Relational support for flexible schema scenarios

Efficient support for applications that deal with data heterogeneity, hierarchies and schema evolution is an important challenge for relational engines. In this paper we show how this flexibility can be handled in Microsoft SQL Server. For this purpose, the engine has been equipped in an integrated package of relational extensions. The package includes sparse storage, column set operations, filtered indices, filtered statistics and hierarchy querying with OrdPath labeling. In addition, economical loading of metadata allow us to answer queries independently of the number of columns in a table and drastically improve scaling capabilities. The design of a prototypical content and collaboration application based on a wide table is described, along with experiments validating its performance.