banDropConstraint¶

Group destructive · Migrations only · Since Unreleased
Diagnostic lint/banDropConstraint

Sources: inspired by squawk/ban-drop-constraint

Description¶

Dropping a constraint may break existing clients.

A constraint is a guarantee that clients can depend on. For example, an application that uses INSERT ... ON CONFLICT ON CONSTRAINT my_constraint, or whose ON CONFLICT (col) relies on a unique constraint, fails as soon as the constraint is gone.

Update clients to no longer depend on the constraint before dropping it.

Examples¶

Invalid¶

alter table users drop constraint users_email_key;

code-block.sql:1:19 lint/banDropConstraint ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! Dropping constraint users_email_key may break existing clients.

  > 1 │ alter table users drop constraint users_email_key;
      │                   ^^^^^^^^^^^^^^^
    2 │ 

  i Clients may depend on the guarantee of the constraint, e.g. as the arbiter of INSERT ... ON CONFLICT.

  i Update clients to no longer depend on the constraint, then drop it in a later migration.

alter domain positive_int drop constraint positive_int_check;

code-block.sql:1:27 lint/banDropConstraint ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! Dropping constraint positive_int_check may break existing clients.

  > 1 │ alter domain positive_int drop constraint positive_int_check;
      │                           ^^^^^^^^^^^^^^^
    2 │ 

  i Clients may depend on the guarantee of the constraint, e.g. as the arbiter of INSERT ... ON CONFLICT.

  i Update clients to no longer depend on the constraint, then drop it in a later migration.

How to configure¶

{
  "linter": {
    "rules": {
      "banDropConstraint": "error"
    }
  }
}

How to suppress¶

Suppress this diagnostic with a comment:

-- pgls-ignore banDropConstraint