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 语句并不相同。我们可以使用 PROFILE command 来显示这一点,它向您展示了 Cypher 引擎将如何执行查询。
在下面的示例中,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 | | ==> +----------------+---------------+------+--------+----------------+----------------+
关于neo4j cypher 匹配命令串联,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/31001752/