HSQLDB binary format import

Tender approved in the budget by the TDF board


In order to remove the legacy Java / HSQLDB database completely, and move fully to Firebird in LibreOffice 5.4 it is necessary to be able to import old document data with high fidelity from the HSQLDB binary file format which we have used (for performance) inside so many of our existing ODB files. This task involves reading the existing (reasonably simple) Java serialization code, and writing an (import only) filter to import this data safely into base.