Neo4j: label vs. indexed property?

Question

Suppose you're Twitter, and:

• You have (:User) and (:Tweet) nodes;
• Tweets can get flagged; and
• You want to query the list of flagged tweets currently awaiting moderation.

You can either add a label for those tweets, e.g. :AwaitingModeration, or add and index a property, e.g. isAwaitingModeration = true|false.

Is one option inherently better than the other?

I know the best answer is probably to try and load test both :), but is there anything from Neo4j's implementation POV that makes one option more robust or suited for this kind of query?

Does it depend on the volume of tweets in this state at any given moment? If it's in the 10s vs. the 1000s, does that make a difference?

My impression is that labels are better suited for a large volume of nodes, whereas indexed properties are better for smaller volumes (ideally, unique nodes), but I'm not sure if that's actually true.

Thanks!

Answer 1

UPDATE: Follow up blog post published.

This is a common question when we model datasets for customers and a typical use case for Active/NonActive entities.

This is a little feedback about what I've experienced valid for Neo4j2.1.6 :

Point 1. You will not have difference in db accesses between matching on a label or on an indexed property and return the nodes

Point 2. The difference will be encountered when such nodes are at the end of a pattern, for example

MATCH (n:User {id:1})
WITH n
MATCH (n)-[:WRITTEN]->(post:Post)
WHERE post.published = true
RETURN n, collect(post) as posts;

-

PROFILE MATCH (n:User) WHERE n._id = 'c084e0ca-22b6-35f8-a786-c07891f108fc'
> WITH n
> MATCH (n)-[:WRITTEN]->(post:BlogPost)
> WHERE post.active = true
> RETURN n, size(collect(post)) as posts;
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| n                                                                                                                                                         | posts |
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Node[118]{_id:"c084e0ca-22b6-35f8-a786-c07891f108fc",login:"joy.wiza",password:"7425b990a544ae26ea764a4473c1863253240128",email:"[e-mail]"} | 1     |
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row

ColumnFilter(0)
  |
  +Extract
    |
    +ColumnFilter(1)
      |
      +EagerAggregation
        |
        +Filter
          |
          +SimplePatternMatcher
            |
            +SchemaIndex

+----------------------+------+--------+----------------------+----------------------------------------------------------------------------+
|             Operator | Rows | DbHits |          Identifiers |                                                                      Other |
+----------------------+------+--------+----------------------+----------------------------------------------------------------------------+
|      ColumnFilter(0) |    1 |      0 |                      |                                                      keep columns n, posts |
|              Extract |    1 |      0 |                      |                                                                      posts |
|      ColumnFilter(1) |    1 |      0 |                      |                                           keep columns n,   AGGREGATION153 |
|     EagerAggregation |    1 |      0 |                      |                                                                          n |
|               Filter |    1 |      3 |                      | (hasLabel(post:BlogPost(1)) AND Property(post,active(8)) == {  AUTOBOOL1}) |
| SimplePatternMatcher |    1 |     12 | n, post,   UNNAMED84 |                                                                            |
|          SchemaIndex |    1 |      2 |                 n, n |                                                {  AUTOSTRING0}; :User(_id) |
+----------------------+------+--------+----------------------+----------------------------------------------------------------------------+

Total database accesses: 17

In this case, Cypher will not make use of the index :Post(published).

Thus the use of labels is more performant in the case you have a ActivePost label for e.g. :

neo4j-sh (?)$ PROFILE MATCH (n:User) WHERE n._id = 'c084e0ca-22b6-35f8-a786-c07891f108fc'
> WITH n
> MATCH (n)-[:WRITTEN]->(post:ActivePost)
> RETURN n, size(collect(post)) as posts;
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| n                                                                                                                                                         | posts |
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Node[118]{_id:"c084e0ca-22b6-35f8-a786-c07891f108fc",login:"joy.wiza",password:"7425b990a544ae26ea764a4473c1863253240128",email:"[e-mail]"} | 1     |
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row

ColumnFilter(0)
  |
  +Extract
    |
    +ColumnFilter(1)
      |
      +EagerAggregation
        |
        +Filter
          |
          +SimplePatternMatcher
            |
            +SchemaIndex

+----------------------+------+--------+----------------------+----------------------------------+
|             Operator | Rows | DbHits |          Identifiers |                            Other |
+----------------------+------+--------+----------------------+----------------------------------+
|      ColumnFilter(0) |    1 |      0 |                      |            keep columns n, posts |
|              Extract |    1 |      0 |                      |                            posts |
|      ColumnFilter(1) |    1 |      0 |                      | keep columns n,   AGGREGATION130 |
|     EagerAggregation |    1 |      0 |                      |                                n |
|               Filter |    1 |      1 |                      |     hasLabel(post:ActivePost(2)) |
| SimplePatternMatcher |    1 |      4 | n, post,   UNNAMED84 |                                  |
|          SchemaIndex |    1 |      2 |                 n, n |      {  AUTOSTRING0}; :User(_id) |
+----------------------+------+--------+----------------------+----------------------------------+

Total database accesses: 7

Point 3. Always use labels for positives, meaning for the case above, having a Draft label will force you to execute the following query :

MATCH (n:User {id:1})
WITH n
MATCH (n)-[:POST]->(post:Post)
WHERE NOT post :Draft
RETURN n, collect(post) as posts;

Meaning that Cypher will open each node label headers and do a filter on it.

Point 4. Avoid having the need to match on multiple labels

MATCH (n:User {id:1})
WITH n
MATCH (n)-[:POST]->(post:Post:ActivePost)
RETURN n, collect(post) as posts;

neo4j-sh (?)$ PROFILE MATCH (n:User) WHERE n._id = 'c084e0ca-22b6-35f8-a786-c07891f108fc'
> WITH n
> MATCH (n)-[:WRITTEN]->(post:BlogPost:ActivePost)
> RETURN n, size(collect(post)) as posts;
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| n                                                                                                                                                         | posts |
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Node[118]{_id:"c084e0ca-22b6-35f8-a786-c07891f108fc",login:"joy.wiza",password:"7425b990a544ae26ea764a4473c1863253240128",email:"[e-mail]"} | 1     |
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row

ColumnFilter(0)
  |
  +Extract
    |
    +ColumnFilter(1)
      |
      +EagerAggregation
        |
        +Filter
          |
          +SimplePatternMatcher
            |
            +SchemaIndex

+----------------------+------+--------+----------------------+---------------------------------------------------------------+
|             Operator | Rows | DbHits |          Identifiers |                                                         Other |
+----------------------+------+--------+----------------------+---------------------------------------------------------------+
|      ColumnFilter(0) |    1 |      0 |                      |                                         keep columns n, posts |
|              Extract |    1 |      0 |                      |                                                         posts |
|      ColumnFilter(1) |    1 |      0 |                      |                              keep columns n,   AGGREGATION139 |
|     EagerAggregation |    1 |      0 |                      |                                                             n |
|               Filter |    1 |      2 |                      | (hasLabel(post:BlogPost(1)) AND hasLabel(post:ActivePost(2))) |
| SimplePatternMatcher |    1 |      8 | n, post,   UNNAMED84 |                                                               |
|          SchemaIndex |    1 |      2 |                 n, n |                                   {  AUTOSTRING0}; :User(_id) |
+----------------------+------+--------+----------------------+---------------------------------------------------------------+

Total database accesses: 12

This will result in the same process for Cypher that on point 3.

Point 5. If possible, avoid the need to match on labels by having well typed named relationships

MATCH (n:User {id:1})
WITH n
MATCH (n)-[:PUBLISHED]->(p)
RETURN n, collect(p) as posts

-

MATCH (n:User {id:1})
WITH n
MATCH (n)-[:DRAFTED]->(post)
RETURN n, collect(post) as posts;

neo4j-sh (?)$ PROFILE MATCH (n:User) WHERE n._id = 'c084e0ca-22b6-35f8-a786-c07891f108fc'
> WITH n
> MATCH (n)-[:DRAFTED]->(post)
> RETURN n, size(collect(post)) as posts;
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| n                                                                                                                                                         | posts |
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Node[118]{_id:"c084e0ca-22b6-35f8-a786-c07891f108fc",login:"joy.wiza",password:"7425b990a544ae26ea764a4473c1863253240128",email:"[e-mail]"} | 3     |
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row

ColumnFilter(0)
  |
  +Extract
    |
    +ColumnFilter(1)
      |
      +EagerAggregation
        |
        +SimplePatternMatcher
          |
          +SchemaIndex

+----------------------+------+--------+----------------------+----------------------------------+
|             Operator | Rows | DbHits |          Identifiers |                            Other |
+----------------------+------+--------+----------------------+----------------------------------+
|      ColumnFilter(0) |    1 |      0 |                      |            keep columns n, posts |
|              Extract |    1 |      0 |                      |                            posts |
|      ColumnFilter(1) |    1 |      0 |                      | keep columns n,   AGGREGATION119 |
|     EagerAggregation |    1 |      0 |                      |                                n |
| SimplePatternMatcher |    3 |      0 | n, post,   UNNAMED84 |                                  |
|          SchemaIndex |    1 |      2 |                 n, n |      {  AUTOSTRING0}; :User(_id) |
+----------------------+------+--------+----------------------+----------------------------------+

Total database accesses: 2

Will be more performant, because it will use all the power of the graph and just follow the relationships from the node resulting in no more db accesses than matching the user node and thus no filtering on labels.

This was my 0,02€