Fix migrations for older PostgreSQL versions

- Do not care about error when creating index on PostgreSQL
- Test against PostgreSQL 9.2

.gitlab-ci.yml

@@ -52,7 +52,7 @@ stages:
 
 .use-pg: &use-pg
   services:
-    - postgres:latest
+    - postgres:9.2
     - redis:alpine
 
 .use-mysql: &use-mysql

changelogs/unreleased/fix-migration-for-postgres.yml

+---
+title: Fix migration for older PostgreSQL versions
+merge_request:
+author:

db/post_migrate/20170503004427_upate_retried_for_ci_build.rb → db/post_migrate/20170503004427_update_retried_for_ci_build.rb

-class UpateRetriedForCiBuild < ActiveRecord::Migration
+class UpdateRetriedForCiBuild < ActiveRecord::Migration
   include Gitlab::Database::MigrationHelpers
 
   DOWNTIME = false
@@ -54,13 +54,15 @@ class UpateRetriedForCiBuild < ActiveRecord::Migration
 
   def with_temporary_partial_index
     if Gitlab::Database.postgresql?
-      execute 'CREATE INDEX CONCURRENTLY IF NOT EXISTS index_for_ci_builds_retried_migration ON ci_builds (id) WHERE retried IS NULL;'
+      unless index_exists?(:ci_builds, name: :index_for_ci_builds_retried_migration)
+        execute 'CREATE INDEX CONCURRENTLY index_for_ci_builds_retried_migration ON ci_builds (id) WHERE retried IS NULL;'
+      end
     end
 
     yield
 
-    if Gitlab::Database.postgresql?
-      execute 'DROP INDEX CONCURRENTLY IF EXISTS index_for_ci_builds_retried_migration'
+    if Gitlab::Database.postgresql? && index_exists?(:ci_builds, name: :index_for_ci_builds_retried_migration)
+      execute 'DROP INDEX CONCURRENTLY index_for_ci_builds_retried_migration'
     end
   end
 end

spec/migrations/upate_retried_for_ci_builds_spec.rb → spec/migrations/update_retried_for_ci_builds_spec.rb

 require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20170503004427_upate_retried_for_ci_build.rb')
+require Rails.root.join('db', 'post_migrate', '20170503004427_update_retried_for_ci_build.rb')
 
-describe UpateRetriedForCiBuild, truncate: true do
+describe UpdateRetriedForCiBuild, truncate: true do
   let(:pipeline) { create(:ci_pipeline) }
   let!(:build_old) { create(:ci_build, pipeline: pipeline, name: 'test') }
   let!(:build_new) { create(:ci_build, pipeline: pipeline, name: 'test') }