func buildIteratorTree(tree *peg.ExpressionTree, ts graph.TripleStore) graph.Iterator {
switch tree.Name {
case "Start":
return buildIteratorTree(tree.Children[0], ts)
case "NodeIdentifier":
var out graph.Iterator
nodeID := getIdentString(tree)
if tree.Children[0].Name == "Variable" {
allIt := ts.GetNodesAllIterator()
allIt.AddTag(nodeID)
out = allIt
} else {
n := nodeID
if tree.Children[0].Children[0].Name == "ColonIdentifier" {
n = nodeID[1:]
}
fixed := ts.MakeFixed()
fixed.AddValue(ts.GetIdFor(n))
out = fixed
}
return out
case "PredIdentifier":
i := 0
if tree.Children[0].Name == "Reverse" {
//Taken care of below
i++
}
it := buildIteratorTree(tree.Children[i], ts)
lto := graph.NewLinksToIterator(ts, it, "p")
return lto
case "RootConstraint":
constraintCount := 0
and := graph.NewAndIterator()
for _, c := range tree.Children {
switch c.Name {
case "NodeIdentifier":
fallthrough
case "Constraint":
it := buildIteratorTree(c, ts)
and.AddSubIterator(it)
constraintCount++
continue
default:
continue
}
}
return and
case "Constraint":
var hasa *graph.HasaIterator
topLevelDir := "s"
subItDir := "o"
subAnd := graph.NewAndIterator()
isOptional := false
for _, c := range tree.Children {
switch c.Name {
case "PredIdentifier":
if c.Children[0].Name == "Reverse" {
topLevelDir = "o"
subItDir = "s"
}
it := buildIteratorTree(c, ts)
subAnd.AddSubIterator(it)
continue
case "PredicateKeyword":
switch c.Children[0].Name {
case "OptionalKeyword":
isOptional = true
}
case "NodeIdentifier":
fallthrough
case "RootConstraint":
it := buildIteratorTree(c, ts)
l := graph.NewLinksToIterator(ts, it, subItDir)
subAnd.AddSubIterator(l)
continue
default:
continue
}
}
hasa = graph.NewHasaIterator(ts, subAnd, topLevelDir)
if isOptional {
optional := graph.NewOptionalIterator(hasa)
return optional
}
return hasa
default:
return &graph.NullIterator{}
}
panic("Not reached")
}
func (m *MqlQuery) buildResultIterator(path MqlPath) graph.Iterator {
all := m.ses.ts.GetNodesAllIterator()
all.AddTag(string(path))
return graph.NewOptionalIterator(all)
}