neo4j cypher Match 命令连接

这两个 Chypher 语句是否相同:

//first
match (a)-[r]->(b),b-[r2]->c

//second
match (a)-[r]->(b)
match b-[r2]->c

最佳答案

2 个 Cypher 语句不相同。我们可以使用 PROFILE command 来展示这一点，它向您展示了 Cypher 引擎将如何执行查询。

在以下示例中，查询都以 RETURN a, c 结尾，因为您不能有一个裸露的 MATCH 子句。

如您所见，第一个查询具有第二个查询没有的 NOT(r == r2) 过滤器。这是因为 Cypher 确保单个 MATCH 子句的结果不包含重复的关系。

第一个查询

profile match (a)-[r]->(b),b-[r2]->c return a,c;
==> +-----------------------------------------------+
==> | a                     | c                     |
==> +-----------------------------------------------+
==> | Node[1]{name:"World"} | Node[0]{name:"World"} |
==> +-----------------------------------------------+
==> 1 row
==> 2 ms
==>
==> Compiler CYPHER 2.3
==>
==> Planner COST
==>
==> Runtime INTERPRETED
==>
==> Projection
==>   |
==>   +Filter
==>     |
==>     +Expand(All)(0)
==>       |
==>       +Expand(All)(1)
==>         |
==>         +AllNodesScan
==>
==> +----------------+---------------+------+--------+----------------+----------------+
==> |       Operator | EstimatedRows | Rows | DbHits |    Identifiers |          Other |
==> +----------------+---------------+------+--------+----------------+----------------+
==> |     Projection |             1 |    1 |      0 | a, b, c, r, r2 |           a; c |
==> |         Filter |             1 |    1 |      0 | a, b, c, r, r2 |   NOT(r == r2) |
==> | Expand(All)(0) |             1 |    2 |      4 | a, b, c, r, r2 | (b)-[r2:]->(c) |
==> | Expand(All)(1) |             2 |    2 |      8 |        a, b, r |  (b)<-[r:]-(a) |
==> |   AllNodesScan |             6 |    6 |      7 |              b |                |
==> +----------------+---------------+------+--------+----------------+----------------+
==>

第二个查询

profile match (a)-[r]->(b) match b-[r2]->c return a,c;
==> +-----------------------------------------------+
==> | a                     | c                     |
==> +-----------------------------------------------+
==> | Node[1]{name:"World"} | Node[1]{name:"World"} |
==> | Node[1]{name:"World"} | Node[0]{name:"World"} |
==> +-----------------------------------------------+
==> 2 rows
==> 2 ms
==>
==> Compiler CYPHER 2.3
==>
==> Planner COST
==>
==> Runtime INTERPRETED
==>
==> Projection
==>   |
==>   +Expand(All)(0)
==>     |
==>     +Expand(All)(1)
==>       |
==>       +AllNodesScan
==>
==> +----------------+---------------+------+--------+----------------+----------------+
==> |       Operator | EstimatedRows | Rows | DbHits |    Identifiers |          Other |
==> +----------------+---------------+------+--------+----------------+----------------+
==> |     Projection |             1 |    2 |      0 | a, b, c, r, r2 |           a; c |
==> | Expand(All)(0) |             1 |    2 |      4 | a, b, c, r, r2 | (b)-[r2:]->(c) |
==> | Expand(All)(1) |             2 |    2 |      8 |        a, b, r |  (b)<-[r:]-(a) |
==> |   AllNodesScan |             6 |    6 |      7 |              b |                |
==> +----------------+---------------+------+--------+----------------+----------------+

关于neo4j cypher Match 命令连接，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/31001752/