disallowed-unique-constraint

What It Detects

Adding a UNIQUE constraint without USING INDEX scans the entire table under ACCESS EXCLUSIVE.

Why It's Dangerous

ADD CONSTRAINT UNIQUE builds a unique index while holding ACCESS EXCLUSIVE. Instead, create a unique index CONCURRENTLY first, then add the constraint USING INDEX.

Bad Example

ALTER TABLE users ADD CONSTRAINT uq_email UNIQUE (email);

Good Example

CREATE UNIQUE INDEX CONCURRENTLY uq_email ON users (email);
ALTER TABLE users ADD CONSTRAINT uq_email UNIQUE USING INDEX uq_email;

Configuration

Disable this rule:

# .migrationpilotrc.yml
rules:
  MP027: false

Or change its severity:

# .migrationpilotrc.yml
rules:
  MP027:
    severity: warning