Add INCLUDE term to primary key index in Postgres 11

Question

I work with Postgres 11 and would like to change the index that backs the primary key of a large table (~750 million rows). The primary key is the bigint column id and I would like to include an extra column using the INCLUDE term. This needs to happen without a table rewrite (i.e. no new/changed columns).

Dropping the current PRIMARY KEY constraint isn't convenient, because a lot of other tables reference the target table. I suppose it would be possible to drop the FOREIGN KEY constraints on all those tables, then drop the PRIMARY KEY constraint, recreate using a new index and then recreate the FOREIGN KEY constraints. Is there a better way to do it?

Answer 1

Without messing with the catalogs (which is not commendable), the only option I can think of would require you to do without foreign keys for a while:

You can define a second UNIQUE index on the table that contains the appropriate INCLUDE clause.

If you use the CONCURRENTLY clause of CREATE INDEX, that shouldn't be disruptive.

Then you can delete the original primary key constraint and all dependent foreign keys using DROP INDEX ... CASCADE.

Then use ALTER TABLE ... ADD CONSTRAINT ... USING INDEX to turn the unique index into a primary key constraint.

Now you can re-create the foreign key constraints.