Update queue_batched_background_migration not to duplicate migrations

If migration with the same job class name, table name, column name, and
job arguments already exists do not create a new one, but rather log
warning and return.

Related to https://gitlab.com/gitlab-org/gitlab/-/issues/329511.

lib/gitlab/database/background_migration/batched_migration.rb

@@ -16,6 +16,10 @@ module Gitlab
 
         scope :queue_order, -> { order(id: :asc) }
         scope :queued, -> { where(status: [:active, :paused]) }
+        scope :for_configuration, ->(job_class_name, table_name, column_name, job_arguments) do
+          where(job_class_name: job_class_name, table_name: table_name, column_name: column_name)
+            .where("job_arguments = ?", job_arguments.to_json) # rubocop:disable Rails/WhereEquals
+        end
 
         enum status: {
           paused: 0,

lib/gitlab/database/migrations/background_migration_helpers.rb

@@ -137,6 +137,9 @@ module Gitlab
         # class must be present in the Gitlab::BackgroundMigration module, and the batch class (if specified) must be
         # present in the Gitlab::BackgroundMigration::BatchingStrategies module.
         #
+        # If migration with same job_class_name, table_name, column_name, and job_aruments already exists, this helper
+        # will log an warning and not create a new one.
+        #
         # job_class_name - The background migration job class as a string
         # batch_table_name - The name of the table the migration will batch over
         # batch_column_name - The name of the column the migration will batch over
@@ -180,6 +183,13 @@ module Gitlab
           sub_batch_size: SUB_BATCH_SIZE
         )
 
+          if Gitlab::Database::BackgroundMigration::BatchedMigration.for_configuration(job_class_name, batch_table_name, batch_column_name, job_arguments).exists?
+            Gitlab::AppLogger.warn "Batched background migration not enqueued because it already exists: " \
+              "job_class_name: #{job_class_name}, table_name: #{batch_table_name}, column_name: #{batch_column_name}, " \
+              "job_arguments: #{job_arguments.inspect}"
+            return
+          end
+
           job_interval = BATCH_MIN_DELAY if job_interval < BATCH_MIN_DELAY
 
           batch_max_value ||= connection.select_value(<<~SQL)
@@ -194,13 +204,13 @@ module Gitlab
             job_class_name: job_class_name,
             table_name: batch_table_name,
             column_name: batch_column_name,
+            job_arguments: job_arguments,
             interval: job_interval,
             min_value: batch_min_value,
             max_value: batch_max_value,
             batch_class_name: batch_class_name,
             batch_size: batch_size,
             sub_batch_size: sub_batch_size,
-            job_arguments: job_arguments,
             status: migration_status)
 
           # This guard is necessary since #total_tuple_count was only introduced schema-wise,

spec/lib/gitlab/database/background_migration/batched_migration_spec.rb

@@ -356,4 +356,29 @@ RSpec.describe Gitlab::Database::BackgroundMigration::BatchedMigration, type: :m
       subject
     end
   end
+
+  describe '.for_configuration' do
+    let!(:migration) do
+      create(
+        :batched_background_migration,
+        job_class_name: 'MyJobClass',
+        table_name: :projects,
+        column_name: :id,
+        job_arguments: [[:id], [:id_convert_to_bigint]]
+      )
+    end
+
+    before do
+      create(:batched_background_migration, job_class_name: 'OtherClass')
+      create(:batched_background_migration, table_name: 'other_table')
+      create(:batched_background_migration, column_name: 'other_column')
+      create(:batched_background_migration, job_arguments: %w[other arguments])
+    end
+
+    it 'finds the migration matching the given configuration parameters' do
+      actual = described_class.for_configuration('MyJobClass', :projects, :id, [[:id], [:id_convert_to_bigint]])
+
+      expect(actual).to contain_exactly(migration)
+    end
+  end
 end

spec/lib/gitlab/database/migrations/background_migration_helpers_spec.rb

@@ -269,6 +269,38 @@ RSpec.describe Gitlab::Database::Migrations::BackgroundMigrationHelpers do
       allow(Gitlab::Database::PgClass).to receive(:for_table).and_call_original
     end
 
+    context 'when such migration already exists' do
+      it 'does not create duplicate migration' do
+        create(
+          :batched_background_migration,
+          job_class_name: 'MyJobClass',
+          table_name: :projects,
+          column_name: :id,
+          interval: 10.minutes,
+          min_value: 5,
+          max_value: 1005,
+          batch_class_name: 'MyBatchClass',
+          batch_size: 200,
+          sub_batch_size: 20,
+          job_arguments: [[:id], [:id_convert_to_bigint]]
+        )
+
+        expect do
+          model.queue_batched_background_migration(
+            'MyJobClass',
+            :projects,
+            :id,
+            [:id], [:id_convert_to_bigint],
+            job_interval: 5.minutes,
+            batch_min_value: 5,
+            batch_max_value: 1000,
+            batch_class_name: 'MyBatchClass',
+            batch_size: 100,
+            sub_batch_size: 10)
+        end.not_to change { Gitlab::Database::BackgroundMigration::BatchedMigration.count }
+      end
+    end
+
     it 'creates the database record for the migration' do
       expect(Gitlab::Database::PgClass).to receive(:for_table).with(:projects).and_return(pgclass_info)