func (qs *QuadStore) optimizeAndIterator(it *iterator.And) (graph.Iterator, bool) {
// Fail fast if nothing can happen
if clog.V(4) {
clog.Infof("Entering optimizeAndIterator %v", it.UID())
}
found := false
for _, it := range it.SubIterators() {
if clog.V(4) {
clog.Infof("%v", it.Type())
}
if it.Type() == mongoType {
found = true
}
}
if !found {
if clog.V(4) {
clog.Infof("Aborting optimizeAndIterator")
}
return it, false
}
newAnd := iterator.NewAnd(qs)
var mongoIt *Iterator
for _, it := range it.SubIterators() {
switch it.Type() {
case mongoType:
if mongoIt == nil {
mongoIt = it.(*Iterator)
} else {
newAnd.AddSubIterator(it)
}
case graph.LinksTo:
continue
default:
newAnd.AddSubIterator(it)
}
}
stats := mongoIt.Stats()
lset := []graph.Linkage{
{
Dir: mongoIt.dir,
Value: qs.ValueOf(mongoIt.name),
},
}
n := 0
for _, it := range it.SubIterators() {
if it.Type() == graph.LinksTo {
lto := it.(*iterator.LinksTo)
// Is it more effective to do the replacement, or let the mongo check the linksto?
ltostats := lto.Stats()
if (ltostats.ContainsCost+stats.NextCost)*stats.Size > (ltostats.NextCost+stats.ContainsCost)*ltostats.Size {
continue
}
newLto := NewLinksTo(qs, lto.SubIterators()[0], "quads", lto.Direction(), lset)
newAnd.AddSubIterator(newLto)
n++
}
}
if n == 0 {
return it, false
}
return newAnd.Optimize()
}
