CYPHER 2.3 在 Neo4j 查询中的性能

Question

我在 Neo4j 查询中遇到问题。 假设我有一个名为 App 的节点类型。 App 节点具有字段“m_id”和“info”。 我想构建一个查询来创建字段“信息”相等的节点之间的关系。

这是查询：

MATCH (a:App {m_id:'SOME_VALUE' }),(b:App {info: a.info}) WHERE ID(a)<>ID(b) AND NOT (b)-[:INFO]->(a) MERGE (a)-[r:INFO]->(b) RETURN b.m_id;

我也有两个字段的索引：

CREATE CONSTRAINT ON (a:App) ASSERT a.m_id IS UNIQUE;
CREATE INDEX ON :App(info);

但问题是我的查询速度非常慢，可以访问 App 节点的所有记录。

这是查询的配置文件：

+---------------+--------+---------+-----------------+--------------------------------------------------------------------------------------------------------------------------------+
| Operator      | Rows   | DB Hits | Identifiers     | Other                                                                                                                          |
+---------------+--------+---------+-----------------+--------------------------------------------------------------------------------------------------------------------------------+
| +ColumnFilter |      0 |       0 | b.m_id          | keep columns b.m_id                                                                                                            |
| |             +--------+---------+-----------------+--------------------------------------------------------------------------------------------------------------------------------+
| +Extract      |      0 |       0 | a, b, b.m_id, r | b.m_id                                                                                                                         |
| |             +--------+---------+-----------------+--------------------------------------------------------------------------------------------------------------------------------+
| +Merge(Into)  |      0 |       1 | a, b, r         | (a)-[r:INFO]->(b)                                                                                                             |
| |             +--------+---------+-----------------+--------------------------------------------------------------------------------------------------------------------------------+
| +Eager        |      0 |       0 | a, b            |                                                                                                                                |
| |             +--------+---------+-----------------+--------------------------------------------------------------------------------------------------------------------------------+
| +Filter       |      0 |  2000000 | a, b            | Ands(b.info == a.info, NOT(IdFunction(a) == IdFunction(b)), NOT(nonEmpty(PathExpression((b)-[anon[104]:INFO]->(a), true)))) |
| |             +--------+---------+-----------------+--------------------------------------------------------------------------------------------------------------------------------+
| +SchemaIndex  | 184492 |  1000000 | a, b            | {  AUTOSTRING0}; :App(m_id)                                                                                                    |
| |             +--------+---------+-----------------+--------------------------------------------------------------------------------------------------------------------------------+
| +NodeByLabel  | 184492 |  1000001 | b               | :App                                                                                                                           |
+---------------+--------+---------+-----------------+--------------------------------------------------------------------------------------------------------------------------------+

Answer 1

尝试自行查找a ，使用WITH子句将a.info放入一个临时变量中，该变量由b的单独MATCH子句使用，如下所示：

MATCH (a:App { m_id:'SOME_VALUE' })
WITH a, a.info AS a_info
MATCH (b:App { info: a_info })
WHERE a <> b AND NOT (b)-[:INFO]->(a)
MERGE (a)-[r:INFO]->(b)
RETURN b.m_id;

在比较 2 个节点的属性时，似乎不使用索引。 使用a_info消除了这个障碍。

如果上面的配置文件显示未使用一个或两个索引，您可以尝试添加索引提示：

MATCH (a:App { m_id:'SOME_VALUE' })
USING INDEX a:App(m_id)
WITH a, a.info AS a_info
MATCH (b:App { info: a_info })
USING INDEX b:App(info)
WHERE a <> b AND NOT (b)-[:INFO]->(a)
MERGE (a)-[r:INFO]->(b)
RETURN b.m_id;

Answer 2

我想出了一个使用 OPTIONAL MATCH 的解决方案：

MATCH (a:App {m_id:'SOME_VALUE' }) OPTIONAL MATCH (a),(b:App {info: a.info}) WHERE ID(a)<>ID(b) AND NOT (b)-[:信息]->(a) 合并 (a)-[r:INFO]->(b) 返回 b.m_id;

这是查询的配置文件：

+----------------+------+---------+-----------------+------------------------------------------------------------------------------------------------------------+
| Operator       | Rows | DB Hits | Identifiers     | Other                                                                                                      |
+----------------+------+---------+-----------------+------------------------------------------------------------------------------------------------------------+
| +ColumnFilter  |    0 |       0 | b.m_id          | keep columns b.m_id                                                                                        |
| |              +------+---------+-----------------+------------------------------------------------------------------------------------------------------------+
| +Extract       |    0 |       0 | a, b, b.m_id, r | b.m_id                                                                                                     |
| |              +------+---------+-----------------+------------------------------------------------------------------------------------------------------------+
| +Merge(Into)   |    0 |       1 | a, b, r         | (a)-[r:INFO]->(b)                                                                                         |
| |              +------+---------+-----------------+------------------------------------------------------------------------------------------------------------+
| +Eager         |    0 |       0 | a, b            |                                                                                                            |
| |              +------+---------+-----------------+------------------------------------------------------------------------------------------------------------+
| +OptionalMatch |    0 |       0 | a, b            |                                                                                                            |
| |\             +------+---------+-----------------+------------------------------------------------------------------------------------------------------------+
| | +Filter      |    0 |       0 | a, b            | Ands(NOT(IdFunction(a) == IdFunction(b)), NOT(nonEmpty(PathExpression((b)-[anon[109]:INFO]->(a), true)))) |
| | |            +------+---------+-----------------+------------------------------------------------------------------------------------------------------------+
| | +SchemaIndex |    0 |       0 | a, b            | a.info; :App(info)                                                                                       |
| | |            +------+---------+-----------------+------------------------------------------------------------------------------------------------------------+
| | +Argument    |    0 |       0 | a               |                                                                                                            |
| |              +------+---------+-----------------+------------------------------------------------------------------------------------------------------------+
| +SchemaIndex   |    0 |       1 | a               | {  AUTOSTRING0}; :App(m_id)                                                                                |
+----------------+------+---------+-----------------+------------------------------------------------------------------------------------------------------------+