如何使用MERGE保存内部对象

Question

For now I am using save method from GraphRepository and I also have constraint on user id, it is unique . User have List of users - friends. My flow:

1. Read from db, if user is null save his with friends, I am using save method from GraphRepository

2. But if user is present i just need to update him and update his friends. I am using custom query into DAO method

    @Query("MERGE (u:User {id:{user}.id}) " + "ON CREATE SET u.id = {user}.id, u.firstName={user}.firstName, u.lastName={user}.lastName, u.imgUrl = {user}.imgUrl " + "ON MATCH SET u.id += {user}.id, u.firstName+={user}.firstName, u.lastName+={user}.lastName, u.imgUrl += {user}.imgUrl") void mergeUser(@Param("user") User user); 

   But with merge method i can't add all user's friends and ON MATCH case doesn't work too

Answer 1

You probably want to use a Cypher query that looks something like this:

MERGE (u:User {id:{user}.id})
SET u.firstName = {user}.firstName, u.lastName = {user}.lastName, u.imgUrl = {user}.imgUrl
WITH u
UNWIND {friends} AS friend
MERGE (f:User {id:{friend}.id})
SET f.firstName = {friend}.firstName, f.lastName = {friend}.lastName, f.imgUrl = {friend}.imgUrl
MERGE (u)-[:FRIEND_OF]->(f);

There is no need to use ON CREATE or ON MATCH , since you always want to do the same thing either way. Also, there is no need to explicitly assign to the id property, since MERGE will guarantee that the node will have the desired id value.

I assume that friends collection consists of maps that have the same keys as your user map.