func ExampleIts() {
var its []x.Instruction
for t := 0; t < 10; t++ {
var i x.Instruction
i.NanoTs = int64(100 - t)
its = append(its, i)
}
sort.Sort(x.Its(its))
fmt.Println(its[0].NanoTs)
// Output: 91
}
func (n *Update) doExecute(c *req.Context, its *[]*x.Instruction) error {
for pred, val := range n.edges {
if len(n.source) == 0 {
return errors.New(fmt.Sprintf(
"No source specified for id: %v kind: %v", n.id, n.kind))
}
i := new(x.Instruction)
i.SubjectId = n.id
i.SubjectType = n.kind
i.Predicate = pred
if b, err := json.Marshal(val); err != nil {
return err
} else {
i.Object = b
}
i.Source = n.source
i.NanoTs = n.NanoTs
log.WithField("instruction", i).Debug("Pushing to list")
*its = append(*its, i)
}
if len(n.children) == 0 {
return nil
}
if len(n.source) == 0 {
return errors.New(fmt.Sprintf(
"No source specified for id: %v kind: %v", n.id, n.kind))
}
// Children can only be added, not deleted via API. But they can be stopped
// from being retrieved.
// Scenario: How do I stop childA from being retrieved?
// Answer:
// Modify child by adding a 'deleted' edge
// Get(ChildKind, ChildId).Set("deleted", true).Execute(c)
//
// Then for retrieval from parent:
// NewQuery(ParentKind, ParentId).Collect(ChildKind).FilterOut("deleted")
// This would remove all children with a 'deleted' edge.
// Better still
// Get(ChildKind, ChildId).MarkDeleted().Execute(c)
// would automatically filter out that child and it's children
// from being retrieved.
for _, child := range n.children {
if len(child.id) > 0 {
log.WithField("child_id", child.id).Fatal(
"Child id should be empty for all current use cases")
return errors.New("Non empty child id")
}
for idx := 0; ; idx++ { // Retry loop.
child.id = x.UniqueString(c.NumCharsUnique)
log.WithField("id", child.id).Debug("Checking availability of new id")
if isnew := Get().IsNew(child.id); isnew {
log.WithField("id", child.id).Debug("New id available")
break
}
if idx >= 30 {
return errors.New("Unable to find new id")
}
}
// Create edge from parent to child
i := new(x.Instruction)
i.SubjectId = n.id
i.SubjectType = n.kind
i.Predicate = child.kind
i.ObjectId = child.id
i.Source = n.source
i.NanoTs = n.NanoTs
log.WithField("instruction", i).Debug("Pushing to list")
*its = append(*its, i)
// Create edge from child to parent
i = new(x.Instruction)
i.SubjectId = child.id
i.SubjectType = child.kind
i.Predicate = "_parent_"
i.ObjectId = n.id
i.Source = n.source
i.NanoTs = n.NanoTs
log.WithField("instruction", i).Debug("Pushing to list")
*its = append(*its, i)
if err := child.doExecute(c, its); err != nil {
return err
}
}
return nil
}