Re: Foreign Key error between two partitioned tables

On Fri, 19 Apr 2024 at 05:48, Michael Corey
<michael(dot)corey(dot)ap(at)nielsen(dot)com> wrote:
> ALTER TABLE ONLY par_log_file
> ADD CONSTRAINT plf_pk PRIMARY KEY (par_file_id);

> ALTER TABLE par_log_definition
> ADD CONSTRAINT pld_fk FOREIGN KEY (par_file_id) REFERENCES par_log_file(par_file_id);

> I receive the following error when creating a foreign key between two partitioned tables.
> ERROR: there is no unique constraint matching given keys for referenced table "par_log_file"

> Version Postgres 13.13

No problems running that script here on 13.13. I imagine you've
probably got a partition attached to par_log_file already and since
your "plf_pk" constraint is on ONLY par_log_file, then the supporting
index is likely invalid.

I'd suggest checking if this is the case with:

select indexrelid::regclass,indisvalid from pg_index where indrelid =
'par_log_file'::regclass;

The correct way to create the PK constraint is with:

ALTER TABLE par_log_file ADD CONSTRAINT plf_pk PRIMARY KEY (par_file_id);

You might want to create supporting unique indexes on each partition
CONCURRENTLY before doing that so that the ALTER TABLE becomes a
meta-data-only operation.

David