Typically, a table at the subscriber will be defined the same as the publisher table, so if the publisher table has a GENERATED column then the subscriber table will have a matching generated column. In this case, it is always the subscriber table generated column value that is used.

For example, note below that subscriber table generated column value comes from the subscriber column's calculation.

test_pub=# CREATE TABLE tab_gen_to_gen (a int, b int GENERATED ALWAYS AS (a + 1) STORED);
CREATE TABLE
test_pub=# INSERT INTO tab_gen_to_gen VALUES (1),(2),(3);
INSERT 0 3
test_pub=# CREATE PUBLICATION pub1 FOR TABLE tab_gen_to_gen;
CREATE PUBLICATION
test_pub=# SELECT * FROM tab_gen_to_gen;
 a | b
---+---
 1 | 2
 2 | 3
 3 | 4
(3 rows)

test_sub=# CREATE TABLE tab_gen_to_gen (a int, b int GENERATED ALWAYS AS (a * 100) STORED);
CREATE TABLE
test_sub=# CREATE SUBSCRIPTION sub1 CONNECTION 'dbname=test_pub' PUBLICATION pub1;
CREATE SUBSCRIPTION
test_sub=# SELECT * from tab_gen_to_gen;
 a | b
---+----
 1 | 100
 2 | 200
 3 | 300
(3 rows)

In fact, prior to version 18.0, logical replication does not publish GENERATED columns at all.

But, replicating a generated column to a regular column can sometimes be desirable.

Generated columns are not published by default, but users can opt to publish stored generated columns just like regular ones.

There are two ways to do this:

The following table summarizes behavior when there are generated columns involved in the logical replication. Results are shown for when publishing generated columns is not enabled, and for when it is enabled.