Remove upper index size limit for reindexing

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/345134

lib/gitlab/database/reindexing/index_selection.rb

@@ -9,8 +9,8 @@ module Gitlab
         # Only reindex indexes with a relative bloat level (bloat estimate / size) higher than this
         MINIMUM_RELATIVE_BLOAT = 0.2
 
-        # Only consider indexes with a total ondisk size in this range (before reindexing)
-        INDEX_SIZE_RANGE = (1.gigabyte..100.gigabyte).freeze
+        # Only consider indexes beyond this size (before reindexing)
+        INDEX_SIZE_MINIMUM = 1.gigabyte
 
         delegate :each, to: :indexes
 
@@ -32,7 +32,7 @@ module Gitlab
 
           @indexes ||= candidates
             .not_recently_reindexed
-            .where(ondisk_size_bytes: INDEX_SIZE_RANGE)
+            .where('ondisk_size_bytes >= ?', INDEX_SIZE_MINIMUM)
             .sort_by(&:relative_bloat_level) # forced N+1
             .reverse
             .select { |candidate| candidate.relative_bloat_level >= MINIMUM_RELATIVE_BLOAT }

spec/lib/gitlab/database/reindexing/index_selection_spec.rb

@@ -46,14 +46,14 @@ RSpec.describe Gitlab::Database::Reindexing::IndexSelection do
     expect(subject).not_to include(excluded.index)
   end
 
-  it 'excludes indexes larger than 100 GB ondisk size' do
-    excluded = create(
+  it 'includes indexes larger than 100 GB ondisk size' do
+    included = create(
       :postgres_index_bloat_estimate,
       index: create(:postgres_index, ondisk_size_bytes: 101.gigabytes),
       bloat_size_bytes: 25.gigabyte
     )
 
-    expect(subject).not_to include(excluded.index)
+    expect(subject).to include(included.index)
   end
 
   context 'with time frozen' do