  Over the past decade, we have witnessed a dramatic evolution in main-memory
capacity and multi-core parallelism of server hardware. To leverage this
hardware potential, multi-core in-memory OLTP database systems have been
extensively re-designed. The core objective of this re-design has been scaling
up sequential execution of OLTP transactions, wherein alternative database
architectures have been explored to eliminate system bottlenecks and overheads
impeding inter-transaction parallelism to fully manifest. However,
intra-transaction parallelism has been largely ignored by this previous work.
We conjecture this situation to have developed because OLTP workloads are
sometimes deemed to have far too little intra-transactional parallelism and,
even when this kind of parallelism is available, program analyses to recognize
it in arbitrary stored procedures are considered too brittle to be used as a
general tool. Recently, however, a new concept of actor-relational database
systems has been proposed, raising hopes that application developers can
specify intra-transaction parallelism by modeling database applications as
communicating actors. In this scenario, a natural question is whether an
actor-relational database system with an asynchronous programming model can
adequately expose the intra-transaction parallelism available in application
logic to modern multi-core hardware. Towards that aim, we conduct in this paper
an experimental evaluation of the factors that affect intra-transaction
parallelism in the prototype actor-relational database system REACTDB, with an
OLTP application designed with task-level parallelism in mind, and with the
system running on a multi-core machine.
