Remove redundant index on creator_id and created_at from projects

changelogs/unreleased/213800-remove-redundant-index-from-projects.yml

+---
+title: Remove redundant index from projects table
+merge_request: 29507
+author:
+type: performance

db/migrate/20200414144547_remove_index_projects_on_creator_id_and_created_at_from_projects.rb

+# frozen_string_literal: true
+
+class RemoveIndexProjectsOnCreatorIdAndCreatedAtFromProjects < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  INDEX_NAME = 'index_projects_on_creator_id_and_created_at'
+
+  disable_ddl_transaction!
+
+  def up
+    remove_concurrent_index_by_name :projects, INDEX_NAME
+  end
+
+  def down
+    add_concurrent_index :projects, [:creator_id, :created_at], name: INDEX_NAME
+  end
+end

db/structure.sql

@@ -9927,8 +9927,6 @@ CREATE INDEX index_projects_api_vis20_updated_at ON public.projects USING btree
 
 CREATE INDEX index_projects_on_created_at_and_id ON public.projects USING btree (created_at, id);
 
-CREATE INDEX index_projects_on_creator_id_and_created_at ON public.projects USING btree (creator_id, created_at);
-
 CREATE INDEX index_projects_on_creator_id_and_created_at_and_id ON public.projects USING btree (creator_id, created_at, id);
 
 CREATE INDEX index_projects_on_creator_id_and_id ON public.projects USING btree (creator_id, id);
@@ -13178,6 +13176,7 @@ COPY "schema_migrations" (version) FROM STDIN;
 20200408175424
 20200409211607
 20200410232012
+20200414144547
 20200415160722
 20200415161021
 20200415161206