Support unique indexes for reindexing (PG12)

With feature flag :database_reindexing_pg12 set,
we now also consider unique indexes for reindexing.

lib/gitlab/database/postgres_index.rb

@@ -20,7 +20,12 @@ module Gitlab
       # A 'regular' index is a non-unique index,
       # that does not serve an exclusion constraint and
       # is defined on a table that is not partitioned.
-      scope :regular, -> { where(unique: false, partitioned: false, exclusion: false)}
+      #
+      # Deprecated: Switch to scope .reindexing_support
+      scope :regular, -> { where(unique: false, partitioned: false, exclusion: false, expression: false)}
+
+      # Indexes for reindexing with PG12
+      scope :reindexing_support, -> { where(partitioned: false, exclusion: false, expression: false) }
 
       scope :not_match, ->(regex) { where("name !~ ?", regex)}
 

lib/gitlab/database/reindexing.rb

@@ -14,12 +14,16 @@ module Gitlab
       end
 
       def self.candidate_indexes
-        Gitlab::Database::PostgresIndex
-          .regular
-          .where('NOT expression')
+        indexes = Gitlab::Database::PostgresIndex
           .not_match("^#{ConcurrentReindex::TEMPORARY_INDEX_PREFIX}")
           .not_match("^#{ConcurrentReindex::REPLACED_INDEX_PREFIX}")
           .not_match("#{ReindexConcurrently::TEMPORARY_INDEX_PATTERN}$")
+
+        if Feature.enabled?(:database_reindexing_pg12, type: :development)
+          indexes.reindexing_support
+        else
+          indexes.regular
+        end
       end
     end
   end

spec/lib/gitlab/database/postgres_index_spec.rb

@@ -34,6 +34,24 @@ RSpec.describe Gitlab::Database::PostgresIndex do
     it 'only indexes that dont serve an exclusion constraint' do
       expect(described_class.regular).to all(have_attributes(exclusion: false))
     end
+
+    it 'only non-expression indexes' do
+      expect(described_class.regular).to all(have_attributes(expression: false))
+    end
+  end
+
+  describe '.reindexing_support' do
+    it 'only non partitioned indexes' do
+      expect(described_class.reindexing_support).to all(have_attributes(partitioned: false))
+    end
+
+    it 'only indexes that dont serve an exclusion constraint' do
+      expect(described_class.reindexing_support).to all(have_attributes(exclusion: false))
+    end
+
+    it 'only non-expression indexes' do
+      expect(described_class.reindexing_support).to all(have_attributes(expression: false))
+    end
   end
 
   describe '.not_match' do

spec/lib/gitlab/database/reindexing_spec.rb

@@ -29,11 +29,30 @@ RSpec.describe Gitlab::Database::Reindexing do
   describe '.candidate_indexes' do
     subject { described_class.candidate_indexes }
 
-    it 'retrieves regular indexes that are no left-overs from previous runs' do
-      result = double
-      expect(Gitlab::Database::PostgresIndex).to receive_message_chain('regular.where.not_match.not_match.not_match').with(no_args).with('NOT expression').with('^tmp_reindex_').with('^old_reindex_').with('\_ccnew[0-9]*$').and_return(result)
+    context 'with deprecated method for < PG12' do
+      before do
+        stub_feature_flags(database_reindexing_pg12: false)
+      end
+
+      it 'retrieves regular indexes that are no left-overs from previous runs' do
+        result = double
+        expect(Gitlab::Database::PostgresIndex).to receive_message_chain('not_match.not_match.not_match.regular').with('^tmp_reindex_').with('^old_reindex_').with('\_ccnew[0-9]*$').with(no_args).and_return(result)
+
+        expect(subject).to eq(result)
+      end
+    end
 
-      expect(subject).to eq(result)
+    context 'with deprecated method for >= PG12' do
+      before do
+        stub_feature_flags(database_reindexing_pg12: true)
+      end
+
+      it 'retrieves regular indexes that are no left-overs from previous runs' do
+        result = double
+        expect(Gitlab::Database::PostgresIndex).to receive_message_chain('not_match.not_match.not_match.reindexing_support').with('^tmp_reindex_').with('^old_reindex_').with('\_ccnew[0-9]*$').with(no_args).and_return(result)
+
+        expect(subject).to eq(result)
+      end
     end
   end
 end