1. A database management system comprising: a) a network interface, for receiving database queries from two or more client applications, the client applications operating on two or more user client computers, the system providing a least one connection into the system for each such client application; b) a group of one or more operational nodes for executing the queries as database operations, each operational node implemented as a logical collection of software components that execute on one or more physical machines; c) multiple client applications establish connections with the database and interact with the system via queries in a query language; d) the queries are classified into different types including one or more of INSERT, SELECT, UPDATE, or Data Definition Language (DDL); e) a Dynamic Query Planner (DQP) analyzes queries received for execution from client applications and transforms those queries into Query Execution Steps (QES) based on Query Rewrite Rules (QRRs) which are dynamically specified to the system; f) a Query Execution Engine (QEE) executes the QES and produces the results of the queries that are then returned to the client that originated the queries; and g) a persistent state is associated with each connection.