Abstract: Various embodiments provide a data stream processing method. The method may include receiving by at least one first processor a data stream comprising first data that includes transactions to be executed on a database, receiving by at least one second processor from the at least one first processor information regarding data access to the database and second data indicative of a time-based order of the transactions, the information extracted from the first data and the second data, receiving by at least one third processor from the at least one first processor the first data, and processing the transactions by the at least one third processor, wherein the at least one second processor provides data access to the database to the at least one third processor based on the time-based order determined from the second data.

Abstract: A method for predictable query execution through early materialization is provided. The method deals with the problem of cardinality misestimation in query execution plans, by pre-executing sub-plans on a query execution plan that have questionable estimates and collecting statistics on the output of these sub-plans. If needed, the overall query execution plan is changed in light of these statistics, before optimizing and executing the remainder of the query.

Abstract: A way for progressively refining a query execution plan during query execution in a federated data system is provided. Re-optimization constraints are placed in the query execution plan during query compilation. When a re-optimization constraint is violated during query execution, a model of the query execution plan is refined using a partially executed query to form a new query execution plan. The new query execution plan is compiled. The compiled new query execution plan is executed.

Abstract: A method and system for method for accelerating execution of a query on a federated database system is disclosed. The federated database system is associated with an external data source, which is used by the query. The query is performed based upon a query execution plan. The method and system include generating an optimizer query for the external data source utilized by the query. The optimizer query is based on the query and obtains data related to the external data source. The method and system further include providing the optimizer query to the external data source and collecting at least one resultant from the optimizer query for use in generating a future query execution plan.