31.4. Column Lists #

31.4.1. Combining Multiple Column Lists
31.4.2. Examples

Each publication can optionally specify which columns of each table are replicated to subscribers. The table on the subscriber side must have at least all the columns that are published. If no column list is specified, then all columns on the publisher are replicated. See CREATE PUBLICATION for details on the syntax.

The choice of columns can be based on behavioral or performance reasons. However, do not rely on this feature for security: a malicious subscriber is able to obtain data from columns that are not specifically published. If security is a consideration, protections can be applied at the publisher side.

If no column list is specified, any columns added later are automatically replicated. This means that having a column list which names all columns is not the same as having no column list at all.

A column list can contain only simple column references. The order of columns in the list is not preserved.

Specifying a column list when the publication also publishes FOR TABLES IN SCHEMA is not supported.

For partitioned tables, the publication parameter publish_via_partition_root determines which column list is used. If publish_via_partition_root is true, the root partitioned table's column list is used. Otherwise, if publish_via_partition_root is false (the default), each partition's column list is used.

If a publication publishes UPDATE or DELETE operations, any column list must include the table's replica identity columns (see REPLICA IDENTITY). If a publication publishes only INSERT operations, then the column list may omit replica identity columns.

Column lists have no effect for the TRUNCATE command.

During initial data synchronization, only the published columns are copied. However, if the subscriber is from a release prior to 15, then all the columns in the table are copied during initial data synchronization, ignoring any column lists.

31.4.1. Combining Multiple Column Lists #


It is not supported to have a subscription comprising several publications where the same table has been published with different column lists. This means changing the column lists of the tables being subscribed could cause inconsistency of column lists among publications, in which case the ALTER PUBLICATION will be successful but later the walsender on the publisher, or the subscriber may throw an error. In this scenario, the user needs to recreate the subscription after adjusting the column list or drop the problematic publication using ALTER SUBSCRIPTION ... DROP PUBLICATION and then add it back after adjusting the column list.

31.4.2. Examples #

Create a table t1 to be used in the following example.

test_pub=# CREATE TABLE t1(id int, a text, b text, c text, d text, e text, PRIMARY KEY(id));

Create a publication p1. A column list is defined for table t1 to reduce the number of columns that will be replicated. Notice that the order of column names in the column list does not matter.

test_pub=# CREATE PUBLICATION p1 FOR TABLE t1 (id, b, a, d);

psql can be used to show the column lists (if defined) for each publication.

test_pub=# \dRp+
                               Publication p1
  Owner   | All tables | Inserts | Updates | Deletes | Truncates | Via root
 postgres | f          | t       | t       | t       | t         | f
    "public.t1" (id, a, b, d)

psql can be used to show the column lists (if defined) for each table.

test_pub=# \d t1
                 Table "public.t1"
 Column |  Type   | Collation | Nullable | Default
 id     | integer |           | not null |
 a      | text    |           |          |
 b      | text    |           |          |
 c      | text    |           |          |
 d      | text    |           |          |
 e      | text    |           |          |
    "t1_pkey" PRIMARY KEY, btree (id)
    "p1" (id, a, b, d)

On the subscriber node, create a table t1 which now only needs a subset of the columns that were on the publisher table t1, and also create the subscription s1 that subscribes to the publication p1.

test_sub=# CREATE TABLE t1(id int, b text, a text, d text, PRIMARY KEY(id));
test_sub-# CONNECTION 'host=localhost dbname=test_pub application_name=s1'
test_sub-# PUBLICATION p1;

On the publisher node, insert some rows to table t1.

test_pub=# INSERT INTO t1 VALUES(1, 'a-1', 'b-1', 'c-1', 'd-1', 'e-1');
test_pub=# INSERT INTO t1 VALUES(2, 'a-2', 'b-2', 'c-2', 'd-2', 'e-2');
test_pub=# INSERT INTO t1 VALUES(3, 'a-3', 'b-3', 'c-3', 'd-3', 'e-3');
test_pub=# SELECT * FROM t1 ORDER BY id;
 id |  a  |  b  |  c  |  d  |  e
  1 | a-1 | b-1 | c-1 | d-1 | e-1
  2 | a-2 | b-2 | c-2 | d-2 | e-2
  3 | a-3 | b-3 | c-3 | d-3 | e-3
(3 rows)

Only data from the column list of publication p1 is replicated.

test_sub=# SELECT * FROM t1 ORDER BY id;
 id |  b  |  a  |  d
  1 | b-1 | a-1 | d-1
  2 | b-2 | a-2 | d-2
  3 | b-3 | a-3 | d-3
(3 rows)