Migration for fixing missing traversal ids

This change fixes missing traversal ids for namespaces records. The
migration adds two temporary indexes to speed up the scheduling queries.

Changelog: added

db/post_migrate/20210611080951_fix_missing_traversal_ids.rb

+# frozen_string_literal: true
+
+class FixMissingTraversalIds < ActiveRecord::Migration[6.1]
+  include Gitlab::Database::MigrationHelpers
+
+  ROOTS_MIGRATION = 'BackfillNamespaceTraversalIdsRoots'
+  CHILDREN_MIGRATION = 'BackfillNamespaceTraversalIdsChildren'
+  DOWNTIME = false
+  BATCH_SIZE = 1_000
+  SUB_BATCH_SIZE = 50
+  DELAY_INTERVAL = 2.minutes
+  ROOT_NS_INDEX_NAME = 'tmp_index_namespaces_empty_traversal_ids_with_root_namespaces'
+  CHILD_INDEX_NAME = 'tmp_index_namespaces_empty_traversal_ids_with_child_namespaces'
+
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_index :namespaces, :id, where: "parent_id IS NULL AND traversal_ids = '{}'", name: ROOT_NS_INDEX_NAME
+    add_concurrent_index :namespaces, :id, where: "parent_id IS NOT NULL AND traversal_ids = '{}'", name: CHILD_INDEX_NAME
+
+    # Personal namespaces and top-level groups
+    final_delay = queue_background_migration_jobs_by_range_at_intervals(
+      ::Gitlab::BackgroundMigration::BackfillNamespaceTraversalIdsRoots::Namespace.base_query.where("traversal_ids = '{}'"),
+       ROOTS_MIGRATION,
+       DELAY_INTERVAL,
+       batch_size: BATCH_SIZE,
+       other_job_arguments: [SUB_BATCH_SIZE],
+       track_jobs: true
+    )
+    final_delay += DELAY_INTERVAL
+
+    # Subgroups
+    queue_background_migration_jobs_by_range_at_intervals(
+      ::Gitlab::BackgroundMigration::BackfillNamespaceTraversalIdsChildren::Namespace.base_query.where("traversal_ids = '{}'"),
+       CHILDREN_MIGRATION,
+       DELAY_INTERVAL,
+       batch_size: BATCH_SIZE,
+       initial_delay: final_delay,
+       other_job_arguments: [SUB_BATCH_SIZE],
+       track_jobs: true
+    )
+  end
+
+  def down
+    remove_concurrent_index_by_name :namespaces, ROOT_NS_INDEX_NAME
+    remove_concurrent_index_by_name :namespaces, CHILD_INDEX_NAME
+  end
+end

db/schema_migrations/20210611080951

+95e4b697f5c5b18935b73bbeb0c42c96e3e5abde9e4f9e179d1a93a891a0694b
\ No newline at end of file

db/structure.sql

@@ -25060,6 +25060,10 @@ CREATE INDEX tmp_idx_deduplicate_vulnerability_occurrences ON vulnerability_occu
 
 CREATE INDEX tmp_idx_on_namespaces_delayed_project_removal ON namespaces USING btree (id) WHERE (delayed_project_removal = true);
 
+CREATE INDEX tmp_index_namespaces_empty_traversal_ids_with_child_namespaces ON namespaces USING btree (id) WHERE ((parent_id IS NOT NULL) AND (traversal_ids = '{}'::integer[]));
+
+CREATE INDEX tmp_index_namespaces_empty_traversal_ids_with_root_namespaces ON namespaces USING btree (id) WHERE ((parent_id IS NULL) AND (traversal_ids = '{}'::integer[]));
+
 CREATE INDEX tmp_index_on_vulnerabilities_non_dismissed ON vulnerabilities USING btree (id) WHERE (state <> 2);
 
 CREATE UNIQUE INDEX uniq_pkgs_deb_grp_architectures_on_distribution_id_and_name ON packages_debian_group_architectures USING btree (distribution_id, name);