Add a limit of LFS oids to be linked at once

This limits the number of object ids that would be linked at once. We
only noticed a problem before with 30_000 oids, this limit is well
beyond that and with the updated queries we should be able to handle
that.

app/services/projects/lfs_pointers/lfs_link_service.rb

@@ -4,6 +4,9 @@
 module Projects
   module LfsPointers
     class LfsLinkService < BaseService
+      TooManyOidsError = Class.new(StandardError)
+
+      MAX_OIDS = 100_000
       BATCH_SIZE = 1000
 
       # Accept an array of oids to link
@@ -12,6 +15,10 @@ module Projects
       def execute(oids)
         return [] unless project&.lfs_enabled?
 
+        if oids.size > MAX_OIDS
+          raise TooManyOidsError, 'Too many LFS object ids to link, please push them manually'
+        end
+
         # Search and link existing LFS Object
         link_existing_lfs_objects(oids)
       end

changelogs/unreleased/35749-improve-performance-of-lfs_object-queries.yml

+---
+title: Improve performance of linking LFS objects during import
+merge_request: 19709
+author:
+type: performance

spec/services/projects/lfs_pointers/lfs_link_service_spec.rb

@@ -16,6 +16,13 @@ describe Projects::LfsPointers::LfsLinkService do
   end
 
   describe '#execute' do
+    it 'raises an error when trying to link too many objects at once' do
+      oids = Array.new(described_class::MAX_OIDS) { |i| "oid-#{i}" }
+      oids << 'the straw'
+
+      expect { subject.execute(oids) }.to raise_error(described_class::TooManyOidsError)
+    end
+
     it 'links existing lfs objects to the project' do
       expect(project.all_lfs_objects.count).to eq 2