Solution : https://service.sap.com/sap/support/notes/816056 (SAP Service marketplace login required)
Key words : 
influence explicit decisions made, vbuk~spe index, full table scan, database-specific notes, vbuk table, terms vbuk, database optimizer, database systems, long runtimes, select documents
Related Notes : 
       
| 768619 | Performance problems in Transaction V23 | 
| 129385 | Database hints in Open SQL |