Fix EnvironmentSerializer preloads unrelated pipelines/builds

This commit fixes the problem that the serializer currently preloads
unrelated assocaited pipelines/builds of deployments.

app/models/environment.rb

@@ -24,13 +24,13 @@ class Environment < ApplicationRecord
   has_many :self_managed_prometheus_alert_events, inverse_of: :environment
   has_many :alert_management_alerts, class_name: 'AlertManagement::Alert', inverse_of: :environment
-  has_one :last_deployment, -> { success.order('deployments.id DESC') }, class_name: 'Deployment', inverse_of: :environment
+  has_one :last_deployment, -> { success.distinct_on_environment }, class_name: 'Deployment', inverse_of: :environment
   has_one :last_deployable, through: :last_deployment, source: 'deployable', source_type: 'CommitStatus'
   has_one :last_pipeline, through: :last_deployable, source: 'pipeline'
   has_one :last_visible_deployment, -> { visible.distinct_on_environment }, inverse_of: :environment, class_name: 'Deployment'
   has_one :last_visible_deployable, through: :last_visible_deployment, source: 'deployable', source_type: 'CommitStatus'
   has_one :last_visible_pipeline, through: :last_visible_deployable, source: 'pipeline'
-  has_one :upcoming_deployment, -> { running.order('deployments.id DESC') }, class_name: 'Deployment', inverse_of: :environment
+  has_one :upcoming_deployment, -> { running.distinct_on_environment }, class_name: 'Deployment', inverse_of: :environment
   has_one :latest_opened_most_severe_alert, -> { order_severity_with_open_prometheus_alert }, class_name: 'AlertManagement::Alert', inverse_of: :environment
   before_validation :nullify_external_url

changelogs/unreleased/fix-environment-ar-relationship-cause-massive-preloading.yml

+---
+title: Fix EnvironmentSerializer preloads unrelated pipelines/builds
+merge_request: 60562
+author:
+type: fixed