更新：跟进blog post已发布。
这是我们为客户建模数据集时的常见问题，也是 Active/NonActive 实体的典型用例。
这是关于我对 Neo4j2.1.6 的体验的一些反馈：
第 1 点。在标签或索引属性上匹配并返回节点之间的数据库访问不会有差异
第2点。当这些节点位于模式的末尾时会遇到差异，例如
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:"hayes.shaina@yahoo.com"} | 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
在这种情况下，Cypher 不会使用索引 :Post(published)。
因此，在您有 ActivePost 标签的情况下，使用标签的性能更高，例如：
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:"hayes.shaina@yahoo.com"} | 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
第 3 点。始终使用标签表示肯定，这意味着对于上述情况，拥有 Draft 标签将迫使您执行以下查询：
MATCH (n:User {id:1})
WITH n
MATCH (n)-[:POST]->(post:Post)
WHERE NOT post :Draft
RETURN n, collect(post) as posts;
这意味着 Cypher 将打开每个节点标签标题并对其进行过滤。
第 4 点。避免需要在多个标签上进行匹配
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:"hayes.shaina@yahoo.com"} | 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
这将导致 Cypher 的过程与第 3 点相同。
第 5 点。如果可能，通过具有良好类型的命名关系来避免在标签上匹配
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:"hayes.shaina@yahoo.com"} | 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
性能会更高，因为它会利用图表的所有力量，并且只遵循节点的关系，从而导致数据库访问不超过匹配用户节点，因此不会对标签进行过滤。
这是我的 0,02€