Subject: Foreign Key error between two partitioned tables

From: Michael Corey <[email-masked]>
Date: Thu, 18 Apr 2024 13:47:19 -0400

Hello,

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"

Here is my setup:

CREATE TABLE par_log_file (
    par_file_id character varying(20) NOT NULL,
    par_id character varying(64) NOT NULL
) PARTITION BY RANGE (par_file_id)  ;

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

--

CREATE TABLE par_log_definition (
    par_file_id character varying(20) NOT NULL,
    tif_seq_nmbr bigint NOT NULL,
    name_25 character varying(255)
) PARTITION BY RANGE (par_file_id)  ;

ALTER TABLE ONLY par_log_definition
    ADD CONSTRAINT pld_pk PRIMARY KEY (par_file_id, tif_seq_nmbr);

CREATE INDEX pld_idx ON par_log_definition USING btree (par_file_id);

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

Version Postgres 13.13

Any help would be appreciated/

-- 
Michael Corey

---

From: David Rowley <[email-masked]>
Date: Sat, 20 Apr 2024 11:19:47 +1200

>     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