neo4j 密码匹配命令连接

Posted 2023-03-29

【中文标题】neo4j 密码匹配命令连接

【英文标题】：neo4j cypher Match command concatenation

【发布时间】：2015-06-23 11:38:07

【问题描述】：

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

【问题讨论】：

是的，它们是相同的

【参考方案1】：

这 2 个 Cypher 语句并不相同。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，因为您不能有一个空的 MATCH 子句。

如您所见，第一个查询有一个 NOT(r == r2) 过滤器，而第二个查询没有。这是因为 Cypher 确保单个 MATCH 子句的结果不包含重复关系。

第一次查询

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 |                |
==> +----------------+---------------+------+--------+----------------+----------------+
==> 

第二次查询

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 |                |
==> +----------------+---------------+------+--------+----------------+----------------+

【讨论】：

哇，这真是太棒了，谢谢！我刚刚检查了一下，(a)-[r]->(b),b-[r2]->c 似乎与PROFILE 和(a)-[r]->(b)-[r2]->c 相同，这是有道理的。