New feature preview feature in LibreOffice 4.2 : Firebird SQL
connector for LibreOffice Base (Andrzej Hunt). When creating a new
Database, select Firebird Embedded in the drop down menu (you have to
first enable the Experimental features in Tools ▸Options ▸ LibreOffice
▸ Advanced). This allows creation of databases that performmany times
faster than the previous built-in HSQLDB 1.8, avoiding the C++-to-Java
overhead inherent in using HSQLDB. We plan to phase HSQLDB out over
the next few releases, and provide a smooth migration path to
Firebird.

https://www.libreoffice.org/download/4-2-new-features-and-fixes/