Batch completion: delete the tracking row by key (2/3)

app/models/solid_queue/batch_execution.rb

@@ -24,6 +24,21 @@ def create_all_from_jobs(jobs)
         end
       end
 
+      # Shared by the tracking row's own destroy callback and by a finishing
+      # job, which deletes its row by key and checks from its own after_commit.
+      def finish_batch_for(batch_id)
+        # Every finishing job asks whether it was the last one, and almost never
+        # is. Asking the cheap question first means the batch row is only read
+        # for the job that actually finishes the batch. #finish asks it again, so
+        # this decides nothing on its own.
+        return if where(batch_id: batch_id).exists?
+
+        # Skip the serialized callback and metadata columns on this hot path
+        if batch = Batch.select(:id, :finished_at, :enqueued_at).find_by(id: batch_id)
+          batch.finish
+        end
+      end
+
       private
         def attempt_to_update_total_jobs(batch_id, jobs)
           new_jobs_count = count_new_jobs_among(jobs)
@@ -43,16 +58,7 @@ def count_new_jobs_among(jobs)
 
     private
       def finish_batch
-        # Every finishing job asks whether it was the last one, and almost never
-        # is. Asking the cheap question first means the batch row is only read
-        # for the job that actually finishes the batch. #finish asks it again, so
-        # this decides nothing on its own.
-        return if self.class.where(batch_id: batch_id).exists?
-
-        # Skip the serialized callback and metadata columns on this hot path
-        if batch = Batch.select(:id, :finished_at, :enqueued_at).find_by(id: batch_id)
-          batch.finish
-        end
+        self.class.finish_batch_for(batch_id)
       end
   end
 end

app/models/solid_queue/job/batchable.rb

@@ -11,6 +11,7 @@ module Batchable
 
         after_create :create_batch_execution, if: :batched?
         after_update :update_batch_progress, if: :batched?
+        after_commit :finish_batch_after_progress, on: :update
         before_destroy :destroy_batch_execution, if: :batched?
       end
 
@@ -31,10 +32,23 @@ def create_batch_execution
           BatchExecution.create_all_from_jobs([ self ])
         end
 
+        # The tracking row is deleted by key rather than loaded and destroyed:
+        # a finishing job already knows which row is its own. Completion is then
+        # checked from this job's own after_commit, which runs at the same point
+        # the tracking row's would have.
         def update_batch_progress
           return unless saved_change_to_finished_at? && finished_at.present?
 
-          batch_execution&.destroy!
+          @batch_execution_removed = BatchExecution.where(job_id: id).delete_all.positive?
+        rescue ActiveRecord::ActiveRecordError => e
+          SolidQueue.instrument(:batch_progress_error, batch_id: batch_id, job_id: id, error: e)
+        end
+
+        def finish_batch_after_progress
+          return unless @batch_execution_removed
+
+          @batch_execution_removed = false
+          BatchExecution.finish_batch_for(batch_id)
         rescue ActiveRecord::ActiveRecordError => e
           SolidQueue.instrument(:batch_progress_error, batch_id: batch_id, job_id: id, error: e)
         end