Support reindexing unique indexes

This enables >=PG12-compatible reindexing behavior leveraging
REINDEX CONCURRENTLY which supports reindexing unique indexes.

Changelog: other

config/feature_flags/development/database_reindexing_pg12.yml

----
-name: database_reindexing_pg12
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/64695
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/334372
-milestone: '14.1'
-type: development
-group: group::database
-default_enabled: false

doc/administration/raketasks/maintenance.md

@@ -348,7 +348,6 @@ sudo gitlab-rake gitlab:db:reindex['public.a_specific_index']
 
 The following index types are not supported:
 
-1. Unique and primary key indexes
 1. Indexes used for constraint exclusion
 1. Partitioned indexes
 1. Expression indexes

lib/gitlab/database/postgres_index.rb

@@ -18,19 +18,12 @@ module Gitlab
         find(identifier)
       end
 
-      # 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.
-      #
-      # Deprecated: Switch to scope .reindexing_support
-      scope :regular, -> { where(unique: false, partitioned: false, exclusion: false, expression: false, type: Gitlab::Database::Reindexing::SUPPORTED_TYPES)}
-
-      # Indexes for reindexing with PG12
+      # Indexes with reindexing support
       scope :reindexing_support, -> { where(partitioned: false, exclusion: false, expression: false, type: Gitlab::Database::Reindexing::SUPPORTED_TYPES) }
 
-      scope :not_match, ->(regex) { where("name !~ ?", regex)}
+      scope :not_match, ->(regex) { where("name !~ ?", regex) }
 
-      scope :match, ->(regex) { where("name ~* ?", regex)}
+      scope :match, ->(regex) { where("name ~* ?", regex) }
 
       scope :not_recently_reindexed, -> do
         recent_actions = Reindexing::ReindexAction.recent.where('index_identifier = identifier')

lib/gitlab/database/reindexing.rb

@@ -16,16 +16,9 @@ module Gitlab
       end
 
       def self.candidate_indexes
-        indexes = Gitlab::Database::PostgresIndex
-          .not_match("^#{ConcurrentReindex::TEMPORARY_INDEX_PREFIX}")
-          .not_match("^#{ConcurrentReindex::REPLACED_INDEX_PREFIX}")
+        Gitlab::Database::PostgresIndex
           .not_match("#{ReindexConcurrently::TEMPORARY_INDEX_PATTERN}$")
-
-        if Feature.enabled?(:database_reindexing_pg12, type: :development)
-          indexes.reindexing_support
-        else
-          indexes.regular
-        end
+          .reindexing_support
       end
     end
   end

lib/gitlab/database/reindexing/concurrent_reindex.rb

-# frozen_string_literal: true
-
-module Gitlab
-  module Database
-    module Reindexing
-      class ConcurrentReindex
-        include Gitlab::Utils::StrongMemoize
-
-        ReindexError = Class.new(StandardError)
-
-        PG_IDENTIFIER_LENGTH = 63
-        TEMPORARY_INDEX_PREFIX = 'tmp_reindex_'
-        REPLACED_INDEX_PREFIX = 'old_reindex_'
-        STATEMENT_TIMEOUT = 9.hours
-
-        # When dropping an index, we acquire a SHARE UPDATE EXCLUSIVE lock,
-        # which only conflicts with DDL and vacuum. We therefore execute this with a rather
-        # high lock timeout and a long pause in between retries. This is an alternative to
-        # setting a high statement timeout, which would lead to a long running query with effects
-        # on e.g. vacuum.
-        REMOVE_INDEX_RETRY_CONFIG = [[1.minute, 9.minutes]] * 30
-
-        attr_reader :index, :logger
-
-        def initialize(index, logger: Gitlab::AppLogger)
-          @index = index
-          @logger = logger
-        end
-
-        def perform
-          raise ReindexError, 'UNIQUE indexes are currently not supported' if index.unique?
-          raise ReindexError, 'partitioned indexes are currently not supported' if index.partitioned?
-          raise ReindexError, 'indexes serving an exclusion constraint are currently not supported' if index.exclusion?
-          raise ReindexError, 'index is a left-over temporary index from a previous reindexing run' if index.name.start_with?(TEMPORARY_INDEX_PREFIX, REPLACED_INDEX_PREFIX)
-
-          logger.info "Starting reindex of #{index}"
-
-          with_rebuilt_index do |replacement_index|
-            swap_index(replacement_index)
-          end
-        end
-
-        private
-
-        def with_rebuilt_index
-          if Gitlab::Database::PostgresIndex.find_by(schema: index.schema, name: replacement_index_name)
-            logger.debug("dropping dangling index from previous run (if it exists): #{replacement_index_name}")
-            remove_index(index.schema, replacement_index_name)
-          end
-
-          create_replacement_index_statement = index.definition
-            .sub(/CREATE INDEX #{index.name}/, "CREATE INDEX CONCURRENTLY #{replacement_index_name}")
-
-          logger.info("creating replacement index #{replacement_index_name}")
-          logger.debug("replacement index definition: #{create_replacement_index_statement}")
-
-          set_statement_timeout do
-            connection.execute(create_replacement_index_statement)
-          end
-
-          replacement_index = Gitlab::Database::PostgresIndex.find_by(schema: index.schema, name: replacement_index_name)
-
-          unless replacement_index.valid_index?
-            message = 'replacement index was created as INVALID'
-            logger.error("#{message}, cleaning up")
-            raise ReindexError, "failed to reindex #{index}: #{message}"
-          end
-
-          # Some expression indexes (aka functional indexes)
-          # require additional statistics. The existing statistics
-          # are tightly bound to the original index. We have to
-          # rebuild statistics for the new index before dropping
-          # the original one.
-          rebuild_statistics if index.expression?
-
-          yield replacement_index
-        ensure
-          begin
-            remove_index(index.schema, replacement_index_name)
-          rescue StandardError => e
-            logger.error(e)
-          end
-        end
-
-        def swap_index(replacement_index)
-          logger.info("swapping replacement index #{replacement_index} with #{index}")
-
-          with_lock_retries do
-            rename_index(index.schema, index.name, replaced_index_name)
-            rename_index(replacement_index.schema, replacement_index.name, index.name)
-            rename_index(index.schema, replaced_index_name, replacement_index.name)
-          end
-        end
-
-        def rename_index(schema, old_index_name, new_index_name)
-          connection.execute(<<~SQL)
-            ALTER INDEX #{quote_table_name(schema)}.#{quote_table_name(old_index_name)}
-            RENAME TO #{quote_table_name(new_index_name)}
-          SQL
-        end
-
-        def remove_index(schema, name)
-          logger.info("Removing index #{schema}.#{name}")
-
-          retries = Gitlab::Database::WithLockRetriesOutsideTransaction.new(
-            timing_configuration: REMOVE_INDEX_RETRY_CONFIG,
-            klass: self.class,
-            logger: logger
-          )
-
-          retries.run(raise_on_exhaustion: false) do
-            connection.execute(<<~SQL)
-              DROP INDEX CONCURRENTLY
-              IF EXISTS #{quote_table_name(schema)}.#{quote_table_name(name)}
-            SQL
-          end
-        end
-
-        def rebuild_statistics
-          logger.info("rebuilding table statistics for #{index.schema}.#{index.tablename}")
-
-          connection.execute(<<~SQL)
-            ANALYZE #{quote_table_name(index.schema)}.#{quote_table_name(index.tablename)}
-          SQL
-        end
-
-        def replacement_index_name
-          @replacement_index_name ||= "#{TEMPORARY_INDEX_PREFIX}#{index.indexrelid}"
-        end
-
-        def replaced_index_name
-          @replaced_index_name ||= "#{REPLACED_INDEX_PREFIX}#{index.indexrelid}"
-        end
-
-        def with_lock_retries(&block)
-          arguments = { klass: self.class, logger: logger }
-          Gitlab::Database::WithLockRetries.new(**arguments).run(raise_on_exhaustion: true, &block)
-        end
-
-        def set_statement_timeout
-          execute("SET statement_timeout TO '%ds'" % STATEMENT_TIMEOUT)
-          yield
-        ensure
-          execute('RESET statement_timeout')
-        end
-
-        delegate :execute, :quote_table_name, to: :connection
-        def connection
-          @connection ||= ActiveRecord::Base.connection
-        end
-      end
-    end
-  end
-end

lib/gitlab/database/reindexing/coordinator.rb

@@ -41,13 +41,7 @@ module Gitlab
         end
 
         def perform_for(index, action)
-          strategy = if Feature.enabled?(:database_reindexing_pg12, type: :development)
-                       ReindexConcurrently
-                     else
-                       ConcurrentReindex
-                     end
-
-          strategy.new(index).perform
+          ReindexConcurrently.new(index).perform
         rescue StandardError
           action.state = :failed
 

lib/tasks/gitlab/db.rake

@@ -154,7 +154,7 @@ namespace :gitlab do
       Rake::Task['gitlab:db:create_dynamic_partitions'].invoke
     end
 
-    desc 'reindex a regular (non-unique) index without downtime to eliminate bloat'
+    desc 'reindex a regular index without downtime to eliminate bloat'
     task :reindex, [:index_name] => :environment do |_, args|
       unless Feature.enabled?(:database_reindexing, type: :ops)
         puts "This feature (database_reindexing) is currently disabled.".color(:yellow)

spec/lib/gitlab/database/postgres_index_spec.rb

@@ -22,30 +22,6 @@ RSpec.describe Gitlab::Database::PostgresIndex do
 
   it_behaves_like 'a postgres model'
 
-  describe '.regular' do
-    it 'only non-unique indexes' do
-      expect(described_class.regular).to all(have_attributes(unique: false))
-    end
-
-    it 'only non partitioned indexes' do
-      expect(described_class.regular).to all(have_attributes(partitioned: false))
-    end
-
-    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
-
-    it 'only btree and gist indexes' do
-      types = described_class.regular.map(&:type).uniq
-
-      expect(types & %w(btree gist)).to eq(types)
-    end
-  end
-
   describe '.reindexing_support' do
     it 'only non partitioned indexes' do
       expect(described_class.reindexing_support).to all(have_attributes(partitioned: false))

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

@@ -11,7 +11,7 @@ RSpec.describe Gitlab::Database::Reindexing::Coordinator do
 
     let(:index) { create(:postgres_index) }
     let(:notifier) { instance_double(Gitlab::Database::Reindexing::GrafanaNotifier, notify_start: nil, notify_end: nil) }
-    let(:reindexer) { instance_double(Gitlab::Database::Reindexing::ConcurrentReindex, perform: nil) }
+    let(:reindexer) { instance_double(Gitlab::Database::Reindexing::ReindexConcurrently, perform: nil) }
     let(:action) { create(:reindex_action, index: index) }
 
     let!(:lease) { stub_exclusive_lease(lease_key, uuid, timeout: lease_timeout) }
@@ -19,7 +19,13 @@ RSpec.describe Gitlab::Database::Reindexing::Coordinator do
     let(:lease_timeout) { 1.day }
     let(:uuid) { 'uuid' }
 
-    shared_examples_for 'reindexing coordination' do
+    before do
+      swapout_view_for_table(:postgres_indexes)
+
+      allow(Gitlab::Database::Reindexing::ReindexConcurrently).to receive(:new).with(index).and_return(reindexer)
+      allow(Gitlab::Database::Reindexing::ReindexAction).to receive(:create_for).with(index).and_return(action)
+    end
+
     context 'locking' do
       it 'acquires a lock while reindexing' do
         expect(lease).to receive(:try_obtain).ordered.and_return(uuid)
@@ -33,7 +39,7 @@ RSpec.describe Gitlab::Database::Reindexing::Coordinator do
 
       it 'does not perform reindexing actions if lease is not granted' do
         expect(lease).to receive(:try_obtain).ordered.and_return(false)
-          expect(Gitlab::Database::Reindexing::ConcurrentReindex).not_to receive(:new)
+        expect(Gitlab::Database::Reindexing::ReindexConcurrently).not_to receive(:new)
 
         subject
       end
@@ -73,29 +79,4 @@ RSpec.describe Gitlab::Database::Reindexing::Coordinator do
       end
     end
   end
-
-    context 'legacy reindexing method (< PG12) - to be removed' do
-      before do
-        stub_feature_flags(database_reindexing_pg12: false)
-        swapout_view_for_table(:postgres_indexes)
-
-        allow(Gitlab::Database::Reindexing::ConcurrentReindex).to receive(:new).with(index).and_return(reindexer)
-        allow(Gitlab::Database::Reindexing::ReindexAction).to receive(:create_for).with(index).and_return(action)
-      end
-
-      it_behaves_like 'reindexing coordination'
-    end
-
-    context 'PG12 reindexing method' do
-      before do
-        stub_feature_flags(database_reindexing_pg12: true)
-        swapout_view_for_table(:postgres_indexes)
-
-        allow(Gitlab::Database::Reindexing::ReindexConcurrently).to receive(:new).with(index).and_return(reindexer)
-        allow(Gitlab::Database::Reindexing::ReindexAction).to receive(:create_for).with(index).and_return(action)
-      end
-
-      it_behaves_like 'reindexing coordination'
-    end
-  end
 end

spec/lib/gitlab/database/reindexing_spec.rb

@@ -29,30 +29,11 @@ RSpec.describe Gitlab::Database::Reindexing do
   describe '.candidate_indexes' do
     subject { described_class.candidate_indexes }
 
-    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]*$').with(no_args).and_return(result)
-
-        expect(subject).to eq(result)
-      end
-    end
-
-    context 'with deprecated method for >= PG12' do
-      before do
-        stub_feature_flags(database_reindexing_pg12: true)
-      end
-
     it 'retrieves regular indexes that are no left-overs from previous runs' do
       result = double
-        expect(Gitlab::Database::PostgresIndex).to receive_message_chain('not_match.not_match.not_match.reindexing_support').with('^tmp_reindex_').with('^old_reindex_').with('\_ccnew[0-9]*$').with(no_args).and_return(result)
+      expect(Gitlab::Database::PostgresIndex).to receive_message_chain('not_match.reindexing_support').with('\_ccnew[0-9]*$').with(no_args).and_return(result)
 
       expect(subject).to eq(result)
     end
   end
-  end
 end