Files deleted during cron

Hi,

We noticed that our images where slowly being deleted every time cron ran. I think I finally found why and would like to have your opinion.

We started with a content type using a field field_content_image for a bundle called article. We later decided to move this to a field collection field_collec_content_image. We manually moved data in the database to migrate existing content and deleted the obsolete field_content_image field. But we failed to delete the obsolete content of the field_data_field_content_image table.

I tracked down our problem to field_cron() which calls field_purge_batch($limit); This function looks at the tables field_config_instance, field_config for field instances that have been deleted.
In our case, it found that field_content_image was a deleted field for the bundle article. It then proceeds to delete field's data. I haven't gone through all the code but highly suspect it ends up deleting the file both in the file_managed, file_usage table and file system.

The reason I filled this as a bug is because I would expect any file delete to use the function file_usage_delete which would have picked up that the file was still in use.

Can you confirm that the field_purge_data function is really responsible for deleting the files ? If so, why is this not checking file usage before delete ?

Thanks