BLOB storage in Postgres databases
To improve performance of Postgres databases, BLOB columns in new tables that are created during installation, upgrade, or DDL (Data Definition Language) and schema generation are altered to use external storage instead of expanded storage. Existing tables with BLOB columns are not altered during an upgrade. System management utilities that create tables with BLOB columns, such as import, still default to use expanded storage.
You can alter existing tables to use external storage when new data is inserted into them by using the following command:
alter table <schema name>.<table_name> alter column <column name> set storage external