Hi @seewhy,
For your specific scenario, I believe this should work, though maybe not for the reason you think. It also may take ~24 hrs for you to see the size reduction. This is what will happen under the hood when you DELETE a submission attachment via the API: the data will continue be stored in the database as a blob, but that blob will be unlinked from the submission attachment record. Then a daily cron job for purging deleted forms that have been in the trash for 30 days will do its work and also remove any unattached blobs, including the submission attachment blobs. You could also run that form purging script manually. Everything else should still function because Central is robust to missing submission attachments.
Just be aware that if you delete these attachments, even before they are purged from the database, it wont really be possible to get them back! So proceed with caution!
We are also actively working on ways to reduce storage size in Central, including:
- making it possible to store blobs outside of the database
- working on full submission deletion