Add default value to vulnerabilities_allowed column

db/migrate/20210818220234_add_default_project_approval_rules_vuln_allowed.rb

+# frozen_string_literal: true
+
+class AddDefaultProjectApprovalRulesVulnAllowed < ActiveRecord::Migration[6.1]
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  DEFAULT_VALUE = 0
+
+  def up
+    change_column_default :approval_project_rules, :vulnerabilities_allowed, DEFAULT_VALUE
+
+    update_column_in_batches(:approval_project_rules, :vulnerabilities_allowed, DEFAULT_VALUE) do |table, query|
+      query.where(table[:vulnerabilities_allowed].eq(nil))
+    end
+
+    change_column_null :approval_project_rules, :vulnerabilities_allowed, false
+  end
+
+  def down
+    change_column_default :approval_project_rules, :vulnerabilities_allowed, nil
+    change_column_null :approval_project_rules, :vulnerabilities_allowed, true
+  end
+end

db/schema_migrations/20210818220234

+8d247218468ad383d1a8a2dc67d5e7e67ddad2a33a38203a41e49c4c018adc7e
\ No newline at end of file

db/structure.sql

@@ -9746,7 +9746,7 @@ CREATE TABLE approval_project_rules (
     name character varying NOT NULL,
     rule_type smallint DEFAULT 0 NOT NULL,
     scanners text[],
-    vulnerabilities_allowed smallint,
+    vulnerabilities_allowed smallint DEFAULT 0 NOT NULL,
     severity_levels text[] DEFAULT '{}'::text[] NOT NULL
 );

spec/migrations/add_default_project_approval_rules_vuln_allowed_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+require_migration!
+
+RSpec.describe AddDefaultProjectApprovalRulesVulnAllowed do
+  let(:namespaces) { table(:namespaces) }
+  let(:projects) { table(:projects) }
+  let(:namespace) { namespaces.create!(name: 'namespace', path: 'namespace') }
+  let(:project) { projects.create!(name: 'project', path: 'project', namespace_id: namespace.id) }
+  let(:approval_project_rules) { table(:approval_project_rules) }
+
+  it 'updates records when vulnerabilities_allowed is nil' do
+    records_to_migrate = 10
+
+    records_to_migrate.times do |i|
+      approval_project_rules.create!(name: "rule #{i}", project_id: project.id)
+    end
+
+    expect { migrate! }
+      .to change { approval_project_rules.where(vulnerabilities_allowed: nil).count }
+        .from(records_to_migrate)
+        .to(0)
+  end
+
+  it 'defaults vulnerabilities_allowed to 0' do
+    approval_project_rule = approval_project_rules.create!(name: "new rule", project_id: project.id)
+
+    expect(approval_project_rule.vulnerabilities_allowed).to be_nil
+
+    migrate!
+
+    expect(approval_project_rule.reload.vulnerabilities_allowed).to eq(0)
+  end
+end