The Force.com Multitenant Architecture: Understanding the Design of Salesforce.com’s Internet Application Development Platform

Internal Query Optimizations

Most modern database systems determine optimal query execution plans by employing a cost-based query optimizer that considers relevant statistics about target table and index data. However, conventional cost-based optimizer statistics are designed for single-tenant applications and fail to account for the data access characteristics of any given user executing a query in a multitenant environment. For example, a given query that targets an object (table) with a large volume of data would most likely execute more efficiently using different execution plans for users with high visibility (a manager that can see all object instances) versus users with low visibility (sales people that can only see rows related to themselves). ...