Reduce batch size

…to stay within our query timeout of 60s. Also reduce the job interval to keep the same overall migration time of ~3.3 days.

db/post_migrate/20170907170235_delete_conflicting_redirect_routes.rb

@@ -6,6 +6,8 @@ class DeleteConflictingRedirectRoutes < ActiveRecord::Migration
 
   DOWNTIME = false
   MIGRATION = 'DeleteConflictingRedirectRoutesRange'.freeze
+  BATCH_SIZE = 200 # At 200, I expect under 20s per batch, which is under our query timeout of 60s.
+  DELAY_INTERVAL = 12.seconds
 
   disable_ddl_transaction!
 
@@ -18,7 +20,7 @@ class DeleteConflictingRedirectRoutes < ActiveRecord::Migration
   def up
     say opening_message
 
-    queue_background_migration_jobs_by_range_at_intervals(Route, MIGRATION, 1.minute)
+    queue_background_migration_jobs_by_range_at_intervals(Route, MIGRATION, DELAY_INTERVAL, batch_size: BATCH_SIZE)
   end
 
   def down

spec/migrations/delete_conflicting_redirect_routes_spec.rb

@@ -10,7 +10,7 @@ describe DeleteConflictingRedirectRoutes, :migration, :sidekiq do
   end
 
   before do
-    stub_const("Gitlab::Database::MigrationHelpers::BACKGROUND_MIGRATION_BATCH_SIZE", 2)
+    stub_const("DeleteConflictingRedirectRoutes::BATCH_SIZE", 2)
     stub_const("Gitlab::Database::MigrationHelpers::BACKGROUND_MIGRATION_JOB_BUFFER_SIZE", 2)
 
     routes.create!(id: 1, source_id: 1, source_type: 'Namespace', path: 'foo1')
@@ -38,11 +38,11 @@ describe DeleteConflictingRedirectRoutes, :migration, :sidekiq do
         migrate!
 
         expect(BackgroundMigrationWorker.jobs[0]['args']).to eq([described_class::MIGRATION, [1, 2]])
-        expect(BackgroundMigrationWorker.jobs[0]['at']).to eq(1.minute.from_now.to_f)
+        expect(BackgroundMigrationWorker.jobs[0]['at']).to eq(12.seconds.from_now.to_f)
         expect(BackgroundMigrationWorker.jobs[1]['args']).to eq([described_class::MIGRATION, [3, 4]])
-        expect(BackgroundMigrationWorker.jobs[1]['at']).to eq(2.minutes.from_now.to_f)
+        expect(BackgroundMigrationWorker.jobs[1]['at']).to eq(24.seconds.from_now.to_f)
         expect(BackgroundMigrationWorker.jobs[2]['args']).to eq([described_class::MIGRATION, [5, 5]])
-        expect(BackgroundMigrationWorker.jobs[2]['at']).to eq(3.minutes.from_now.to_f)
+        expect(BackgroundMigrationWorker.jobs[2]['at']).to eq(36.seconds.from_now.to_f)
         expect(BackgroundMigrationWorker.jobs.size).to eq 3
       end
     end