Database System with Methodology for Parallel Schedule Generation in a Query Optimizer

A system for parallel optimization of a database query, the system comprising:

• a search engine for generating a plurality of parallel plans which can be used for obtaining data requested by the query, the parallel plans including parallel operators for executing portions of the query in parallel;
• a parallel scheduler for adjusting parallel operators of each parallel plan if necessary based on resources available for executing the query and creating a schedule for the parallel plan indicating a sequence for execution of operators of the parallel plan;
• and
• a module for determining execution cost of each parallel plan based on its schedule and selecting a particular parallel plan having lowest execution cost for obtaining data requested by the query.

A method for parallel optimization of a query requesting data from a database, the method comprising:

• creating a plurality of operator trees for executing the query, the operator trees providing for execution of portions of the query in parallel;
• adjusting the portions of the query to be executed in parallel based on memory resources available for executing the query;
• generating a schedule for execution of each operator tree;
• and
• selecting the operator tree having lowest execution cost based on its schedule for executing the query.