Add user index on spam logs

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/327481

changelogs/unreleased/ab-spam-logs-index.yml

+---
+title: Add user index on spam logs
+merge_request: 59151
+author:
+type: performance

db/migrate/20210412142223_add_user_index_on_spam_logs.rb

+# frozen_string_literal: true
+
+class AddUserIndexOnSpamLogs < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  INDEX_NAME = 'index_spam_logs_on_user_id'
+
+  def up
+    add_concurrent_index :spam_logs, :user_id, name: INDEX_NAME
+  end
+
+  def down
+    remove_concurrent_index_by_name :spam_logs, INDEX_NAME
+  end
+end

db/schema_migrations/20210412142223

+4a1435a56b8e5cddd83b844f84374bca91810bbfc5f44faf2a53fd41f93be69c
\ No newline at end of file

db/structure.sql

@@ -23943,6 +23943,8 @@ CREATE UNIQUE INDEX index_sop_configs_on_project_id ON security_orchestration_po
 
 CREATE INDEX index_sop_configurations_project_id_policy_project_id ON security_orchestration_policy_configurations USING btree (security_policy_management_project_id, project_id);
 
+CREATE INDEX index_spam_logs_on_user_id ON spam_logs USING btree (user_id);
+
 CREATE INDEX index_sprints_iterations_cadence_id ON sprints USING btree (iterations_cadence_id);
 
 CREATE INDEX index_sprints_on_description_trigram ON sprints USING gin (description gin_trgm_ops);