Speeding up adding fky on a very large table

[Ravi Krishna <s_ravikrishna@xxxxxxx>]

AWS Aurora based on PG 13.

Large partitioned table of 5+ billion rows and 7TB in size.

ALTER TABLE abc ADD CONSTRAINT fk_123 FOREIGN KEY (a,b,c) REFERENCES xyz(1,2,3);

It seems this is not parallelized. Is there a way. Or directly going into each partition is the only way ( not even sure it is possible).