1. A method comprising: compiling a decision tree data structure including a plurality of nodes using a classifier table having a plurality of rules representing a search space for packet classification, the plurality of rules having at least one field, the plurality of nodes each covering a portion of the search space by representing successively smaller subsets of the plurality of rules with increasing depth in the decision tree data structure; for each node of the decision tree data structure, (a) computing a node scope value indicating a node portion of the search space covered by the node; (b) for each rule intersecting the node, computing a rule scope value indicating a rule portion of the node portion covered by the rule; (c) comparing the node portion of the search space covered by the node to an amount of the node portion covered by rules intersecting the node by computing a scope factor for the node based on the node scope value computed and the rule scope value computed for each rule; and using the scope factor computed for at least one node of the plurality of nodes as an input parameter to a decision for performing a compiler operation at the at least one node.