Model: Improve performance of with_version_count scope

Changelog: performance

app/models/ml/model.rb

@@ -30,9 +30,12 @@ class Model < ApplicationRecord
     scope :including_latest_version, -> { includes(:latest_version) }
     scope :including_project, -> { includes(:project) }
     scope :with_version_count, -> {
-      left_outer_joins(:versions)
-        .select("ml_models.*, count(ml_model_versions.id) as version_count")
-        .group(:id)
+      version_counts = Ml::ModelVersion
+                         .select(:model_id, 'COUNT(*) as count')
+                         .group(:model_id)
+
+      joins("LEFT OUTER JOIN (#{version_counts.to_sql}) as version_counts ON version_counts.model_id = ml_models.id")
+        .select('ml_models.*, COALESCE(version_counts.count, 0) as version_count')
     }
     scope :by_name, ->(name) { where("ml_models.name LIKE ?", "%#{sanitize_sql_like(name)}%") } # rubocop:disable GitlabSecurity/SqlInjection
     scope :by_project, ->(project) { where(project_id: project.id) }