Bug 1559114 - Optimize signature verification of Remote Settings dump…

…s r=glasserc

Differential Revision: https://phabricator.services.mozilla.com/D34879

--HG--
extra : moz-landing-system : lando

services/settings/RemoteSettingsClient.jsm

@@ -316,7 +316,7 @@ class RemoteSettingsClient extends EventEmitter {
           // The worker only returns an integer. List the imported records to build the sync event.
           if (imported > 0) {
             console.debug(`${this.identifier} ${imported} records loaded from JSON dump`);
-            ({ data: importedFromDump } = await kintoCollection.list());
+            ({ data: importedFromDump } = await kintoCollection.list({ order: "" }));
           }
           collectionLastModified = await kintoCollection.db.getLastModified();
         } catch (e) {
@@ -333,7 +333,11 @@ class RemoteSettingsClient extends EventEmitter {
         // we fetch them and validate the signature immediately.
         if (this.verifySignature && ObjectUtils.isEmpty(await kintoCollection.metadata())) {
           console.debug(`${this.identifier} verify signature of local data`);
-          const { data: allData } = await kintoCollection.list({ order: "" });
+          let allData = importedFromDump;
+          if (importedFromDump.length == 0) {
+            // If dump was imported at some other point (eg. `.get()`), list local DB.
+            ({ data: allData } = await kintoCollection.list({ order: "" }));
+          }
           const localRecords = allData.map(r => kintoCollection.cleanLocalFields(r));
           const metadata = await kintoCollection.pullMetadata(this.httpClient());
           if (this.verifySignature) {