initial mongo indexed linksto

graph/mongo/quadstore_iterator_optimize.go

@@ -15,6 +15,8 @@
 package mongo
 
 import (
+	"github.com/barakmich/glog"
+
 	"github.com/google/cayley/graph"
 	"github.com/google/cayley/graph/iterator"
 )
@@ -23,11 +25,68 @@ func (qs *QuadStore) OptimizeIterator(it graph.Iterator) (graph.Iterator, bool)
 	switch it.Type() {
 	case graph.LinksTo:
 		return qs.optimizeLinksTo(it.(*iterator.LinksTo))
+	case graph.And:
+		return qs.optimizeAndIterator(it.(*iterator.And))
 
 	}
 	return it, false
 }
 
+func (qs *QuadStore) optimizeAndIterator(it *iterator.And) (graph.Iterator, bool) {
+	// Fail fast if nothing can happen
+	glog.V(4).Infoln("Entering optimizeAndIterator", it.UID())
+	found := false
+	for _, it := range it.SubIterators() {
+		glog.V(4).Infoln(it.Type())
+		if it.Type() == mongoType {
+			found = true
+		}
+	}
+	if !found {
+		glog.V(4).Infoln("Aborting optimizeAndIterator")
+		return it, false
+	}
+
+	newAnd := iterator.NewAnd(qs)
+	var firstmongo *Iterator
+	for _, it := range it.SubIterators() {
+		switch it.Type() {
+		case mongoType:
+			if firstmongo == nil {
+				firstmongo = it.(*Iterator)
+			} else {
+				newAnd.AddSubIterator(it)
+			}
+		case graph.LinksTo:
+			continue
+		default:
+			newAnd.AddSubIterator(it)
+		}
+	}
+
+	lset := []graph.LinkageSet{
+		{
+			Dir:    firstmongo.dir,
+			Values: []graph.Value{qs.ValueOf(firstmongo.name)},
+		},
+	}
+
+	ltocount := 0
+	for _, it := range it.SubIterators() {
+		if it.Type() == graph.LinksTo {
+			lto := it.(*iterator.LinksTo)
+			newLto := NewLinksTo(qs, lto.SubIterators()[0], "quads", lto.Direction(), lset)
+			newAnd.AddSubIterator(newLto)
+			ltocount++
+		}
+	}
+	if ltocount == 0 {
+		return it, false
+	}
+
+	return newAnd.Optimize()
+}
+
 func (qs *QuadStore) optimizeLinksTo(it *iterator.LinksTo) (graph.Iterator, bool) {
 	subs := it.SubIterators()
 	if len(subs) != 1 {