Make FDW Geo download code DRY

app/models/geo/tracking_base.rb

 # This module is intended to centralize all database access to the secondary
-# tracking database for Geo. 
+# tracking database for Geo.
 module Geo
   class TrackingBase < ActiveRecord::Base
     self.abstract_class = true

app/workers/geo/file_download_dispatch_worker.rb

@@ -33,24 +33,40 @@ module Geo
         .pluck(:file_id, :file_type)
     end
 
+    def selective_sync
+      current_node.restricted_project_ids
+    end
+
     def find_lfs_object_ids
       # Selective project replication adds a wrinkle to FDW queries, so
       # we fallback to the legacy version for now.
-      if Gitlab::Geo.fdw? && !current_node.restricted_project_ids
-        fdw_find_lfs_object_ids
-      else
-        legacy_find_lfs_object_ids
-      end
+      relation =
+        if Gitlab::Geo.fdw? && !selective_sync
+          fdw_find_lfs_object_ids
+        else
+          legacy_find_lfs_object_ids
+        end
+
+      relation
+        .limit(db_retrieve_batch_size)
+        .pluck(:id)
+        .map { |id| [id, :lfs] }
     end
 
     def find_upload_object_ids
       # Selective project replication adds a wrinkle to FDW queries, so
       # we fallback to the legacy version for now.
-      if Gitlab::Geo.fdw? && !current_node.restricted_project_ids
-        fdw_find_upload_object_ids
-      else
-        legacy_find_upload_object_ids
-      end
+      relation =
+        if Gitlab::Geo.fdw? && !selective_sync
+          fdw_find_upload_object_ids
+        else
+          legacy_find_upload_object_ids
+        end
+
+      relation
+        .limit(db_retrieve_batch_size)
+        .pluck(:id, :uploader)
+        .map { |id, uploader| [id, uploader.sub(/Uploader\z/, '').underscore] }
     end
 
     def fdw_find_lfs_object_ids
@@ -60,10 +76,6 @@ module Geo
       Geo::Fdw::LfsObject.joins("LEFT OUTER JOIN file_registry ON file_registry.file_id = #{fdw_table}.id AND file_registry.file_type = 'lfs'")
         .where("#{fdw_table}.file_store IS NULL OR #{fdw_table}.file_store = #{LfsObjectUploader::LOCAL_STORE}")
         .where('file_registry.file_id IS NULL')
-        .order(created_at: :desc)
-        .limit(db_retrieve_batch_size)
-        .pluck(:id)
-        .map { |id| [id, :lfs] }
     end
 
     def fdw_find_upload_object_ids
@@ -73,35 +85,22 @@ module Geo
       Geo::Fdw::Upload.joins("LEFT OUTER JOIN file_registry ON file_registry.file_id = #{fdw_table}.id AND file_registry.file_type IN (#{obj_types})")
         .where('file_registry.file_id IS NULL')
         .order(created_at: :desc)
-        .limit(db_retrieve_batch_size)
-        .pluck(:id, :uploader)
-        .map { |id, uploader| [id, uploader.sub(/Uploader\z/, '').underscore] }
     end
 
     def legacy_find_upload_object_ids
-      unsynced_downloads = legacy_filter_registry_ids(
+      legacy_filter_registry_ids(
         current_node.uploads,
         Geo::FileService::DEFAULT_OBJECT_TYPES,
         Upload.table_name
       )
-
-      unsynced_downloads
-        .limit(db_retrieve_batch_size)
-        .pluck(:id, :uploader)
-        .map { |id, uploader| [id, uploader.sub(/Uploader\z/, '').underscore] }
     end
 
     def legacy_find_lfs_object_ids
-      unsynced_downloads = legacy_filter_registry_ids(
+      legacy_filter_registry_ids(
         current_node.lfs_objects,
         [:lfs],
         LfsObject.table_name
       )
-
-      unsynced_downloads
-        .limit(db_retrieve_batch_size)
-        .pluck(:id)
-        .map { |id| [id, :lfs] }
     end
 
     # This query requires data from two different databases, and unavoidably