Speed up deleting blocked_builds entries

guix-data-service/data-deletion.scm

@@ -388,14 +388,28 @@ DELETE FROM builds WHERE id IN ("
   (define (delete-blocked-builds-for-derivation-output-details-set
            conn
            derivation-output-details-set-id)
-    (exec-query
-     conn
-     "
+    ;; Do this for each build server individually, as that helps PostgreSQL
+    ;; efficiently check the partitions
+    (let ((build-server-ids
+           (map
+            car
+            (exec-query
+             conn
+             "SELECT id FROM build_servers"))))
+      (for-each
+       (lambda (build-server-id)
+         (exec-query
+          conn
+          "
 DELETE FROM blocked_builds
-WHERE blocked_derivation_output_details_set_id = $1
-   OR blocking_derivation_output_details_set_id = $2"
-     (list derivation-output-details-set-id
-           derivation-output-details-set-id)))
+WHERE build_server_id = $1
+  AND (
+    blocked_derivation_output_details_set_id = $2 OR blocking_derivation_output_details_set_id = $3
+  )"
+          (list build-server-id
+                derivation-output-details-set-id
+                derivation-output-details-set-id)))
+       build-server-ids)))
 
   (define (delete-unreferenced-derivations-source-files conn)
     (exec-query