A comparison of flexible schemas for software as a service

A multi-tenant database system for Software as a Service (SaaS) should offer schemas that are flexible in that they can be extended for different versions of the application and dynamically modified while the system is on-line. This paper presents an experimental comparison of five techniques for implementing flexible schemas for SaaS. In three of these techniques, the database"owns"the schema in that its structure is explicitly defined in DDL. Included here is the commonly-used mapping where each tenant is given their own private tables, which we take as the baseline, and a mapping that employs Sparse Columns in Microsoft SQL Server. These techniques perform well, however they offer only limited support for schema evolution in the presence of existing data. Moreover they do not scale beyond a certain level. In the other two techniques, the application "owns" the schema in that it is mapped into generic structures in the database. Included here are XML in DB2 and P...

• Type: Conference
• Year: 2009
• Where: SIGMOD
• Authors: Stefan Aulbach, Dean Jacobs, Alfons Kemper, Michael Seibold
• Keywords: Database, Database"owns"the Schema, Flexible Schemas, Schema Evolution, SIGMOD 2009