15. The apparatus of claim 14 , wherein the program code is further configured such that mapping each operand in the plurality of operands into the operand map comprises assigning each operand in the plurality of operands to a separate bit in a binary operand map, and wherein the operand identifier for a node comprises a binary value that includes a bit set for each operand identified by the operand identifier according to the binary operand map.
14. An apparatus comprising: a processor; and program code configured to be executed by the processor to represent a database query expression for use during execution of the query expression by a computer, wherein the database query expression includes a plurality of predicates related to one another by at least one logical relation, the program code configured to generate a plurality of operands from the database query expression, wherein each operand in the plurality of operands is representative of a predicate in the plurality of predicates; the program code further configured to map each operand among the plurality of operands into an operand map; and the program code further configured to generate a hierarchical data structure based upon the generated plurality of operands, wherein the data structure includes a plurality of nodes, wherein each node includes an operand identifier that identifies at least one operand from the plurality of operands based upon the operand map, wherein each node defines a first logical relation between those predicates in the database query expression that are represented by operands identified by the operand identifier for such node, and wherein the plurality of nodes are arranged relative to one another in the data structure within multiple hierarchical levels to define at least a second logical relation among predicates in the database query expression.