module Sequel::Plugins::PgAutoConstraintValidations

  1. lib/sequel/plugins/pg_auto_constraint_validations.rb

The pg_auto_constraint_validations plugin automatically converts some constraint violation exceptions that are raised by INSERT/UPDATE queries into validation failures. This can allow for using the same error handling code for both regular validation errors (checked before attempting the INSERT/UPDATE), and constraint violations (raised during the INSERT/UPDATE).

This handles the following constraint violations:

  • NOT NULL

  • CHECK

  • UNIQUE (except expression/functional indexes)

  • FOREIGN KEY (both referencing and referenced by)

If the plugin cannot convert the constraint violation error to a validation error, it just reraises the initial exception, so this should not cause problems if the plugin doesn't know how to convert the exception.

This plugin is not intended as a replacement for other validations, it is intended as a last resort. The purpose of validations is to provide nice error messages for the user, and the error messages generated by this plugin are fairly generic by default. The error messages can be customized per constraint type using the :messages plugin option, and individually per constraint using pg_auto_constraint_validation_override (see below).

This plugin only works on the postgres adapter when using the pg 0.16+ driver, PostgreSQL 9.3+ server, and PostgreSQL 9.3+ client library (libpq). In other cases it will be a no-op.

Example:

album = Album.new(:artist_id=>1) # Assume no such artist exists
begin
  album.save
rescue Sequel::ValidationFailed
  album.errors.on(:artist_id) # ['is invalid']
end

While the database usually provides enough information to correctly associated constraint violations with model columns, there are cases where it does not. In those cases, you can override the handling of specific constraint violations to be associated to particular column(s), and use a specific error message:

Album.pg_auto_constraint_validation_override(:constraint_name, [:column1], "validation error message")

Usage:

# Make all model subclasses automatically convert constraint violations
# to validation failures (called before loading subclasses)
Sequel::Model.plugin :pg_auto_constraint_validations

# Make the Album class automatically convert constraint violations
# to validation failures
Album.plugin :pg_auto_constraint_validations

Methods

Public Class

  1. configure

Constants

DEFAULT_ERROR_MESSAGES = { :not_null=>"is not present", :check=>"is invalid", :unique=>'is already taken', :foreign_key=>'is invalid', :referenced_by=>'cannot be changed currently' }.freeze).each_value(&:freeze)  

The default error messages for each constraint violation type.

Public Class methods

configure (model, opts=OPTS)

Setup the constraint violation metadata. Options:

:messages

Override the default error messages for each constraint violation type (:not_null, :check, :unique, :foreign_key, :referenced_by)

[show source]
   # File lib/sequel/plugins/pg_auto_constraint_validations.rb
72 def self.configure(model, opts=OPTS)
73   model.instance_exec do
74     setup_pg_auto_constraint_validations
75     @pg_auto_constraint_validations_messages = (@pg_auto_constraint_validations_messages || DEFAULT_ERROR_MESSAGES).merge(opts[:messages] || OPTS).freeze
76   end
77 end