Adding Edges to XDB

#xdb

An edge is a directed relationship between two nodes. Edges can be used to represent many different kinds of relationships in domain models, such as:

  • A user following another user
  • A user liking a post
  • A user commenting on a post
  • Posts/comments authored by a user

Edges are made of a source node, a target node, and a name. The name is used to distinguish between different kinds of edges between the same two nodes.

Edges of same name in a source node are ordered by creation time. Custom ordering is supported by passing a Score during edge creation.

Edges also support storing attributes, which can be used to store additional information about the relationship.

API

Creating edges is similar to creating attributes:

var store xdb.Store
 
user := xdb.NewKey("User", "123")
post := xdb.NewKey("Post", "456")
 
edges := []*xdb.Edge{
  xdb.NewEdge(user, "liked", post)
  xdb.NewEdge(post, "liked_by", user)
  xdb.NewEdge(post, "author", user, xdb.Score(1.0))
}
 
err := store.PutEdges(ctx, edges...)

There are two ways to query edges:

Get an edge by its source, target, and name. This returns the edge along with its score and attributes. This is useful when you want to get a specific edge or check if an edge exists.

user := xdb.NewKey("User", "123")
post := xdb.NewKey("Post", "456")
 
edgeRefs := []*xdb.Edge{
  xdb.NewEdge(user, "liked", post)
  xdb.NewEdge(post, "liked_by", user)
  xdb.NewEdge(post, "author", user)
}
 
edges, missing, err := store.GetEdges(ctx, edgeRefs...)

Or get a list of edges of a given name from a source node. This is useful when you want to iterate or paginate over a list of edges.

user := xdb.NewKey("User", "123")
 
q := xdb.NewEdgeQuery(user, "liked", xdb.Page(1,50))
 
edges, err := store.QueryEdges(ctx, q)