Cypher Performance with Multiple Relations - neo4j

I am tasked with prototyping Neo4J as a replacement to our existing data mart which stores data in Redshift/Postgres schemas. I have loaded an instance of neo running on an EC2 instance on an m5.xlarge server to model a marketing campaign and trying to get simple counts of who saw my spots in a given demographic. The results as far as numbers produced are the exact same as my existing data mart, but i am surprised to see that performance is much slower. The same query to get simple count of impressions by a television network returns in 48 seconds compared to 1.5 seconds in Redshift. Question is am I doing something wrong in my cypher (i.e. too many joins) or is this expected behavior. Here is a diagram of the model:
Here is my Cypher to get the results in 48s:
match (c:Campaign{campaign_id:98})<-[:PART_OF]-(sa)
, (sa)-[:AIRED_ON]->(n)
, (n)-[:BELONGS_TO]->(ng:NetworkGroup{network_group_id:2})
, (sa)<-[:EXPOSED_WITH]-(e)
, (e)<-[se:CONTAINS_ENTITY]-(s:Sample{sample_id:2000005})
, (e)-[:MEMBER_OF]->(a:DemographicAudience{audience_id:2})
return c.campaign_id as `campaign_id`
, a.audience_id as `audience_id`
, a.audience_name as `audience_name`
, s.sample_id as `sample_id`
, n.network_id as `network_id`
, n.network_name as `network_name`
, n.network_call_sign as `network_call_sign`
, count(distinct sa.spot_airing_id) as `spot_airings`
, sum(se.weight) as `spot_impressions`
In addition, I believe all necessary constraints are added to optimize:
Indexes
ON :DemographicAudience(audience_id) ONLINE (for uniqueness constraint)
ON :Campaign(campaign_id) ONLINE (for uniqueness constraint)
ON :Entity(entity_id) ONLINE (for uniqueness constraint)
ON :Network(network_id) ONLINE (for uniqueness constraint)
ON :NetworkGroup(network_group_id) ONLINE (for uniqueness constraint)
ON :Sample(sample_id) ONLINE (for uniqueness constraint)
ON :SpotAiring(spot_airing_id) ONLINE (for uniqueness constraint)
Constraints
ON ( audience:DemographicAudience ) ASSERT audience.audience_id IS UNIQUE
ON ( campaign:Campaign ) ASSERT campaign.campaign_id IS UNIQUE
ON ( entity:Entity ) ASSERT entity.entity_id IS UNIQUE
ON ( network:Network ) ASSERT network.network_id IS UNIQUE
ON ( networkgroup:NetworkGroup ) ASSERT networkgroup.network_group_id IS UNIQUE
ON ( sample:Sample ) ASSERT sample.sample_id IS UNIQUE
ON ( spotairing:SpotAiring ) ASSERT spotairing.spot_airing_id IS UNIQUE
Running Neo4J 3.3.1 Community on AWS: https://aws.amazon.com/marketplace/pp/B073S5MDPV/?ref_=_ptnr_intuz_ami_neoj4
I should also mention that quite a bit of data is loaded: 24,154,440 nodes and 33,220,694 relationships. Most of these are relationships to entities.
My understanding was that Neo4J should hold toe to toe with any RDBMS and even outperform as data grows. I'm hoping I am just being naive with my rookie cypher skills. Any help would be appreciated.
Thanks.

Keep in mind that in Neo4j indexes are used to find starting points in the graph, and once those starting points are found, relationship traversal is used to expand out to find the paths which fit the pattern.
In this case we have several unique nodes, so we can save on some operations by ensuring that we match to all of these nodes first, and we should see Expand(Into) in our query plan instead of Expand(All) and then Filter. I have a hunch that the planner is only using index lookup on a single node, and the rest of them aren't using the index but using property access and filtering, which is less efficient.
In the case that the planner doesn't lookup all your unique nodes first, before expansion, we can force it by introducing a LIMIT 1 after the initial match.
Lastly, it's a good idea to aggregate using the node itself rather than its properties if the properties in question are unique. This will use the underlying graph id for the node for comparison purposes rather than having to do more expensive property access.
Give this a try and see how it compares:
MATCH (c:Campaign{campaign_id:98}), (s:Sample{sample_id:2000005}), (a:DemographicAudience{audience_id:2}), (ng:NetworkGroup{network_group_id:2})
WITH c,s,a,ng
LIMIT 1
MATCH (c)<-[:PART_OF]-(sa)
, (sa)-[:AIRED_ON]->(n)
, (n)-[:BELONGS_TO]->(ng)
, (sa)<-[:EXPOSED_WITH]-(e)
, (e)<-[se:CONTAINS_ENTITY]-(s)
, (e)-[:MEMBER_OF]->(a)
WITH c, a, s, n, count(distinct sa) as `spot_airings`, sum(se.weight) as `spot_impressions`
RETURN c.campaign_id as `campaign_id`
, a.audience_id as `audience_id`
, a.audience_name as `audience_name`
, s.sample_id as `sample_id`
, n.network_id as `network_id`
, n.network_name as `network_name`
, n.network_call_sign as `network_call_sign`
, `spot_airings`
, `spot_impressions`

Related

Auto increment id Neo4j to retrieve elements in insert order

Recently, I am experimenting Neo4j. I like the idea but I am facing a problem that I have never faced with relational databases.
I want to perform these inserts and then return them exactly in the insertion order.
Insert elements:
create(p1:Person {name:"Marc"})
create(p2:Person {name:"John"})
create(p3:Person {name:"Paul"})
create(p4:Person {name:"Steve"})
create(p5:Person {name:"Andrew"})
create(p6:Person {name:"Alice"})
create(p7:Person {name:"Bob"})
While to return them:
match(p:Person) return p order by id(p)
I receive the elements in the following order:
Paul
Andrew
Marc
John
Steve
Alice
Bob
I note that these elements are not returned respecting the query insertion order (through the id function).
In fact the id of my elements are the following:
Marc: 18221
John: 18222
Paul: 18208
Steve: 18223
Andrew: 18209
Alice: 18224
Bob: 18225
How does the Neo4j id function work? I read that it generates an auto incremental id but it seems a little strange his mechanism. How do I return items respecting the query insertion order? I thought about creating a timestamp attribute for each node but I don't think it's the best choice
If you're looking to generate sequence numbers in Neo4j then you need to manage this yourself using a strategy that works best in your application.
In ours we maintain sequence numbers in key/value pair nodes where Scope is the application name given to the sequence number range, and Value is the last sequence number used. When we generate a node of a given type, such as Product, then we increment the sequence number and assign it to our new node.
MERGE (n:Sequence {Scope: 'Product'})
SET n.Value = COALESCE(n.Value, 0) + 1
WITH n.Value AS seq
CREATE (product:Product)
SET product.UniqueId = seq
With this you can create as many sequence numbers you need just by creating sequence nodes with unique scope names.
For more examples and tests see the AutoInc.Neo4j project https://github.com/neildobson-au/AutoInc/blob/master/src/AutoInc.Neo4j/Neo4jUniqueIdGenerator.cs
The id of Neo4j is maintained internally, which your business code should not depend on.
Generally it's auto incrementally, but if there is delete operation, you may reuse the deleted id according to the Reuse Policy of Neo4j Server.

Low performance of neo4j

I am server engineer in company that provide dating service.
Currently I am building a PoC for our new recommendation engine.
I try to use neo4j. But performance of this database does not meet our needs.
I have strong feeling that I am doing something wrong and neo4j can do much better.
So can someone give me an advice how to improve performance of my Cypher’s query or how to tune neo4j in right way?
I am using neo4j-enterprise-2.3.1 which is running on c4.4xlarge instance with Amazon Linux.
In our dataset each user can have 4 types of relationships with others users - LIKE, DISLIKE, BLOCK and MATCH.
Also he has a properties like countryCode, birthday and gender.
I made import of all our users and relationships from RDBMS to neo4j using neo4j-import tool.
So each user is a node with properties and each reference is a relationship.
The report from neo4j-import tool said that :
2 558 667 nodes,
1 674 714 539 properties and
1 664 532 288 relationships
were imported.
So it’s huge DB :-) In our case some nodes can have up to 30 000 outgoing relationships..
I made 3 indexes in neo4j :
Indexes
ON :User(userId) ONLINE
ON :User(countryCode) ONLINE
ON :User(birthday) ONLINE
Then I try to build online recommendation engine using this query :
MATCH (me:User {userId: {source_user_id} })-[:LIKE | :MATCH]->()<-[:LIKE | :MATCH]-(similar:User)
USING INDEX me:User(userId)
USING INDEX similar:User(birthday)
WHERE similar.birthday >= {target_age_gte} AND
similar.birthday <= {target_age_lte} AND
similar.countryCode = {target_country_code} AND
similar.gender = {source_gender}
WITH similar, count(*) as weight ORDER BY weight DESC
SKIP {skip_similar_person} LIMIT {limit_similar_person}
MATCH (similar)-[:LIKE | :MATCH]-(recommendation:User)
WITH recommendation, count(*) as sheWeight
WHERE recommendation.birthday >= {recommendation_age_gte} AND
recommendation.birthday <= {recommendation_age_lte} AND
recommendation.gender= {target_gender}
WITH recommendation, sheWeight ORDER BY sheWeight DESC
SKIP {skip_person} LIMIT {limit_person}
MATCH (me:User {userId: {source_user_id} })
WHERE NOT ((me)--(recommendation))
RETURN recommendation
here is the execution plan for one of the user :
plan
When I executed this query for list of users I had the result :
count=2391, min=4565.128849, max=36257.170065, mean=13556.750555555178, stddev=2250.149335254768, median=13405.409811, p75=15361.353029999998, p95=17385.136478, p98=18040.900481, p99=18426.811424, p999=19506.149138, mean_rate=0.9957385490980866, m1=1.2148195797996817, m5=1.1418078036067119, m15=0.9928564378521962, rate_unit=events/second, duration_unit=milliseconds
So even the fastest is too slow for Real-time recommendations..
Can you tell me what I am doing wrong?
Thanks.
EDIT 1 : plan with the expanded boxes :
I built an unmanaged extension to see if I could do better than Cypher. You can grab it here => https://github.com/maxdemarzi/social_dna
This is a first shot, there are a couple of things we can do to speed things up. We can pre-calculate/save similar users, cache things here and there, and random other tricks. Give it a shot, let us know how it goes.
Regards,
Max
If I'm reading this right, it's finding all matches for users by userId and separately finding all matches for users by your various criteria. It's then finding all of the places that they come together.
Since you have a case where you're starting on the left with a single node, my guess is that we'd be better served by following the paths and then filtering what it gotten via relationship traversal.
Let's see how starting like this works for you:
MATCH
(me:User {userId: {source_user_id} })-[:LIKE | :MATCH]->()
<-[:LIKE | :MATCH]-(similar:User)
WITH similar
WHERE similar.birthday >= {target_age_gte} AND
similar.birthday <= {target_age_lte} AND
similar.countryCode = {target_country_code} AND
similar.gender = {source_gender}
WITH similar, count(*) as weight ORDER BY weight DESC
SKIP {skip_similar_person} LIMIT {limit_similar_person}
MATCH (similar)-[:LIKE | :MATCH]-(recommendation:User)
WITH recommendation, count(*) as sheWeight
WHERE recommendation.birthday >= {recommendation_age_gte} AND
recommendation.birthday <= {recommendation_age_lte} AND
recommendation.gender= {target_gender}
WITH recommendation, sheWeight ORDER BY sheWeight DESC
SKIP {skip_person} LIMIT {limit_person}
MATCH (me:User {userId: {source_user_id} })
WHERE NOT ((me)--(recommendation))
RETURN recommendation
[UPDATED]
One possible (and nonintuitive) cause of inefficiency in your query is that when you specify the similar:User(birthday) filter, Cypher uses an index seek with the :User(birthday) index (and additional tests for countryCode and gender) to find all possible DB matches for similar. Let's call that large set of similar nodes A.
Only after finding A does the query filter to see which of those nodes are actually connected to me, as specified by your MATCH pattern.
Now, if there are relatively few me to similar paths (as specified by the MATCH pattern, but without considering its WHERE clause) as compared to the size of A -- say, 2 or more orders of magnitude smaller -- then it might be faster to remove the :User label from similar (since I presume they are probably all going to be users anyway, in your data model), and also remove the USING INDEX similar:User(birthday) clause. In this case, not using the index for similar may actually be faster for you, since you will only be using the WHERE clause on a relatively small set of nodes.
The same considerations also apply to the recommendation node.
Of course, this all has to be verified by testing on your actual data.

CREATE UNIQUE with labels and properties

I'm using Neo4j 2.0.0-M06. Just learning Cypher and reading the docs. In my mind this query would work, but I should be so lucky...
I'm importing tweets to a mysql-database, and from there importing them to neo4j. If a tweet is already existing in the Neo4j database, it should be updated.
My query:
MATCH (y:Tweet:Socialmedia) WHERE
HAS (y.tweet_id) AND y.tweet_id = '123'
CREATE UNIQUE (n:Tweet:Socialmedia {
body : 'This is a tweet', tweet_id : '123', tweet_userid : '321', tweet_username : 'example'
} )
Neo4j says: This pattern is not supported for CREATE UNIQUE
The database is currently empty on nodes with the matching labels, so there are no tweets what so ever in the Neo4j database.
What is the correct query?
You want to use MERGE for this query, along with a unique constraint.
CREATE CONSTRAINT on (t:Tweet) ASSERT t.tweet_id IS UNIQUE;
MERGE (t:Tweet {tweet_id:'123'})
ON CREATE
SET t:SocialMedia,
t.body = 'This is a tweet',
t.tweet_userid = '321',
t.tweet_username = 'example';
This will use an index to lookup the tweet by id, and do nothing if the tweet exists, otherwise it will set those properties.
I would like to point that one can use a combination of
CREATE CONSTRAINT and then a normal
CREATE (without UNIQUE)
This is for cases where one expects a unique node and wants to throw an exception if the node unexpectedly exists. (Far cheaper than looking for the node before creating it).
Also note that MERGE seems to take more CPU cycles than a CREATE. (It also takes more CPU cycles even if an exception is thrown)
An alternative scenario covering CREATE CONSTRAINT, CREATE and MERGE (though admittedly not the primary purpose of this post).

Neo4j performance - is it really fast?

I'm wanting to run some tests on neo4j, and compare its performance with other databases, in this case postgresql.
This postgres database have about 2000000 'content's distributed around 3000 'categories'. ( this means that there is a table 'content', one 'category' and a relation table 'content-to-category' since one content can be in more than 1 category).
So, mapping this to a neo4j db, i'm creating nodes 'content', 'category' and their relations ( content to category, and content to content, cause contents can have related contents).
category -> category ( categories can have sub-categories )
content -> category
content -> content (related)
Do you think this 'schema' is ok for this type of domain ?
migrating all data from postgresql do neo4j: it is taking forever ( about 4, 5 days ). This is just some search for nodes and creating/updating accordingly. (search is using indexes and the insert/update if taking 500ms for each node)
Am i doing something wrong ?
Migration is done, so i went to try some querying ...
i ended up with about 2000000 content nodes, 3000 category nodes, and more than 4000000 relationships.
(please note that i'm new to all this neo4j world, so i have no idea how to optimize cypher queries...)
One of the queries i wanted to test is: get the 10 latest published contents of a given 'definition' in a given category (this includes contents that are in sub categories of the given category)
experimenting a little, i ended up with something like this :
START
c = node : node_auto_index( 'type: category AND code: category_code' ),
n = node : node_auto_index( 'type: content AND state: published AND definitionCode: definition_name' )
MATCH (c) <- [ r:BELONGS_TO * ] - (n)
RETURN n.published_stamp, n.title
ORDER BY n.published_stamp DESC
LIMIT 6
this takes around 3 seconds, excluding the first run, that takes a lot more ... is this normal ?
What am i doing wrong ?
please note that i'm using neo4j 1.9.2, and auto indexing some node properties ( type, code, state, definitionCode and published_stamp included - title is not auto indexed )
also, returning 'c' on the previous query ( start c = node : node_auto_index( 'type: category AND code : category-code' ) return c; ) is fast (again, excluding the first run, that takes aroung 20-30ms)
also, i'm not sure if this is the right way to use indexes ...
Thank you in advance (sorry if something is not making sense - ask me and i'll try to explain better).
Have you looked at the batch import facilities: http://www.neo4j.org/develop/import? You really should look at that for the initial import - it will take minutes instead of days.
I will ask some of our technical folks to get back to you on some of the other stuff. You really should not be seeing this.
Rik
How many nodes are returned by this?
START
n = node : node_auto_index( 'type: content AND state: published AND definitionCode: definition_name' )
RETURN count(*)
I would try to let the graph do the work.
How deep are your hierarchies usually?
Usually you limit arbitrary length relationships to not have the combinatorial explosion:
I would also have a different relationship-type between content and category than the category tree.
Can you point out your current relationship-types?
START
c = node : node_auto_index( 'type: category AND code: category_code' ),
MATCH (c) <- [:BELONGS_TO*5] - (n)
WHERE n.type = 'content' AND n.state='published' and n.definitionCode = 'definition_name'
RETURN n.published_stamp, n.title
ORDER BY n.published_stamp DESC
LIMIT 6
Can you try that?
For import it is easiest to generate CSV from your SQL and import that using http://github.com/jexp/batch-import
Are you running Linux, maybe on an ext4 filesystem?
You might want to set the barrier=0 mount option, as described here: http://structr.org/blog/neo4j-performance-on-ext4
Further discussion of this topic: https://groups.google.com/forum/#!topic/neo4j/nflUyBsRKyY

Can Neo4j be effectively used to show a collection of nodes in a sortable and filterable table?

I realise this may not be ideal usage, but apart from all the graphy goodness of Neo4j, I'd like to show a collection of nodes, say, People, in a tabular format that has indexed properties for sorting and filtering
I'm guessing the Type of a node can be stored as a Link, say Bob -> type -> Person, which would allow us to retrieve all People
Are the following possible to do efficiently (indexed?) and in a scalable manner?
Retrieve all People nodes and display all of their names, ages, cities of birth, etc (NOTE: some of this data will be properties, some Links to other nodes (which could be denormalised as properties for table display's and simplicity's sake)
Show me all People sorted by Age
Show me all People with Age < 30
Also a quick how to do the above (or a link to some place in the docs describing how) would be lovely
Thanks very much!
Oh and if the above isn't a good idea, please suggest a storage solution which allows both graph-like retrieval and relational-like retrieval
if you want to operate on these person nodes, you can put them into an index (default is Lucene) and then retrieve and sort the nodes using Lucene (see for instance How do I sort Lucene results by field value using a HitCollector? on how to do a custom sort in java). This will get you for instance People sorted by Age etc. The code in Neo4j could look like
Transaction tx = neo4j.beginTx();
idxManager = neo4j.index()
personIndex = idxManager.forNodes('persons')
personIndex.add(meNode,'name',meNode.getProperty('name'))
personIndex.add(youNode,'name',youNode.getProperty('name'))
tx.success()
tx.finish()
'*** Prepare a custom Lucene query context with Neo4j API ***'
query = new QueryContext( 'name:*' ).sort( new Sort(new SortField( 'name',SortField.STRING, true ) ) )
results = personIndex.query( query )
For combining index lookups and graph traversals, Cypher is a good choice, e.g.
START people = node:people_index(name="E*") MATCH people-[r]->() return people.name, r.age order by r.age asc
in order to return data on both the node and the relationships.
Sure, that's easily possible with the Neo4j query language Cypher.
For example:
start cat=node:Types(name='Person')
match cat<-[:IS_A]-person-[born:BORN]->city
where person.age > 30
return person.name, person.age, born.date, city.name
order by person.age asc
limit 10
You can experiment with it in our cypher console.

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