4. The method of claim 3 , further comprising: determining whether each of the transformed matches partially match the same tree pattern; if not, then determining that no candidate match can be derived; and if so, then determining whether the same candidate match is returned by multiple OP node children.
3. The method of claim 2 , further comprising: inputting an operator in an execution plan that is an OP node having arity K; inputting matches for children of the OP node to obtain fully-matched OP node children; and promoting each of the fully-matched OP node children into an equivalent form in terms of the OP node to obtain transformed matches.