Remove redundant index on epics

changelogs/unreleased/remove_epics_index.yml

+---
+title: Remove redundant index from epics
+merge_request: 59494
+author:
+type: other

db/migrate/20210415144538_remove_index_epics_on_group_id_from_epics.rb

+# frozen_string_literal: true
+
+class RemoveIndexEpicsOnGroupIdFromEpics < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  INDEX_NAME = 'index_epics_on_group_id'
+
+  disable_ddl_transaction!
+
+  def up
+    remove_concurrent_index_by_name :epics, INDEX_NAME
+  end
+
+  def down
+    add_concurrent_index :epics, :group_id, name: INDEX_NAME
+  end
+end

db/schema_migrations/20210415144538

+d237690af576fb5a85d984416dcca1936a140a10a9b6c968d3ff57419568fb8f
\ No newline at end of file

db/structure.sql

@@ -22603,8 +22603,6 @@ CREATE INDEX index_epics_on_due_date_sourcing_milestone_id ON epics USING btree
 
 CREATE INDEX index_epics_on_end_date ON epics USING btree (end_date);
 
-CREATE INDEX index_epics_on_group_id ON epics USING btree (group_id);
-
 CREATE UNIQUE INDEX index_epics_on_group_id_and_external_key ON epics USING btree (group_id, external_key) WHERE (external_key IS NOT NULL);
 
 CREATE UNIQUE INDEX index_epics_on_group_id_and_iid ON epics USING btree (group_id, iid);