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Enumerate iterator types

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This commit is contained in:
kortschak 2014-07-03 09:57:31 +09:30
parent 1f67913ed9
commit cd46452b63
23 changed files with 145 additions and 68 deletions
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14
graph/iterator/and_iterator_optimize.go
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@ -134,7 +134,7 @@ func (_ *And) optimizeReplacement(its []graph.Iterator) graph.Iterator {
func optimizeOrder(its []graph.Iterator) []graph.Iterator {
var (
// bad contains iterators that can't be (efficiently) nexted, such as
// "optional" or "not". Separate them out and tack them on at the end.
// graph.Optional or graph.Not. Separate them out and tack them on at the end.
out, bad []graph.Iterator
best graph.Iterator
bestCost = int64(1 << 62)
@ -257,25 +257,25 @@ func optimizeSubIterators(its []graph.Iterator) []graph.Iterator {
// Check a list of iterators for any Null iterators.
func hasAnyNullIterators(its []graph.Iterator) bool {
for _, it := range its {
if it.Type() == "null" {
if it.Type() == graph.Null {
return true
}
}
return false
}
// There are two "not-useful" iterators -- namely "null" which returns
// nothing, and "all" which returns everything. Particularly, we want
// to see if we're intersecting with a bunch of "all" iterators, and,
// There are two "not-useful" iterators -- namely graph.Null which returns
// nothing, and graph.All which returns everything. Particularly, we want
// to see if we're intersecting with a bunch of graph.All iterators, and,
// if we are, then we have only one useful iterator.
func hasOneUsefulIterator(its []graph.Iterator) graph.Iterator {
usefulCount := 0
var usefulIt graph.Iterator
for _, it := range its {
switch it.Type() {
case "null", "all":
case graph.Null, graph.All:
continue
case "optional":
case graph.Optional:
// Optional is weird -- it's not useful, but we can't optimize
// away from it. Therefore, we skip this optimization
// if we see one.