Query optimizer tuning

Set the optimization method used for cost-based optimization in sa.amos to the method named m.

   optmethod(Charstring m) -> Charstring old

Three optimization modes for AmosQL queries can be chosen: ranksort: (default) is fast but not always optimal.
exhaustive: is optimal but it may slow down the optimizer considerably. randomopt: is a combination of two random optimization heuristics: Iterative improvement and sequence heuristics Nas93. optmethod returns the old setting of the optimization method.

Random optimization can be tuned by using the function:

   optlevel(Integer i,Integer j);

where i and j are integers specifying number of iterations in iterative improvement and sequence heuristics, respectively. Default settings is i=5 and j=5.

Reoptimize function f:

   reoptimize(Function f) -> Boolean

Reoptimize function named fn:

   reoptimize(Charstring fn) -> Boolean