use unique index and separate database migration

Signed-off-by: Ryan Li <[email protected]>

db/migration/202009171251-init-database.go

@@ -77,9 +77,6 @@ CREATE TABLE IF NOT EXISTS workflow_worker_map (
         , worker_id UUID NOT NULL
 );
 
-ALTER TABLE workflow_worker_map DROP CONSTRAINT IF EXISTS workflow_worker_pkey;
-ALTER TABLE workflow_worker_map ADD CONSTRAINT workflow_worker_pkey PRIMARY KEY (workflow_id, worker_id);
-
 CREATE TABLE IF NOT EXISTS workflow_data (
         workflow_id UUID NOT NULL
         , version INT

db/migration/202010221010-add-unique-index.go

@@ -0,0 +1,12 @@
+package migration
+
+import migrate "github.com/rubenv/sql-migrate"
+
+func Get202010221010() *migrate.Migration {
+        return &migrate.Migration{
+                Id: "202010221010-add-unique-index",
+                Up: []string{`
+CREATE UNIQUE INDEX IF NOT EXISTS uidx_workflow_worker_map ON workflow_worker_map (workflow_id, worker_id);
+`},
+        }
+}

db/migration/migration.go

@@ -6,6 +6,7 @@ func GetMigrations() *migrate.MemoryMigrationSource {
 	return &migrate.MemoryMigrationSource{
 		Migrations: []*migrate.Migration{
 			Get202009171251(),
+			Get202010221010(),
 		},
 	}
 }