simple cayley mql for duplicate subject detection

main.go

package main

import (
	"fmt"
	"net/http"

	"github.com/google/cayley"
	"github.com/google/cayley/graph"
	"github.com/google/cayley/quad"
	"github.com/google/cayley/query/mql"
	"github.com/pborman/uuid"

	_ "github.com/google/cayley/graph/bolt"
)

func main() {
	fmt.Println("Initializing server...")

	dbPath := "/tmp/graphdb.nq"
	graph.InitQuadStore("bolt", dbPath, nil)
	store, err := cayley.NewGraph("bolt", dbPath, nil)
	if err != nil {
		fmt.Println("[Error] could not open '", dbPath, "': ", err)
		return
	}

	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		sess := mql.NewSession(store.QuadStore)
		c := make(chan interface{}, 5)
		username := "flynn"
		query := `[{"id": null, "name": "` + username + `"}]`
		fmt.Println("query: '", query, "'")
		sess.Execute(query, c, -1)
		if len(c) > 0 {
			fmt.Println("[Error] user '", username, "' already exists")
			return
		}
		fmt.Println("username is unique: ", username)

		userid := graph.NewUniqueKey("") // we ASSUME it actually does create a NewUniqueKey
		useridStr := userid.String()
		if uuid.Parse(useridStr) == nil {
			fmt.Println("[Error] unable to parse unique userid")
			return
		}
		fmt.Println("userid: ", useridStr)

		tx := graph.NewTransaction()
		tx.AddQuad(quad.Quad{useridStr, "name", username, ""})

		io := graph.IgnoreOpts{IgnoreDup: false, IgnoreMissing: false}
		err := store.ApplyDeltas(tx.Deltas, io)
		if err != nil {
			fmt.Println("[Error] unable to update database: ", err)
			return
		}
	})

	fmt.Println("Server is at http://localhost:8080/")
	http.ListenAndServe(":8080", nil)
}