Add index to improve speed of vulnerabilities

Add index on (project_id, state, report_type, severity, id) to speed up
commonly executed queries.

Changelog: changed

db/post_migrate/20220316165539_add_index_to_vulnerabilities.rb

+# frozen_string_literal: true
+
+class AddIndexToVulnerabilities < Gitlab::Database::Migration[1.0]
+  INDEX_NAME = 'index_vulnerabilites_common_finder_query'
+
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_index(
+      :vulnerabilities,
+      %i[project_id state report_type severity id],
+      name: INDEX_NAME
+    )
+  end
+
+  def down
+    remove_concurrent_index_by_name(
+      :vulnerabilities,
+      INDEX_NAME
+    )
+  end
+end

db/schema_migrations/20220316165539

+beeab3a2197f11a40049e983a5184ab9b80370c9867461239e12a5ce36b8f5e8
\ No newline at end of file

db/structure.sql

@@ -29382,6 +29382,8 @@ CREATE UNIQUE INDEX index_vuln_historical_statistics_on_project_id_and_date ON v
 
 CREATE INDEX index_vuln_reads_on_project_id_state_severity_and_vuln_id ON vulnerability_reads USING btree (project_id, state, severity, vulnerability_id DESC);
 
+CREATE INDEX index_vulnerabilites_common_finder_query ON vulnerabilities USING btree (project_id, state, report_type, severity, id);
+
 CREATE INDEX index_vulnerabilities_on_author_id ON vulnerabilities USING btree (author_id);
 
 CREATE INDEX index_vulnerabilities_on_confirmed_by_id ON vulnerabilities USING btree (confirmed_by_id);

ee/spec/models/ee/vulnerability_spec.rb

@@ -29,7 +29,7 @@ RSpec.describe Vulnerability do
   let_it_be(:vulnerability) { create(:vulnerability, :sast, :confirmed, :low, project: project) }
   let_it_be(:finding) { create(:vulnerabilities_finding, vulnerability: vulnerability) }
 
-  it { is_expected.to have_locked_schema('1128736d19b1457375faecb3bf8017350431dbbca91222c8edfcfa7c649638fb').reference('https://gitlab.com/gitlab-org/gitlab/-/issues/349315') }
+  it { is_expected.to have_locked_schema('9dfcb7cb227f5880125b579d2848d78fbb82af0fa00eac00b0137c0da691bbc4').reference('https://gitlab.com/gitlab-org/gitlab/-/issues/349315') }
 
   describe 'enums' do
     it { is_expected.to define_enum_for(:state).with_values(state_values) }