The ink was still drying on Sun's billion-dollar deal to buy the webby, low-end open source database house MySQL when Sun turned around and put money in the high-end open source Postgres company Greenplum, evidently what Sun CEO Jonathan Schwartz meant last week when he said "and we ain't finished yet."

Schwartz did say that Sun would continue to invest in Postgres, Oracle and JavaDB last week when Sun's MySQL buy was announced. Looks like we should have taken him literally.

Greenplum also attracted SAP, which has no track record of open source investments, as another strategic investor - and SAP is fresh from closing its acquisition of Business Objects, the Franco-American BI concern.

Greenplum, of course, is an enterprise BI database - known for its massively parallel and shared nothing architecture - that Sun already uses in its Data Warehouse Appliance. It competes with Oracle, Teradata, HP and IBM.

According to Jonathan, "Greenplum's leverage of Postgres to disrupt the proprietary vendors with breakthrough business intelligence solutions creates opportunity for their investors, and more importantly, our mutual customers."

There is speculation it could push Sun into an open source SOA platform built around its Java Enterprise System and its SeeBeyond-derived widgetry, and into future competition with JBoss.

SAP said it invested because it's seeing "demand for scalable database technologies to support analytical and data-driven applications."

Greenplum's widgetry runs on Linux, well, at least Red Hat Linux, Solaris and OSX.

Sun and SAP came in on a $27 million C round led by Meritech Capital Partners, the late-stage VC that backed Facebook, Salesforce.com and Larry Ellison's newly public NetSuite.

Greenplum, which is now run by ex-Sun top sales exec Bill Cook, who also did a turn at Penguin Computers, has already been through $28.7 million (ignoring the $19.5 million raised before it became Greenplum). It's earmarked the new money for continued development and expanded sales and marketing. It wants to grow its share of the $20 billion database market.

Along with the investment, Greenplum said it has hired Paul Salazar, at one time senior director of marketing at SpikeSource and before that director of EMEA marketing at Red Hat, as VP of corporate marketing. It has also hired another Sun veteran, Joe Otto, as VP, worldwide sales.