Check if user liked the post - neo4j

Question

I have the following query:
MATCH (user:User)-[:CREATED]->(post:Post)
WITH user, post
ORDER BY post.createdAt DESC
OPTIONAL MATCH (post)<-[:BELONGS_TO]-(comment:Comment)<-[:COMMENTED]-(:User)
WITH user, post, liked, comment
ORDER BY comment.timestamp DESC
WITH user, post, liked, COLLECT(comment)[0..4] AS comments
RETURN post,
{ username: user.username,
firstName: user.firstName,
lastName: user.lastName,
profilePicture: user.profilePicture
} AS createdBy,
size((post)<-[:LIKES]-(:User)) AS likes,
liked,
comments
SKIP {skip}
LIMIT {limit}
The query gets list of posts and calculates other things like:
get post comments, get user who created the post, get total number of likes.
I need to also calculate if I liked the post or not, which will result into: userLiked (true|false).
I was thinking of something like:
OPTIONAL MATCH (post)<-[userLiked:LIKES]-(:User {uuid: {userUUID}})

Answer 1

If you just need a true/false, then EXISTS() is a better option.
You can also improve performance by moving your SKIP and LIMIT from the end of your query to after your ORDER BY for the post creation.
If you're using Neo4j 3.1.x or higher, you can use map projection to make it a little easier to return the fields you need on the createdBy map.
Here's your query with all these things included:
MATCH (user:User)-[:CREATED]->(post:Post)
WITH user, post
ORDER BY post.createdAt DESC
OPTIONAL MATCH (post)<-[:BELONGS_TO]-(comment:Comment)<-[:COMMENTED]-(:User)
WITH user, post, comment
ORDER BY comment.timestamp DESC
WITH user, post, COLLECT(comment)[..4] AS comments
SKIP {skip} LIMIT {limit}
RETURN post,
user { .username, .firstName, .lastName, .profilePicture } AS createdBy,
size((post)<-[:LIKES]-(:User)) AS likes,
exists((post)<-[:LIKES]-(:User{uuid: {userUUID}})) AS userLiked,
comments