Add id sequence to pending builds table

This change makes it easier to track queuing sequence and the order in
which builds should be processed.

app/models/ci/build.rb

@@ -37,7 +37,7 @@ module Ci
 
     has_one :deployment, as: :deployable, class_name: 'Deployment'
     has_one :pending_state, class_name: 'Ci::BuildPendingState', inverse_of: :build
-    has_one :queuing_entry, class_name: 'Ci::PendingBuild', foreign_key: :build_id, inverse_of: :build
+    has_one :queuing_entry, class_name: 'Ci::PendingBuild', foreign_key: :build_id
     has_many :trace_sections, class_name: 'Ci::BuildTraceSection'
     has_many :trace_chunks, class_name: 'Ci::BuildTraceChunk', foreign_key: :build_id, inverse_of: :build
     has_many :report_results, class_name: 'Ci::BuildReportResult', inverse_of: :build

app/models/ci/pending_build.rb

@@ -5,14 +5,18 @@ module Ci
     extend Gitlab::Ci::Model
 
     belongs_to :project
-    belongs_to :build, class_name: 'Ci::Build', inverse_of: :queuing_entry
+    belongs_to :build, class_name: 'Ci::Build'
 
     def self.upsert!(build)
       entry = self.new(build: build, project: build.project)
 
       raise ArgumentError, 'queuing entry invalid' unless entry.valid?
 
-      upsert({ build_id: entry.build_id, project_id: entry.project_id })
+      attributes = { build_id: entry.build_id, project_id: entry.project_id }
+
+      ActiveRecord::InsertAll
+        .new(self, [attributes], on_duplicate: :skip, returning: %w[build_id])
+        .execute
     end
   end
 end

db/migrate/20210512120122_add_pending_builds_table.rb

@@ -2,8 +2,8 @@
 
 class AddPendingBuildsTable < ActiveRecord::Migration[6.0]
   def up
-    create_table :ci_pending_builds, id: false do |t|
-      t.references :build, primary_key: true, default: nil, index: false, foreign_key: { to_table: :ci_builds, on_delete: :cascade }
+    create_table :ci_pending_builds do |t|
+      t.references :build, index: { unique: true }, null: false, foreign_key: { to_table: :ci_builds, on_delete: :cascade }
       t.references :project, index: true, null: false, foreign_key: { on_delete: :cascade }
       t.datetime_with_timezone :created_at, null: false, default: -> { 'NOW()' }
     end

db/structure.sql

@@ -10753,11 +10753,21 @@ CREATE SEQUENCE ci_namespace_monthly_usages_id_seq
 ALTER SEQUENCE ci_namespace_monthly_usages_id_seq OWNED BY ci_namespace_monthly_usages.id;
 
 CREATE TABLE ci_pending_builds (
+    id bigint NOT NULL,
     build_id bigint NOT NULL,
     project_id bigint NOT NULL,
     created_at timestamp with time zone DEFAULT now() NOT NULL
 );
 
+CREATE SEQUENCE ci_pending_builds_id_seq
+    START WITH 1
+    INCREMENT BY 1
+    NO MINVALUE
+    NO MAXVALUE
+    CACHE 1;
+
+ALTER SEQUENCE ci_pending_builds_id_seq OWNED BY ci_pending_builds.id;
+
 CREATE TABLE ci_pipeline_artifacts (
     id bigint NOT NULL,
     created_at timestamp with time zone NOT NULL,
@@ -19474,6 +19484,8 @@ ALTER TABLE ONLY ci_job_variables ALTER COLUMN id SET DEFAULT nextval('ci_job_va
 
 ALTER TABLE ONLY ci_namespace_monthly_usages ALTER COLUMN id SET DEFAULT nextval('ci_namespace_monthly_usages_id_seq'::regclass);
 
+ALTER TABLE ONLY ci_pending_builds ALTER COLUMN id SET DEFAULT nextval('ci_pending_builds_id_seq'::regclass);
+
 ALTER TABLE ONLY ci_pipeline_artifacts ALTER COLUMN id SET DEFAULT nextval('ci_pipeline_artifacts_id_seq'::regclass);
 
 ALTER TABLE ONLY ci_pipeline_chat_data ALTER COLUMN id SET DEFAULT nextval('ci_pipeline_chat_data_id_seq'::regclass);
@@ -20645,7 +20657,7 @@ ALTER TABLE ONLY ci_namespace_monthly_usages
     ADD CONSTRAINT ci_namespace_monthly_usages_pkey PRIMARY KEY (id);
 
 ALTER TABLE ONLY ci_pending_builds
-    ADD CONSTRAINT ci_pending_builds_pkey PRIMARY KEY (build_id);
+    ADD CONSTRAINT ci_pending_builds_pkey PRIMARY KEY (id);
 
 ALTER TABLE ONLY ci_pipeline_artifacts
     ADD CONSTRAINT ci_pipeline_artifacts_pkey PRIMARY KEY (id);
@@ -22534,6 +22546,8 @@ CREATE UNIQUE INDEX index_ci_job_variables_on_key_and_job_id ON ci_job_variables
 
 CREATE UNIQUE INDEX index_ci_namespace_monthly_usages_on_namespace_id_and_date ON ci_namespace_monthly_usages USING btree (namespace_id, date);
 
+CREATE UNIQUE INDEX index_ci_pending_builds_on_build_id ON ci_pending_builds USING btree (build_id);
+
 CREATE INDEX index_ci_pending_builds_on_project_id ON ci_pending_builds USING btree (project_id);
 
 CREATE INDEX index_ci_pipeline_artifacts_failed_verification ON ci_pipeline_artifacts USING btree (verification_retry_at NULLS FIRST) WHERE (verification_state = 3);

spec/services/ci/update_build_queue_service_spec.rb

@@ -47,10 +47,10 @@ RSpec.describe Ci::UpdateBuildQueueService do
         ::Ci::PendingBuild.create!(build: build, project: project)
       end
 
-      it 'does nothing and returns updated build id' do
+      it 'does nothing and returns nil' do
         queued = subject.push(build, transition)
 
-        expect(queued).to eq build.id
+        expect(queued).to be_nil
       end
     end
   end