I am pleased to (pre) announce the HSQLDB 1.9.x series, featuring
Multiversion Concurrency Control.
In this series, all rows involved in transactions include the full change
history. This allows multi-threaded, non-blocking reads and writes, with
conflict detection on commit.
The new architecture allows two new transaction isolation modes: Snapshot
Isolation and Read Consistency Isolation, which are respectively and
approximately equivalent to Repeatable Reads and Read Committed isolation
levels. Read Uncommitted will continue to be supported.
The first alpha release of the new series will be available from the file
download page by the end of the week.