Your opensource tools are going to be limited as most are designed for web performance testing. The commercial tools with long histories in the market all have support for database interfaces due to their market presence before the move from two tier client server with thick clients to three tier architectures with thin web clients.
That having been noted, I would encourage you to look at the three databases you note and find a common set of interfaces supported by all three, such as ODBC (note this is but one interface example, others exist which your research will show) Next, exercise your research skills to look at the tools which are available that are open source in nature to see which tools support your identified interfaces. Lastly, take a hard look at your tools and the skills on your team. Make sure you pick a tool that your team can effectively use, or it really would not matter if the tool was commercial or open source as the odds for success would be the same (and uniformly low).
Research skills and high levels of curiosity are prized skills for performance testers. As the guidance for finding a common interface shared by all three of your databases is as a first step on a path, let your curiosity and research lead you to the next set trail markers.