If you want a free database, use PostgreSQL, the Windev connector for PostgreSQL is free to download and install on your windev as a replacement for HFSQL, it will be way more powerful while using the usual hFunctions like you would with HFSQL, plus you will find a ton of docs on the web to do powerful stuff.
HFSQL is in fact the same as an old ISAM DBASE database so it requires re-indexations and things like that of those older DB systems era.
PostgreSQL is like having a free Oracle DB with all the powerful features and reliability, we dropped HFSQL for this and performance has increased tenfold plus all the other benefits while keeping our code pretty much the same, every day feels like we discover freebies and gifts from ProsgreSQL since our migration :)
Free VS Free... You gotta go with power and sheer size of web documentation and poeple available to help .