Actually add the system module

guix-data-service/model/system.scm

@@ -0,0 +1,57 @@
+;;; Guix Data Service -- Information about Guix over time
+;;; Copyright © 2019, 2020, 2021 Christopher Baines <mail@cbaines.net>
+;;;
+;;; This program is free software: you can redistribute it and/or
+;;; modify it under the terms of the GNU Affero General Public License
+;;; as published by the Free Software Foundation, either version 3 of
+;;; the License, or (at your option) any later version.
+;;;
+;;; This program is distributed in the hope that it will be useful,
+;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+;;; Affero General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU Affero General Public
+;;; License along with this program.  If not, see
+;;; <http://www.gnu.org/licenses/>.
+
+(define-module (guix-data-service model system)
+  #:use-module (srfi srfi-1)
+  #:use-module (ice-9 vlist)
+  #:use-module (ice-9 match)
+  #:use-module (squee)
+  #:use-module (guix-data-service model utils)
+  #:export (system->system-id
+            list-systems))
+
+(define system->system-id-cache
+  (make-hash-table))
+
+(define systems-cache #f)
+
+(define (system->system-id conn system)
+  (let ((cached-value (hash-ref system->system-id-cache
+                                system)))
+    (or cached-value
+        (match (insert-missing-data-and-return-all-ids
+                conn
+                "systems"
+                '(system)
+                `((,system)))
+          ((id)
+           (hash-set! system->system-id-cache
+                      system
+                      id)
+           (set! systems-cache #f)
+           id)))))
+
+(define (list-systems conn)
+  (if systems-cache
+      systems-cache
+      (let ((systems
+             (map car
+                  (exec-query
+                   conn
+                   "SELECT system FROM systems ORDER BY system"))))
+        (set! systems-cache systems)
+        systems)))