add check against using NOT VALID, VALIDATE in same transaction

[chdsbd]

Adding a constraint as NOT VALID and running VALIDATE CONSTRAINT in the same transaction is equivalent to adding the constraint without NOT VALID. Reads will be blocked while the table is scanned to validate the constraint.

The solution is to add the constraint as NOT VALID in one transaction and VALIDATE CONSTRAINT in a separate transaction.

Example bad migration

BEGIN;
ALTER TABLE "app_email" ADD CONSTRAINT "fk_user" FOREIGN KEY (user_id) REFERENCES "app_user" (id) NOT VALID;
ALTER TABLE "app_email" VALIDATE CONSTRAINT "fk_user";
COMMIT;

Example warning

stdin:1:0: warning: constraint-missing-not-valid

   1 | BEGIN;
   2 | ALTER TABLE "app_email" ADD CONSTRAINT "fk_user" FOREIGN KEY (user_id) REFERENCES "app_user" (id) NOT VALID;
   3 | ALTER TABLE "app_email" VALIDATE CONSTRAINT "fk_user";
   4 | COMMIT;

  note: Using NOT VALID and VALIDATE CONSTRAINT in the same transaction will block all reads while the constraint is validated.
  help: Add constraint as NOT VALID in one transaction and VALIDATE CONSTRAINT in a separate transaction.

Fixed SQL

BEGIN;
ALTER TABLE "app_email" ADD CONSTRAINT "fk_user" FOREIGN KEY (user_id) REFERENCES "app_user" (id) NOT VALID;
COMMIT;
BEGIN;
ALTER TABLE "app_email" VALIDATE CONSTRAINT "fk_user";
COMMIT;

Result

Found 0 issues in 1 file 🎉