Jobsets: add a SERIAL, unique, non-null id column

A postgresql column which is non-null and unique is treated with
the same optimisations as a primary key, so we have no need to
try and recreate the `id` as the primary key.

No read paths are impacted by this change, and the database will
automatically create an ID for each insert. Thus, no code needs to
change.

src/lib/Hydra/Schema/Jobsets.pm

@@ -40,6 +40,13 @@ __PACKAGE__->table("jobsets");
   data_type: 'text'
   is_nullable: 0
 
+=head2 id
+
+  data_type: 'integer'
+  is_auto_increment: 1
+  is_nullable: 0
+  sequence: 'jobsets_id_seq'
+
 =head2 project
 
   data_type: 'text'
@@ -153,6 +160,13 @@ __PACKAGE__->table("jobsets");
 __PACKAGE__->add_columns(
   "name",
   { data_type => "text", is_nullable => 0 },
+  "id",
+  {
+    data_type         => "integer",
+    is_auto_increment => 1,
+    is_nullable       => 0,
+    sequence          => "jobsets_id_seq",
+  },
   "project",
   { data_type => "text", is_foreign_key => 1, is_nullable => 0 },
   "description",
@@ -209,6 +223,20 @@ __PACKAGE__->add_columns(
 
 __PACKAGE__->set_primary_key("project", "name");
 
+=head1 UNIQUE CONSTRAINTS
+
+=head2 C<jobsets_id_unique>
+
+=over 4
+
+=item * L</id>
+
+=back
+
+=cut
+
+__PACKAGE__->add_unique_constraint("jobsets_id_unique", ["id"]);
+
 =head1 RELATIONS
 
 =head2 buildmetrics
@@ -350,8 +378,12 @@ __PACKAGE__->has_many(
 );
 
 
-# Created by DBIx::Class::Schema::Loader v0.07049 @ 2020-02-09 15:21:11
-# DO NOT MODIFY THIS OR ANYTHING ABOVE! md5sum:FVP1/AWjdKTlY6djrG592A
+# Created by DBIx::Class::Schema::Loader v0.07049 @ 2020-02-09 15:25:17
+# DO NOT MODIFY THIS OR ANYTHING ABOVE! md5sum:1CMOaLf9fYRdJBlYiivmxA
+
+__PACKAGE__->add_column(
+    "+id" => { retrieve_on_insert => 1 }
+);
 
 my %hint = (
     columns => [

src/sql/hydra.sql

@@ -52,6 +52,7 @@ create table ProjectMembers (
 -- describing build jobs.
 create table Jobsets (
     name          text not null,
+    id            serial not null,
     project       text not null,
     description   text,
     nixExprInput  text, -- name of the jobsetInput containing the Nix or Guix expression
@@ -76,7 +77,8 @@ create table Jobsets (
     check ((type = 0) = (nixExprInput is not null and nixExprPath is not null)),
     check ((type = 1) = (flake is not null)),
     primary key   (project, name),
-    foreign key   (project) references Projects(name) on delete cascade on update cascade
+    foreign key   (project) references Projects(name) on delete cascade on update cascade,
+    constraint    Jobsets_id_unique UNIQUE(id)
 #ifdef SQLITE
     ,
     foreign key   (project, name, nixExprInput) references JobsetInputs(project, jobset, name)

src/sql/upgrade-59.sql

@@ -0,0 +1,4 @@
+-- will automatically add unique IDs to Jobsets.
+ALTER TABLE Jobsets
+  ADD COLUMN id SERIAL NOT NULL,
+  ADD CONSTRAINT Jobsets_id_unique UNIQUE (id);