19. An article comprising a tangible computer-readable storage medium containing executable instructions stored thereon which, when executed, result in a processor performing: transforming an original query plan into an equivalent executable compact query plan comprising at least two source nodes including scan operations to source tables, the at least two source nodes coupled to at least one abstract node and at least one singleton node, wherein a child of the at least one abstract node comprises at least one of the source nodes or the at least one singleton node, but not another abstract node, wherein the at least one singleton node comprises a single operation selected from aggregate, union, order by, or null accepting full outer join, wherein the at least one abstract node comprises a set of operations selected from at least one of Cartesian product, evaluation, filter, left outer join, or null rejecting full outer join, and wherein the at least one abstract node is partitioned into multiple intra-partition commutable operations that can be executed in a different order from the original query plan based on upward compatibility or a combination of a single null rejecting left outer join operation and the multiple intra-partition commutable operations; computing maximal source sub-queries associated with the compact query plan; computing semi-join reductions of the maximal source sub-queries to provide an executable derivative query plan; and storing the derivative query plan on a machine readable device.
19. An article comprising a tangible computer-readable storage medium containing executable instructions stored thereon which, when executed, result in a processor performing: transforming an original query plan into an equivalent executable compact query plan comprising at least two source nodes including scan operations to source tables, the at least two source nodes coupled to at least one abstract node and at least one singleton node, wherein a child of the at least one abstract node comprises at least one of the source nodes or the at least one singleton node, but not another abstract node, wherein the at least one singleton node comprises a single operation selected from aggregate, union, order by, or null accepting full outer join, wherein the at least one abstract node comprises a set of operations selected from at least one of Cartesian product, evaluation, filter, left outer join, or null rejecting full outer join, and wherein the at least one abstract node is partitioned into multiple intra-partition commutable operations that can be executed in a different order from the original query plan based on upward compatibility or a combination of a single null rejecting left outer join operation and the multiple intra-partition commutable operations; computing maximal source sub-queries associated with the compact query plan; computing semi-join reductions of the maximal source sub-queries to provide an executable derivative query plan; and storing the derivative query plan on a machine readable device. 21. The article of claim 19 , containing executable instructions stored thereon which, when executed, result in the processor performing: revising one of the source nodes to include a bind join between a cache node and another node along a reduction path.