PDF migration from an invoice tool

Hey there!

I’m creating a migration script from one system (doesn’t matter, but it is InvoiceNinja) to Dolibarr at the moment.

I use python to grep the relevant information from the old database and paste that to the Dolibarr database. I managed to migrate the customers, suppliers, supplier invoices and the customer invoices. In the old tool, you have the possibility to attach PDFs to supplier invoices, similar to Dolibarr. The files are copied via paramiko to the Dolibarr server.

The relevant database table is llx_ecm_files, but I have no clue, what the values of the columns ref and label represents, nor what the idea of the directories documents/fournisseur/facture/x/y/ is.

After uploading a file to a supplier invoice, I can find a change in llx_ecm_files, only.
INSERT INTO llx_ecm_files VALUES (94,'5ec6bf08a0cd43df5edf89b44418b379','37d32aac3355b50ef820a076532fe72e',NULL,1,'fournisseur/facture/8/0/RE2012-215','RE2012-215-sec-bigdata.jpg',NULL,NULL,'sec-bigdata.jpg','',NULL,NULL,1,'uploaded',NULL,'2021-01-05 21:54:02','2021-01-05 20:54:02',1,NULL,NULL);

The overall question is: The values seem to be MD5 hashes, but what is the input value? And what is the structure of the subdirectories, containing numbers between 0 and 9?