition;
DROP TABLE public.pg_dist_shard;
DROP TABLE public.pg_dist_shard_placement;
DROP TABLE public.pg_dist_node;
DROP TABLE public.pg_dist_local_group;
DROP TABLE public.pg_dist_transaction;
DROP TABLE public.pg_dist_colocation;
  1. Restart sequences.
SELECT setval('pg_catalog.pg_dist_shardid_seq', (SELECT MAX(shardid)+1 AS max_shard_id FROM pg_dist_shard), false);

SELECT setval('pg_catalog.pg_dist_groupid_seq', (SELECT MAX(groupid)+1 AS max_group_id FROM pg_dist_node), false);

SELECT setval('pg_catalog.pg_dist_node_nodeid_seq', (SELECT MAX(nodeid)+1 AS max_node_id FROM pg_dist_node), false);

SELECT setval('pg_catalog.pg_dist_shard_placement_placementid_seq', (SELECT MAX(placementid)+1 AS max_placement_id FROM pg_dist_shard_placement), false);

SELECT setval('pg_catalog.pg_dist_colocationid_seq', (SELECT MAX(colocationid)+1 AS max_colocation_id FROM pg_dist_colocation), false);
  1. Register triggers.
CREATE OR REPLACE FUNCTION create_truncate_trigger(table_name regclass) RETURNS void LANGUAGE plpgsql as $$
DECLARE
  command  text;
  trigger_name text;

BEGIN
  trigger_name := 'truncate_trigger_' || table_name::oid;
  command := 'create trigger ' || trigger_name || ' after truncate on ' || table_name || ' execute procedure pg_catalog.citus_truncate_trigger()';
  execute command;
  command := 'update pg_trigger set tgisinternal = true where tgname
 = ' || quote_literal(trigger_name);
  execute command;
END;
$$;

SELECT create_truncate_trigger(logicalrelid) FROM pg_dist_partition ;

DROP FUNCTION create_truncate_trigger(regclass);
  1. Set dependencies.
INSERT INTO
  pg_depend
SELECT
  'pg_class'::regclass::oid as classid,
  p.logicalrelid::regclass::oid as objid,
  0 as objsubid,
  'pg_extension'::regclass::oid as refclassid,
  (select oid from pg_extension where extname = 'citus') as refobjid,
  0 as refobjsubid ,
  'n' as deptype
FROM
  pg_dist_partition p;

On Worker Nodes

  1. Install Citus 6.0 onto existing PostgreSQL 9.5 server as outlined in Major and Minor Version Upgrades.
  2. Stop the old and new servers.
  3. Check upgrade compatibility to PostgreSQL 9.6.
$NEW_PG_PATH/bin/pg_upgrade -b $OLD_PG_PATH/bin/ -B $NEW_PG_PATH/bin/ \
                            -d $OLD_PG_DATA -D $NEW_PG_DATA --check

You should see a “Clusters are compatible” message. If you do not, fix any errors before proceeding. Please ensure that

  • NEW_PG_DATA contains an empty database initialized by new PostgreSQL version
  • The Citus extension IS NOT created
  1. Perform the upgrade (like before but without the --check option).
$NEW_PG_PATH/bin/pg_upgrade -b $OLD_PG_PATH/bin/ -B $NEW_PG_PATH/bin/ \
                            -d $OLD_PG_DATA -D $NEW_PG_DATA
  1. Start the new server.