Re-arrange some of the load new revision code

Try to isolate the code that inserts in to the database, so that the relevant
tables can be locked during this time.

guix-data-service/jobs/load-new-guix-revision.scm

@@ -196,7 +196,15 @@
                              (lambda ()
                                (deduplicate-inferior-packages
                                 (inferior-packages inf)))))
-         (package-license-set-ids
+         (inferior-data-4-tuples
+          (log-time "getting inferior derivations"
+                    (lambda ()
+                      (all-inferior-package-derivations store inf packages)))))
+
+    (define loading-inferior-data
+      (record-start-time "critical region fetching and loading inferior data"))
+
+    (let* ((package-license-set-ids
             (log-time "fetching inferior package license metadata"
                       (lambda ()
                         (inferior-packages->license-set-ids conn inf
@@ -210,7 +218,16 @@
             (log-time "getting package-ids"
                       (lambda ()
                         (inferior-packages->package-ids
-                       conn packages packages-metadata-ids))))
+                         conn packages packages-metadata-ids)))))
+
+      (simple-format
+       #t "debug: finished loading information from inferior\n")
+      (close-inferior inf)
+
+      (let* ((derivation-ids
+              (derivation-file-names->derivation-ids
+               conn
+               (map fourth inferior-data-4-tuples)))
              (inferior-package-id->package-id-hash-table
               (alist->hashq-table
                (map (lambda (package package-id)
@@ -218,19 +235,6 @@
                             package-id))
                     packages
                     package-ids)))
-         (inferior-data-4-tuples
-          (log-time "getting inferior derivations"
-                    (lambda ()
-                      (all-inferior-package-derivations store inf packages)))))
-
-    (simple-format
-     #t "debug: finished loading information from inferior\n")
-    (close-inferior inf)
-
-    (let ((derivation-ids
-           (derivation-file-names->derivation-ids
-            conn
-            (map fourth inferior-data-4-tuples)))
              (flat-package-ids-systems-and-targets
               (map
                (match-lambda
@@ -239,11 +243,15 @@
                                    inferior-package-id)
                         system
                         target)))
-            inferior-data-4-tuples)))
+               inferior-data-4-tuples))
-
+             (package-derivation-ids
               (insert-package-derivations conn
                                           flat-package-ids-systems-and-targets
-                                  derivation-ids))))
+                                          derivation-ids)))
+
+        (record-end-time loading-inferior-data)
+
+        package-derivation-ids))))
 
 (define (inferior-package-transitive-supported-systems package)
   ((@@ (guix inferior) inferior-package-field)