void genconstraint(StringBuilder buf) {
int nprojections = random.nextInt(NPROJECTIONS);
int nselections = random.nextInt(NSELECTIONS);
if (nprojections + nselections == 0) nprojections++; // guarantee non-null constraint
projections = new ArrayList<BaseType>();
// generate candidate projection list
while (projections.size() < nprojections) {
BaseType node = choose(allnodes);
// check for conflicts
if (projections.contains(node)) continue; // no duplicates
if (containsChild(node, projections)) continue; // child => !parent
BaseType parent = containsParent(node, projections);
if (parent != null) projections.remove(parent); // parent && child => !parent
projections.add(node);
}
projections = sort(projections); // sort
for (int i = 0; i < projections.size(); i++) {
BaseType node = projections.get(i);
if (i > 0) buf.append(",");
genprojection(node, buf);
}
selections = new ArrayList<BaseType>();
valuelist = new ArrayList<BaseType>();
// generate candidate selection list
while (selections.size() < nselections) {
BaseType node = choose(leaves);
if (selections.contains(node)) continue; // no duplicates
// conflict avoidance
if (projections.contains(node)) continue; // no duplicates with projection list
if (containsChild(node, projections)) continue; // child => !parent wrt projection list
BaseType parent = containsParent(node, projections);
if (parent != null) continue; // project parent && select child => remove child
selections.add(node);
}
for (int i = 0; i < nselections; i++) {
BaseType node = selections.get(i);
buf.append("&");
genselection(node, buf);
}
}
BaseType findmatchingvar(BaseType var) {
assert (isprimitive(var));
BaseType match = null;
for (BaseType bt : leaves) {
if (bt == var) continue;
if (sametype(bt, var)) {
// make sure that this var does not cause conflict
if (selections.contains(bt)) continue;
if (projections.contains(bt)) continue;
if (valuelist.contains(bt)) continue;
BaseType parent = containsParent(bt, projections);
if (parent != null) continue;
match = bt;
valuelist.add(bt);
}
}
return match;
}