Neo4j 这两个密码查询之间有什么区别？

我有点不知所措

在我的数据库中，我的关系如下：

(u:User)-[r1:LISTENS_TO]->(a:Artist)<-[r2:LISTENS_TO]-(u2:User)

我很沮丧。看起来这并不需要20秒

后来我又回到这个问题上来，并尝试从一开始就调试它

我开始分解查询，我注意到我得到的结果要快得多。如果没有Neo4J空间查询，我只需1.5秒就可以得到结果

我最终添加了一些内容，并以以下查询结束：

START u=node(553314), u2=node:userLocations("withinDistance:[38.89037,-77.03196,80.467]")

OPTIONAL MATCH 
    pMutualArtists=(u:User)-[ar1:LISTENS_TO]->(a:Artist)<-[ar2:LISTENS_TO]-(u2:User)
WHERE
    u2:User

WITH u2, COUNT(DISTINCT pMutualArtists) AS mutualArtists

ORDER BY mutualArtists DESC
LIMIT 10
RETURN u2.username, mutualArtists

为了证明我连续运行了两次，得到了非常不同的结果：

neo4j-sh (?)$ START u=node(553314), u2=node:userLocations("withinDistance:[38.89037,-77.03196,80.467]")
>
> OPTIONAL MATCH
>     pMutualArtists=(u:User)-[ar1:LISTENS_TO]->(a:Artist)<-[ar2:LISTENS_TO]-(u2:User)
> WHERE
>     u2:User
>
> WITH u2, COUNT(DISTINCT pMutualArtists) AS mutualArtists
> ORDER BY mutualArtists DESC
> LIMIT 10
> RETURN u2.username, mutualArtists
> ;
+------------------------------+
| u2.username  | mutualArtists |
+------------------------------+
| "573904765"  | 644           |
| "28600291"   | 601           |
| "1092510304" | 558           |
| "1367963461" | 521           |
| "1508790199" | 455           |
| "1335360028" | 447           |
| "18200866"   | 444           |
| "1229430376" | 435           |
| "748318333"  | 434           |
| "5612902"    | 431           |
+------------------------------+
10 rows
4240 ms
neo4j-sh (?)$ START me=node(553314), other=node:userLocations("withinDistance:[38.89037,-77.03196,80.467]")
>
> OPTIONAL MATCH
>     pMutualArtists=(me:User)-[ar1:LISTENS_TO]->(a:Artist)<-[ar2:LISTENS_TO]-(other:User)
> WHERE
>     other:User
>
> WITH other, COUNT(DISTINCT pMutualArtists) AS mutualArtists
> ORDER BY mutualArtists DESC
> LIMIT 10
> RETURN other.username, mutualArtists;
+--------------------------------+
| other.username | mutualArtists |
+--------------------------------+
| "573904765"    | 644           |
| "28600291"     | 601           |
| "1092510304"   | 558           |
| "1367963461"   | 521           |
| "1508790199"   | 455           |
| "1335360028"   | 447           |
| "18200866"     | 444           |
| "1229430376"   | 435           |
| "748318333"    | 434           |
| "5612902"      | 431           |
+--------------------------------+
10 rows
20418 ms

neo4j sh（？）
>
>选配
>pMutualArtists=（u:User）-[ar1:LISTENS\u TO]->（a:Artist）其中
>u2：用户
>
>对于u2，将（不同的pMutualArtists）计数为mutualArtists
>共同主义者的命令描述
>限制10
>返回u2.username，mutualArtists
> ;
+------------------------------+
|u2.username |共同主义者|
+------------------------------+
| "573904765"  | 644           |
| "28600291"   | 601           |
| "1092510304" | 558           |
| "1367963461" | 521           |
| "1508790199" | 455           |
| "1335360028" | 447           |
| "18200866"   | 444           |
| "1229430376" | 435           |
| "748318333"  | 434           |
| "5612902"    | 431           |
+------------------------------+
10排
4240毫秒
neo4j sh（？）$START me=node（553314），other=node:userLocations（“withindance:[38.89037，-77.03196,80.467]”）
>
>选配
>pMutualArtists=（me:User）-[ar1:LISTENS\u TO]->（a:Artist）其中
>其他：用户
>
>对于其他，将（不同的pmutualarists）计数为mutualArtists
>共同主义者的命令描述
>限制10
>返回other.username，mutualArtists；
+--------------------------------+
|other.username |互惠主义者|
+--------------------------------+
| "573904765"    | 644           |
| "28600291"     | 601           |
| "1092510304"   | 558           |
| "1367963461"   | 521           |
| "1508790199"   | 455           |
| "1335360028"   | 447           |
| "18200866"     | 444           |
| "1229430376"   | 435           |
| "748318333"    | 434           |
| "5612902"      | 431           |
+--------------------------------+
10排
20418毫秒

除非我发疯了，否则这两个查询之间唯一的区别就是节点的名称（我将“me”改为“u”，将“other”改为“u2”）

为什么这会导致5倍的改善

如果有人对此有任何见解，我将永远感激

谢谢

-亚当

---

编辑8.1.14

根据@ulkas的建议，我尝试简化查询

结果是：

START u=node(553314), u2=node:userLocations("withinDistance:[38.89037,-77.03196,80.467]")
OPTIONAL MATCH pMutualArtists=(u:User)-[ar1:LISTENS_TO]->(a:Artist)<-[ar2:LISTENS_TO]-(u2:User)
RETURN u2.username, COUNT(DISTINCT pMutualArtists) as mutualArtists
ORDER BY mutualArtists DESC
LIMIT 10

START u=node（553314），u2=node:userLocations（“withindance:[38.89037，-77.03196,80.467]”）
可选匹配pMutualArtists=（u:User）-[ar1:LISTENS\u TO]->（a:Artist）（a:Artist）这听起来像是看到了缓存的效果。第一次访问时，缓存未填充。由于缓存中已存在节点/关系，因此命中同一图形的后续查询速度会快得多。
在
之后使用
可选匹配
，其中other:User
没有意义，因为结束节点
other
（
u2
）必须匹配。尝试在不使用
可选匹配
和
where
的情况下执行查询，并且在不使用最后一个
的情况下使用
，只需

START me=node(553314), other=node:userLocations("withinDistance[38.89037,-77.03196,80.467]")
 MATCH
     pMutualArtists=(me:User)-[ar1:LISTENS_TO]->(a:Artist)<-[ar2:LISTENS_TO]-(other:User)   
 RETURN other.username, count(DISTINCT pMutualArtists) as mutualArtists
 ORDER BY mutualArtists DESC
 LIMIT 10

START me=node（553314），other=node:userLocations（“withindance[38.89037，-77.03196,80.467]”）
匹配
pMutualArtists=（me:User）-[ar1:LISTENS\u TO]->（a:Artist）感谢您的回复。这正是我所想的。但是我可以在一行中多次运行长查询（与我一起运行的查询和其他查询）并获得相同的结果，而在一行中多次运行其他查询也会产生相同的结果。此外，这些结果会在服务器重新启动之间持续存在。感谢您的回复。我同意“WHERE”和“WITH”条款是没有必要的。这些都是我一直在尝试的东西。但是，对于我的特定用例，“可选匹配”是必要的，因为我需要返回没有共同艺术家的其他用户，而“匹配”不会返回。我将编辑我上面的帖子，并根据你的评论告诉你我尝试了什么；博士…同样的问题。我明白了，我也很困惑为什么会这样。看这个问题。
neo4j-sh (?)$ START u=node(553314), u2=node:userLocations("withinDistance:[38.89037,-77.03196,80.467]")
>
> OPTIONAL MATCH
>     pMutualArtists=(u:User)-[ar1:LISTENS_TO]->(a:Artist)<-[ar2:LISTENS_TO]-(u2:User)
> WHERE
>     u2:User
>
> WITH u2, COUNT(DISTINCT pMutualArtists) AS mutualArtists
> ORDER BY mutualArtists DESC
> LIMIT 10
> RETURN u2.username, mutualArtists
> ;
+------------------------------+
| u2.username  | mutualArtists |
+------------------------------+
| "573904765"  | 644           |
| "28600291"   | 601           |
| "1092510304" | 558           |
| "1367963461" | 521           |
| "1508790199" | 455           |
| "1335360028" | 447           |
| "18200866"   | 444           |
| "1229430376" | 435           |
| "748318333"  | 434           |
| "5612902"    | 431           |
+------------------------------+
10 rows
4240 ms
neo4j-sh (?)$ START me=node(553314), other=node:userLocations("withinDistance:[38.89037,-77.03196,80.467]")
>
> OPTIONAL MATCH
>     pMutualArtists=(me:User)-[ar1:LISTENS_TO]->(a:Artist)<-[ar2:LISTENS_TO]-(other:User)
> WHERE
>     other:User
>
> WITH other, COUNT(DISTINCT pMutualArtists) AS mutualArtists
> ORDER BY mutualArtists DESC
> LIMIT 10
> RETURN other.username, mutualArtists;
+--------------------------------+
| other.username | mutualArtists |
+--------------------------------+
| "573904765"    | 644           |
| "28600291"     | 601           |
| "1092510304"   | 558           |
| "1367963461"   | 521           |
| "1508790199"   | 455           |
| "1335360028"   | 447           |
| "18200866"     | 444           |
| "1229430376"   | 435           |
| "748318333"    | 434           |
| "5612902"      | 431           |
+--------------------------------+
10 rows
20418 ms

START u=node(553314), u2=node:userLocations("withinDistance:[38.89037,-77.03196,80.467]")
OPTIONAL MATCH pMutualArtists=(u:User)-[ar1:LISTENS_TO]->(a:Artist)<-[ar2:LISTENS_TO]-(u2:User)
RETURN u2.username, COUNT(DISTINCT pMutualArtists) as mutualArtists
ORDER BY mutualArtists DESC
LIMIT 10

START me=node(553314), other=node:userLocations("withinDistance:[38.89037,-77.03196,80.467]")
OPTIONAL MATCH pMutualArtists=(me:User)-[ar1:LISTENS_TO]->(a:Artist)<-[ar2:LISTENS_TO]-(other:User)
RETURN other.username, COUNT(DISTINCT pMutualArtists) as mutualArtists
ORDER BY mutualArtists DESC
LIMIT 10

START me=node(553314), other=node:userLocations("withinDistance[38.89037,-77.03196,80.467]")
 MATCH
     pMutualArtists=(me:User)-[ar1:LISTENS_TO]->(a:Artist)<-[ar2:LISTENS_TO]-(other:User)   
 RETURN other.username, count(DISTINCT pMutualArtists) as mutualArtists
 ORDER BY mutualArtists DESC
 LIMIT 10