1 files changed, 71 insertions, 0 deletions
diff --git a/db/post_migrate/20220124130028_dedup_runner_projects.rb b/db/post_migrate/20220124130028_dedup_runner_projects.rb
new file mode 100644
index 00000000000..1a4c895f1c4
--- /dev/null
+++ b/db/post_migrate/20220124130028_dedup_runner_projects.rb
@@ -0,0 +1,71 @@
+# frozen_string_literal: true
+
+class DedupRunnerProjects < Gitlab::Database::Migration[1.0]
+  TABLE_NAME = :ci_runner_projects
+  TMP_INDEX_NAME = 'tmp_unique_ci_runner_projects_by_runner_id_and_project_id'
+  OLD_INDEX_NAME = 'index_ci_runner_projects_on_runner_id_and_project_id'
+  INDEX_NAME = 'index_unique_ci_runner_projects_on_runner_id_and_project_id'
+  BATCH_SIZE = 5000
+
+  disable_ddl_transaction!
+
+  module Ci
+    class RunnerProject < ActiveRecord::Base
+      include EachBatch
+
+      self.table_name = 'ci_runner_projects'
+    end
+  end
+
+  def up
+    last_runner_project_record_id = Ci::RunnerProject.maximum(:id) || 0
+
+    # This index will disallow further duplicates while we're deduplicating the data.
+    add_concurrent_index(TABLE_NAME, [:runner_id, :project_id], where: "id > #{Integer(last_runner_project_record_id)}", unique: true, name: TMP_INDEX_NAME)
+
+    Ci::RunnerProject.each_batch(of: BATCH_SIZE) do |relation|
+      duplicated_runner_projects = Ci::RunnerProject
+        .select('COUNT(*)', :runner_id, :project_id)
+        .where('(runner_id, project_id) IN (?)', relation.select(:runner_id, :project_id))
+        .group(:runner_id, :project_id)
+        .having('COUNT(*) > 1')
+
+      duplicated_runner_projects.each do |runner_project|
+        deduplicate_item(runner_project)
+      end
+    end
+
+    add_concurrent_index(TABLE_NAME, [:runner_id, :project_id], unique: true, name: INDEX_NAME)
+    remove_concurrent_index_by_name(TABLE_NAME, TMP_INDEX_NAME)
+    remove_concurrent_index_by_name(TABLE_NAME, OLD_INDEX_NAME)
+  end
+
+  def down
+    add_concurrent_index(TABLE_NAME, [:runner_id, :project_id], name: OLD_INDEX_NAME)
+    remove_concurrent_index_by_name(TABLE_NAME, TMP_INDEX_NAME)
+    remove_concurrent_index_by_name(TABLE_NAME, INDEX_NAME)
+  end
+
+  private
+
+  def deduplicate_item(runner_project)
+    runner_projects_records = Ci::RunnerProject
+      .where(project_id: runner_project.project_id, runner_id: runner_project.runner_id)
+      .order(updated_at: :asc)
+      .to_a
+
+    attributes = {}
+    runner_projects_records.each do |runner_projects_record|
+      params = runner_projects_record.attributes.except('id')
+      attributes.merge!(params.compact)
+    end
+
+    ApplicationRecord.transaction do
+      record_to_keep = runner_projects_records.pop
+      records_to_delete = runner_projects_records
+
+      Ci::RunnerProject.where(id: records_to_delete.map(&:id)).delete_all
+      record_to_keep.update!(attributes)
+    end
+  end
+end