Neo4j more efficient Cypher query for finding connected nodes with a relationship

The name of the pictureThe name of the pictureThe name of the pictureClash Royale CLAN TAG#URR8PPP



Neo4j more efficient Cypher query for finding connected nodes with a relationship



I have a patch where I know a starting and end node with an unknown number of nodes between the 2. I wish to collect a collection of nodes and each nodes exiting relationship in the chain.


PROFILE MATCH p = (:Questionid:'1234')-[:Answer*0..3]->(t)-
[:Answer]->(:Questionid:'5678')
WHERE t:Set OR t:Read
OPTIONAL MATCH (x)-[v:Answer]->(y)
WHERE x.id <> '1234' and x IN nodes(p) AND v IN rels(p)
return x,v



This query is pretty inefficient as the OPTIONAL MATCH (x)-[v:Answer]->(y) requires a full nodes scan.


OPTIONAL MATCH (x)-[v:Answer]->(y)



I know that t and as a result x will be of types Set or Read which would reduce the scan quite a bit but don't think there is a way to query this.


t


x


Set


Read



Is there any way to optimise this?




1 Answer
1



You can simply unwind the path you have already got:


MATCH p = (:Questionid:'1234')-[:Answer*0..3]->(t)-[:Answer]->(:Questionid:'5678')
WHERE t:Set OR t:Read
WITH nodes(p) AS nds,
rels(p) AS rls
UNWIND range(1, length(nds)-2) AS i
RETURN nds[i] AS x,
rls[i] AS v





That looks great! I assume the range function will need some check for null as there may be no nodes in the path?
– Sheff
Aug 10 at 14:19





@Sheff But why? The lengths of arrays of nodes and relations are already known.
– stdob--
Aug 10 at 14:24





@Sheff Of course, you can add a check that the length of an array of nodes is greater than two.
– stdob--
Aug 10 at 14:26





I see what you mean. The issue is that the path I am querying may not exist (which I didn't mention in my question) hence the possibility of a null nds
– Sheff
Aug 10 at 14:32


nds






By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

-

Popular posts from this blog

Firebase Auth - with Email and Password - Check user already registered

Image
Clash Royale CLAN TAG #URR8PPP Firebase Auth - with Email and Password - Check user already registered I want to check when a user attempts to signup with createUserWithEmailAndPassword() in Firebase user Authentication method, this user is already registered with my app. createUserWithEmailAndPassword() 8 Answers 8 To detect whether a user with that email address already exists, you can detect when the call to createUserWithEmailAndPassword () fails with auth/email-already-in-use . I see that @Srinivasan just posted an answer for this. createUserWithEmailAndPassword () auth/email-already-in-use Alternatively, you can detect that an email address is already used by calling fetchSignInMethodsForEmail() (previous called fetchProvidersForEmail() ). fetchSignInMethodsForEmail() fetchProvidersForEmail() When the user trying to create an user with same email address, the task response will be "Response: The email address is already in use by another account." mFirebas
Read more

Dynamically update html content plain JS

Image
Clash Royale CLAN TAG #URR8PPP Dynamically update html content plain JS So I have a script bound in my index.html, which literally has to fetch an array of jsons from an api, then dynamically update my page when get response. But as a result I'm getting an as the only update of my page. here is my script fetch(url) .then((resp) => resp.json()) .then((resp) => resp.results.forEach(item => fetch(item.url) .then((response)=> response.json()) .then((response) => pokeArr.push(response)) .catch(console.log) ) ).catch(console.log) const filler = () => if(!pokeArr) return 0 pokeArr.map((i,j)=> return `<tr>$i.name</tr>` ) const pokeindex = () => document.getElementById('a').appendChild(document.createElement(filler())) pokeindex() When I'm consoling it, I can see in the console all the responses I get, so I'm at least doing the fetching part right. What's parberakan ? What's pokeArr ? – T.J. Crowder Aug 8 at 12
Read more

How to determine optimal route across keyboard

Image
Clash Royale CLAN TAG #URR8PPP How to determine optimal route across keyboard I'm trying to automate the typing process in a video game. Players are given an on-screen QWERTY keyboard layout that they can navigate with the control stick (up, down, left, right) in order to select a letter to type. I was wondering if there was a module for Python (or some other resource I could explore) that would help my program find a path across the keyboard as it types each letter in a given message. In other words, if the first letter typed was "A" and the next letter was "B", the module would know that the program should move 1 space down on the keyboard and 4 spaces to the right. Currently, I have the program resetting to the "G" key after each letter is typed (allowing me to use fixed-directions as the program parses each character in the desired message). As you can imagine, this is quite inefficient and defeats the purpose of automating the typing in the fir
Read more