The H-Store project is releasing the latest version of their experimental OLTP DBMS. This latest release mostly consists of stability and transactional correctness fixes, as well as new support for internal profiling of various performance metrics.

Major highlights of this release:

1. Improved speculative execution of single-partition transactions. All transactions can be speculatively executed whenever a multi-partition is blocking waiting to be executed. Use the site.exec_speculative_execution configuration to enable. (r2137, r2145, r2192)
2. New TransactionEstimator can automatically determine whether a transaction is single-partition at runtime. Distributed transactions are executed with the minimum number of partitions. Alternatively, you can use site.exec_force_singlepartitioned to force all transactions to execute as single-partitioned, and any mistakes are automatically rolled back and restarted as multi-partitioned.
3. Fixed concurrency/synchronization issues in ProtoRpcChannel/Server and VoltProcedureListener for write available callbacks. (r2183, r2155). Fixed synchronization issues for MarkovPathEstimator and TransactionEstimator (r2198)
4. Can now configure output directories for HStoreSite, Dtxn.Coordinator, and Client log files.
5. All node.* configuration parameters have been renamed to site.*.
6. Fixed a race condition when the middle PlanFragment for three-way joins would not get queued up for all partitions at the same time. This would cause the Dtxn.Coordinator to halt. (r2127)
7. Reduced JUnit test time by allowing each test case in a single JVM invocation to reuse benchmark project jar files. (r2139)

The source code for this release can be download via anonymous SVN:

https://database.cs.brown.edu/svn/hstore/tags/release-2011-07

Note also that the supplemental resource files (e.g., sample workload trace logs) have been moved out of the source code repository into a separate external repository:

https://database.cs.brown.edu/svn/hstore-files/