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